Bump version to v2026.9.16.2

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.21)
 
-project(OrbitHub VERSION 2026.9.8.3 LANGUAGES CXX)
+project(OrbitHub VERSION 2026.9.16.2 LANGUAGES CXX)
 
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
@@ -12,10 +12,24 @@ set(CMAKE_AUTORCC ON)
 
 include(GNUInstallDirs)
 
-find_package(Qt6 6.2 REQUIRED COMPONENTS Widgets Sql)
+find_package(Qt6 6.2 REQUIRED COMPONENTS Widgets Sql Network)
+find_package(OpenSSL REQUIRED)
+find_package(ZLIB REQUIRED)
+find_package(JPEG REQUIRED)
 
 qt_standard_project_setup()
 
+option(ORBITHUB_BUILD_TESTS "Build unit tests (requires Qt6::Test)" ON)
+if(ORBITHUB_BUILD_TESTS)
+    find_package(Qt6 6.2 QUIET COMPONENTS Test)
+    if(TARGET Qt6::Test)
+        enable_testing()
+    else()
+        message(STATUS "Qt6::Test not found -- skipping unit tests (set ORBITHUB_BUILD_TESTS=OFF to silence this)")
+        set(ORBITHUB_BUILD_TESTS OFF)
+    endif()
+endif()
+
 add_subdirectory(third_party/KodoTerm)
 
 if(NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/third_party/FreeRDP/CMakeLists.txt")
@@ -87,6 +101,8 @@ set(ORBITHUB_SOURCES
     src/app_icon.cpp
     src/app_icon.h
     src/main.cpp
+    src/mremoteng_importer.cpp
+    src/mremoteng_importer.h
     src/profile_dialog.cpp
     src/profile_dialog.h
     src/profile_repository.cpp
@@ -102,6 +118,8 @@ set(ORBITHUB_SOURCES
     src/session_tab.h
     src/rdp_display_widget.cpp
     src/rdp_display_widget.h
+    src/vnc_display_widget.cpp
+    src/vnc_display_widget.h
     src/terminal_view.cpp
     src/terminal_view.h
     src/session_window.cpp
@@ -110,6 +128,14 @@ set(ORBITHUB_SOURCES
     src/rdp_session_backend.h
     src/ssh_session_backend.cpp
     src/ssh_session_backend.h
+    src/vnc_session_backend.cpp
+    src/vnc_session_backend.h
+    src/vnc_pixel_codecs.cpp
+    src/vnc_pixel_codecs.h
+    src/vnc_apple_dh_auth.cpp
+    src/vnc_apple_dh_auth.h
+    src/vnc_apple_rsa_auth.cpp
+    src/vnc_apple_rsa_auth.h
     src/unsupported_session_backend.cpp
     src/unsupported_session_backend.h
 )
@@ -132,8 +158,12 @@ endif()
 
 add_executable(orbithub WIN32 MACOSX_BUNDLE ${ORBITHUB_SOURCES})
 
-target_link_libraries(orbithub PRIVATE Qt6::Widgets Qt6::Sql)
+target_link_libraries(orbithub PRIVATE Qt6::Widgets Qt6::Sql Qt6::Network)
 target_link_libraries(orbithub PRIVATE KodoTerm::KodoTerm)
+target_link_libraries(orbithub PRIVATE OpenSSL::Crypto)
+target_link_libraries(orbithub PRIVATE ZLIB::ZLIB)
+target_link_libraries(orbithub PRIVATE JPEG::JPEG)
+target_compile_definitions(orbithub PRIVATE ORBITHUB_VERSION_STRING="${PROJECT_VERSION}")
 if(TARGET freerdp AND TARGET winpr)
     target_compile_definitions(orbithub PRIVATE ORBITHUB_HAS_FREERDP)
     target_include_directories(orbithub PRIVATE
@@ -271,3 +301,7 @@ install(FILES third_party/KodoTerm/LICENSE
     DESTINATION ${CMAKE_INSTALL_DATADIR}/licenses/org.darksingularity.OrbitHub
     RENAME LICENSE-KodoTerm
 )
+
+if(ORBITHUB_BUILD_TESTS)
+    add_subdirectory(tests)
+endif()

README.md

@@ -13,17 +13,18 @@ Supported target platforms:
 
 OrbitHub is in active development.
 
-- Milestones completed: M0-M5, and M7-M9
+- Milestones completed: M0-M9
 - Current milestone: Milestone 10 (v1.0 Stabilization)
-- Deferred milestone: Milestone 6 (VNC Fully Working)
+- Latest checkpoint tag: `v2026.9.15`
-- Latest checkpoint tag: `v2026.9.8.3`
+- VNC (M6) covers standard VNC Authentication and no-auth servers; see
-- VNC implementation milestone (M6) is currently deferred
+  [docs/PROGRESS.md](docs/PROGRESS.md) for known gaps (Apple Screen
+  Sharing auth, compression encodings, resize, cursor sync, clipboard)
 
 Progress and milestone details:
 - [docs/PROGRESS.md](docs/PROGRESS.md)
 
 Latest release (installers for Windows, Linux, and macOS):
-- [v2026.9.8.3](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.8.3)
+- [v2026.9.15](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.15)
 
 User Guide:
 - [docs/USER_GUIDE.md](docs/USER_GUIDE.md) (also available as a PDF attached to each release, and in-app via `Help -> User Guide`)
@@ -181,4 +182,6 @@ See in-app `Help -> About OrbitHub` for license links and third-party inventory.
 ## Notes
 
 - Passwords are requested at connect time and are not stored in the profile database.
-- This repository currently prioritizes integrated SSH and RDP workflows while VNC implementation is pending.
+- VNC support covers standard VNC Authentication and no-auth servers (e.g. TigerVNC, x11vnc,
+  TightVNC); it doesn't yet reach macOS's built-in Screen Sharing server, which uses a different
+  authentication scheme (see docs/PROGRESS.md, Milestone 6).

docs/BUILDING.md

@@ -17,7 +17,7 @@ sudo apt update
 sudo apt install -y \
   build-essential cmake ninja-build git pkg-config \
   qt6-base-dev qt6-base-dev-tools qt6-tools-dev qt6-tools-dev-tools \
-  openssh-client libssl-dev zlib1g-dev
+  openssh-client libssl-dev zlib1g-dev libjpeg-turbo8-dev
 
 cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
 cmake --build build
@@ -29,11 +29,11 @@ cmake --build build
 ```bash
 xcode-select --install
 brew update
-brew install cmake ninja pkg-config qt@6 openssh openssl@3
+brew install cmake ninja pkg-config qt@6 openssh openssl@3 jpeg-turbo
 
 cmake -S . -B build -G Ninja \
   -DCMAKE_BUILD_TYPE=Release \
-  -DCMAKE_PREFIX_PATH="$(brew --prefix qt@6);$(brew --prefix openssl@3)"
+  -DCMAKE_PREFIX_PATH="$(brew --prefix qt@6);$(brew --prefix openssl@3);$(brew --prefix jpeg-turbo)"
 cmake --build build
 open build/orbithub.app
 ```
@@ -56,7 +56,7 @@ Install dependencies via vcpkg:
 ```powershell
 git clone https://github.com/microsoft/vcpkg C:\dev\vcpkg
 C:\dev\vcpkg\bootstrap-vcpkg.bat
-C:\dev\vcpkg\vcpkg.exe install qtbase:x64-windows openssl:x64-windows zlib:x64-windows
+C:\dev\vcpkg\vcpkg.exe install qtbase:x64-windows openssl:x64-windows zlib:x64-windows libjpeg-turbo:x64-windows
 ```
 
 Open `x64 Native Tools Command Prompt for VS 2022` (or Developer PowerShell), then build:
@@ -75,7 +75,7 @@ Run (ensures DLL paths from vcpkg are present):
 C:\dev\vcpkg\vcpkg.exe env --triplet x64-windows -- .\build\orbithub.exe
 ```
 
-If you already have `Qt 6` from the Qt installer and do not want vcpkg Qt, you can point CMake at that Qt install with `-DCMAKE_PREFIX_PATH=...`, but you still need compatible `OpenSSL` and `zlib` development libraries for the embedded FreeRDP build.
+If you already have `Qt 6` from the Qt installer and do not want vcpkg Qt, you can point CMake at that Qt install with `-DCMAKE_PREFIX_PATH=...`, but you still need compatible `OpenSSL`, `zlib`, and `libjpeg-turbo` development libraries (the first two for the embedded FreeRDP build; `libjpeg-turbo` for VNC's Tight encoding's JPEG sub-mode).
 
 ## Notes
 

docs/PROGRESS.md

@@ -102,16 +102,164 @@ Delivered:
 Git:
 - Tag: `v0-m5-done`
 
-## Milestone 6 - VNC Fully Working
+## Milestone 6 - VNC Working (initial scope)
 
-Status: Deferred (temporarily postponed)
+Status: Completed (initial scope; see gaps below)
 
-Planned Scope:
+Delivered:
-- Replace current unsupported VNC path with complete VNC implementation
+- `VncSessionBackend`: an original RFB (RFC 6143) client implementation
-- Deliver usable in-app VNC session behavior aligned to SSH/RDP UX
+  against `QTcpSocket` -- no permissively licensed VNC client library
-- Implement VNC connect/disconnect/reconnect lifecycle handling
+  exists to vendor the way FreeRDP was for RDP (LibVNCClient is GPLv2,
-- Extend profile/session connect options needed by VNC
+  gtk-vnc is LGPL but GTK-tied), so this is from-scratch protocol code,
-- Standardize event log and error mapping behavior with SSH/RDP
+  threaded like `SshSessionBackend` (a `QObject` on its own `QThread`
+  driven by Qt's own async socket signals) rather than `RdpSessionBackend`'s
+  manual worker-thread/blocking-loop pattern
+- Full connect/disconnect/reconnect lifecycle, RFB protocol-version
+  negotiation (3.3/3.7/3.8 handshake differences handled explicitly),
+  VNC Authentication (DES challenge-response, using OpenSSL's classic DES
+  API) and no-auth security types, Raw + CopyRect framebuffer decoding,
+  keyboard (Qt key -> X11 keysym mapping) and mouse/wheel input forwarding
+- `VncDisplayWidget` mirroring `RdpDisplayWidget`'s scale-to-fit rendering
+  and input-forwarding shape
+- 45 unit tests (`tests/test_vnc_session_backend.cpp`): pure-function
+  coverage (DES key prep verified against an independently documented test
+  vector, keysym mapping, socket-error mapping) plus state-machine
+  coverage against a scripted in-process fake RFB server (all three
+  protocol-version handshake shapes, auth success/failure, unsupported
+  security types, pixel-accurate Raw/Hextile/ZRLE/Tight decoding including
+  a ZRLE zlib-stream-persistence test across two separate
+  `FramebufferUpdate` messages, a Tight stream-reset-flag test, cursor/
+  clipboard round trips, both Apple auth schemes) -- caught and fixed a
+  real re-entrancy bug (`abort()` synchronously re-firing `disconnected()`
+  mid-`failConnection()`, silently overwriting a specific error with a
+  generic one) and a real Apple-DH wire-order bug (see below)
+- Verified live against a real, independently implemented VNC server
+  (TightVNC on Windows): connect with VNC Authentication, correct
+  framebuffer dimensions and pixel data, clean disconnect, reconnect,
+  live cursor-shape and clipboard-send checks. That particular server
+  consistently chose Raw for actual framebuffer content regardless of
+  which compression encodings were announced, so Hextile/ZRLE/Tight's
+  real-world decode path isn't independently confirmed live -- the unit
+  tests are the primary correctness evidence for those
+- Per-tab VNC-only display mode toggle (tab-bar right-click ->
+  `Display Mode`): `Scale to Fit` (default, matches RDP's behavior) or
+  `Actual Size (Scrollbars)` -- renders the remote framebuffer at its
+  native pixel size inside a `QScrollArea` so text isn't shrunk, at the
+  cost of needing to scroll to see the whole screen. Reuses
+  `VncDisplayWidget::renderRect()`'s existing scale-to-fit math unchanged:
+  it degenerates to an exact 1:1 mapping once the widget's own bounds are
+  fixed to the remote's size, so no separate rendering path was needed.
+  Persisted across sessions like the terminal theme preference.
+- Fixed a real, separate bug found during Apple-auth live testing:
+  `SessionTab::requestConnectOptions()` never prompted for a password on
+  VNC profiles at all (only SSH/RDP), so every VNC connection went out
+  with an empty password regardless of what the server needed. VNC now
+  gets its own prompt, with an empty password allowed through (unlike
+  RDP's hard requirement) since some VNC servers are no-auth and there's
+  no way to know that before the server's security-type negotiation
+- Profiles can now leave the username blank for every protocol (issue
+  #21): SSH/RDP previously hard-required one at profile-save time; that
+  validation is gone, and `SessionTab` now asks for it at connect time
+  instead (reusing the existing password-prompt bar in unmasked mode),
+  same as it already does for a blank password. VNC's username is only
+  ever asked for if the server's negotiated auth method actually needs
+  one -- plain VNC Authentication and no-auth never do, only the two
+  Apple schemes (30/33) do -- which happens *mid-connection*, after the
+  backend has already picked a security type, not before connecting like
+  SSH/RDP. This needed a new async request/response pair on
+  `SessionBackend` (`usernameRequested()` / `provideUsername()`,
+  mirroring the existing SSH host-key-confirmation pattern):
+  `VncSessionBackend` pauses its state machine mid-parse (without
+  consuming the already-buffered response bytes) and emits the request,
+  resuming once `SessionTab` answers; cancelling fails the connection
+  cleanly rather than sending Apple auth a blank username. The value is
+  kept on the tab's in-memory profile copy for its lifetime, not written
+  back to the saved profile
+- Robustness fix: an unrecognized `FramebufferUpdate` rectangle encoding
+  used to abort the connection generically; `kAnnouncedEncodings` is now
+  the single source of truth for what `SetEncodings` announces and what
+  the rectangle-dispatch `switch` can decode, with a regression test
+  pinning that every announced encoding has a working case
+- Clipboard sync (`ServerCutText`/`ClientCutText`, Latin-1 only -- no
+  Unicode extension) in both directions
+- Remote cursor shape sync via RFB's Cursor pseudo-encoding, mirroring
+  `RdpDisplayWidget`'s cursor handling in `VncDisplayWidget`
+- Hextile, ZRLE, and Tight compression encodings, in addition to Raw +
+  CopyRect -- meaningfully reduces bandwidth over slower links versus Raw
+  alone; Tight in particular is the encoding most real VNC servers prefer
+  when the client offers it. Pure tile/pixel decode logic (including
+  Tight's three filters -- Copy, Palette, Gradient) lives in
+  `src/vnc_pixel_codecs.h/.cpp`, kept separate from the wire-sequencing
+  state machine so it's unit-testable without a socket. ZRLE and Tight's
+  Basic mode share the same "persistent zlib stream(s), decompress
+  in-memory, decode synchronously" approach (Tight has 4 independent
+  streams selected per-rectangle, individually reset via the
+  compression-control byte's low 4 bits). Tight's JPEG sub-mode decodes
+  via libjpeg-turbo directly (`find_package(JPEG REQUIRED)` ->
+  `JPEG::JPEG`), not `QImage`'s own JPEG plugin, to avoid a
+  packaging-dependent runtime failure mode. ZRLE/Tight link `ZLIB::ZLIB`
+  (found via a fresh top-level `find_package(ZLIB REQUIRED)`, independent
+  of whether vendored FreeRDP's own internal zlib usage stays enabled)
+- Apple Screen Sharing authentication: two schemes, both undocumented by
+  Apple. Security type 30 (Diffie-Hellman + AES, `src/vnc_apple_dh_auth.h`)
+  is implemented and its wire format is confirmed correct against an
+  independent, authoritative source (`neatvnc`'s `rfb-proto.h` struct
+  definitions plus its full server-side verification code, cross-checked
+  field-by-field: generator/key-length framing, the
+  credentials-before-public-key send order -- an actual ordering bug
+  caught this way and fixed -- shared-secret derivation and padding, AES
+  key derivation, and the credential buffer layout all match exactly).
+  Security type 33 (RSA + AES, `src/vnc_apple_rsa_auth.h`) is also
+  implemented, sourced from the `asyncvnc` PyPI package, as a fallback.
+  Preference when both are offered: None > AppleDH(30) > AppleRSA(33) >
+  VNCAuth(2). Covered by a DH round-trip test, fake-server integration
+  tests for both schemes, a preference-order test, and a regression test
+  built from real bytes captured off an actual macOS server
+
+Known gaps and open issues (see issue #3 for follow-up tracking):
+- **Apple auth not yet confirmed working end-to-end against a real
+  server.** Live-tested against a macOS Tahoe (26.6.2) Screen Sharing
+  server with Screen Sharing correctly enabled and the connecting account
+  allowed: type 33 gets rejected by the server immediately after the
+  client's initial host-key request (before any credentials are even
+  sent), and type 30 -- despite matching the authoritative reference
+  byte-for-byte, verified via multiple independent diagnostic scripts --
+  still gets rejected with a generic "Authentication or authorization
+  failure" from the server. macOS Tahoe was released after this
+  assistant's knowledge cutoff, so there may be a protocol or permission-
+  model change specific to that OS version neither reference source
+  reflects; a `screensharingd` Console.app log from the moment of
+  rejection would be the next diagnostic step whenever this is picked
+  back up. Until this is resolved, treat both security types as
+  implemented-and-tested-in-isolation but **not verified to actually
+  authenticate against a real macOS server**
+- Tight's Basic compression mode always assumes zlib-compressed payloads;
+  the real protocol permits the server to skip compression for very small
+  (filtered byte count under ~12) payloads, which this decoder doesn't
+  special-case (the exact trigger/wire-signaling for that couldn't be
+  verified with confidence against the RFC text alone). In practice this
+  only affects rare, tiny rectangles -- solid or near-solid tiny areas are
+  virtually always sent as Fill instead -- and fails that one rectangle's
+  decode cleanly (disconnects with a clear error) rather than silently
+  misinterpreting it
+- Tight's Gradient filter is implemented from RFC 6143's description but
+  is the least exercised/confirmed of the three filters against a real
+  server in this pass (most real-world Tight traffic uses Copy or
+  Palette)
+- Packaging for the new `libjpeg-turbo` dependency: added to
+  `docs/BUILDING.md` (apt/brew/vcpkg) and the `.deb` control file's
+  `Depends:` (`libjpeg-turbo8`). The Windows Inno Setup script already
+  wildcards `*.dll` so no change was needed there, and macOS's
+  `macdeployqt`-based bundling picks up non-system dylibs automatically.
+  The Flatpak manifests (`packaging/flatpak/*.yml`) were left unchanged on
+  the assumption that `org.kde.Platform`/`Sdk` 6.11 already bundles
+  libjpeg-turbo (a standard Qt JPEG-plugin dependency) -- worth confirming
+  the next time a Flatpak build is actually run, since it wasn't
+  independently verified here
+- No dynamic resize (connects at the server's native resolution; the
+  `Scale to Fit`/`Actual Size` toggle changes how that fixed resolution is
+  displayed locally, not what resolution is requested from the guest --
+  VNC has no equivalent of RDP's MS-RDPEDISP for that)
 
 ## Milestone 7 - Cross-Platform Protocol Hardening
 
@@ -200,6 +348,9 @@ Git:
 - Release: [v2026.9.8](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.8) (`v2026.9.8` tag, installers for Windows/Linux/macOS)
 - Release: [v2026.9.8.2](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.8.2) — same-day patch fixing RDP TLS certificate verification (was fully disabled) and preparing Flatpak packaging for Flathub submission
 - Release: [v2026.9.8.3](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.8.3) — same-day patch adding an in-app User Guide and standalone User Guide PDF
+- Release: [v2026.9.14](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.14) — fixes distorted RDP text on HiDPI monitors and reduces RDP resize-related display glitches
+- Release: [v2026.9.14.2](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.14.2) — same-day patch fixing RDP display corruption (missing/misplaced taskbar) after resizing the session window (the client never resized its own display buffer for channel-driven RDP resizes)
+- Release: [v2026.9.15](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.15) — adds Import/Export for profile lists (File menu)
 
 ## Milestone 10 - v1.0 Stabilization
 

packaging/flatpak/flathub/org.darksingularity.OrbitHub.yml

@@ -19,5 +19,5 @@ modules:
     sources:
       - type: git
         url: https://git.darksingularity.org/DarkSingularity/orbithub.git
-        tag: v2026.9.8.2
+        tag: v2026.9.15
-        commit: 4c649f727fb794f4b5afdc3186e545e20ce2f138
+        commit: dffca3afef80b5a3ca4832e0b7f748775cb90328

packaging/linux/build-deb.sh

@@ -17,6 +17,11 @@ mkdir -p "$DIST_DIR"
 rm -rf "$STAGE_DIR"
 mkdir -p "$PKG_ROOT/DEBIAN"
 
+# Read VERSION only after the build (which reconfigures CMakeCache.txt if
+# CMakeLists.txt changed since the build dir was last configured) --
+# reading it beforehand risks packaging a stale version string.
+cmake --build "$BUILD_DIR" -j
+
 VERSION="$(sed -n 's/^CMAKE_PROJECT_VERSION:STATIC=//p' "$BUILD_DIR/CMakeCache.txt" | head -n1)"
 ARCH="$(dpkg --print-architecture)"
 
@@ -25,7 +30,6 @@ if [[ -z "$VERSION" ]]; then
   exit 1
 fi
 
-cmake --build "$BUILD_DIR" -j
 cmake --install "$BUILD_DIR" --prefix "$PKG_ROOT/usr"
 
 cat > "$PKG_ROOT/DEBIAN/control" <<EOF
@@ -35,7 +39,7 @@ Section: net
 Priority: optional
 Architecture: ${ARCH}
 Maintainer: OrbitHub Maintainers <maintainers@orbithub.local>
-Depends: libc6, libstdc++6, libqt6core6, libqt6gui6, libqt6widgets6, libqt6sql6, libssl3, zlib1g, openssh-client
+Depends: libc6, libstdc++6, libqt6core6, libqt6gui6, libqt6widgets6, libqt6sql6, libssl3, zlib1g, libjpeg-turbo8, openssh-client
 Description: OrbitHub remote session manager
  OrbitHub is a native desktop application for managing connection profiles
  and opening SSH and RDP sessions in a tabbed interface.

packaging/linux/org.darksingularity.OrbitHub.metainfo.xml

@@ -34,6 +34,24 @@
     </screenshot>
   </screenshots>
   <releases>
+    <release version="2026.9.15" date="2026-09-15">
+      <url>https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.15</url>
+      <description>
+        <p>Adds Import/Export for profile lists (File menu).</p>
+      </description>
+    </release>
+    <release version="2026.9.14.2" date="2026-09-14">
+      <url>https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.14.2</url>
+      <description>
+        <p>Fixes RDP display corruption (missing/misplaced taskbar, stale composited content) after resizing the session window.</p>
+      </description>
+    </release>
+    <release version="2026.9.14" date="2026-09-14">
+      <url>https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.14</url>
+      <description>
+        <p>Fixes distorted RDP text on HiDPI monitors, and reduces RDP resize-related display glitches.</p>
+      </description>
+    </release>
     <release version="2026.9.8.3" date="2026-09-08">
       <url>https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.8.3</url>
       <description>

packaging/macos/build-dmg.sh

@@ -14,12 +14,6 @@ if [[ ! -f "$BUILD_DIR/CMakeCache.txt" ]]; then
   exit 1
 fi
 
-VERSION="$(sed -n 's/^CMAKE_PROJECT_VERSION:STATIC=//p' "$BUILD_DIR/CMakeCache.txt" | head -n1)"
-if [[ -z "$VERSION" ]]; then
-  echo "Unable to determine project version from $BUILD_DIR/CMakeCache.txt" >&2
-  exit 1
-fi
-
 MACDEPLOYQT="$(brew --prefix qt@6)/bin/macdeployqt"
 if [[ ! -x "$MACDEPLOYQT" ]]; then
   echo "macdeployqt not found at $MACDEPLOYQT" >&2
@@ -31,7 +25,17 @@ mkdir -p "$DIST_DIR"
 rm -rf "$STAGE_DIR" "$INSTALL_PREFIX"
 mkdir -p "$STAGE_DIR"
 
+# Read VERSION only after the build (which reconfigures CMakeCache.txt if
+# CMakeLists.txt changed since the build dir was last configured) --
+# reading it beforehand risks packaging a stale version string.
 cmake --build "$BUILD_DIR" -j
+
+VERSION="$(sed -n 's/^CMAKE_PROJECT_VERSION:STATIC=//p' "$BUILD_DIR/CMakeCache.txt" | head -n1)"
+if [[ -z "$VERSION" ]]; then
+  echo "Unable to determine project version from $BUILD_DIR/CMakeCache.txt" >&2
+  exit 1
+fi
+
 cmake --install "$BUILD_DIR" --prefix "$INSTALL_PREFIX"
 
 if [[ ! -d "$INSTALL_PREFIX/$APP_BUNDLE" ]]; then

src/about_dialog.cpp

@@ -8,6 +8,31 @@
 #include <QTextBrowser>
 #include <QVBoxLayout>
 
+namespace {
+// palette(mid) is meant for 3D bevel/shadow decoration, not text — it has
+// poor contrast against the window background in dark themes (barely
+// legible). Blend the widget's actual text and window colors instead, so
+// the result is reliably readable — de-emphasized relative to full-strength
+// text, but never low-contrast — in either a light or dark theme.
+QColor mutedTextColor(const QWidget* widget)
+{
+    const QPalette pal = widget->palette();
+    const QColor text = pal.color(QPalette::WindowText);
+    const QColor background = pal.color(QPalette::Window);
+    constexpr qreal kTextWeight = 0.65;
+
+    auto blend = [kTextWeight](int textChannel, int backgroundChannel) {
+        return qBound(0,
+                      qRound(textChannel * kTextWeight + backgroundChannel * (1.0 - kTextWeight)),
+                      255);
+    };
+
+    return QColor(blend(text.red(), background.red()),
+                  blend(text.green(), background.green()),
+                  blend(text.blue(), background.blue()));
+}
+}
+
 AboutDialog::AboutDialog(QWidget* parent) : QDialog(parent)
 {
     setWindowTitle(QStringLiteral("About OrbitHub"));
@@ -34,7 +59,7 @@ AboutDialog::AboutDialog(QWidget* parent) : QDialog(parent)
         QStringLiteral("Unified remote session manager for SSH, RDP, and VNC workflows."),
         this);
     subtitle->setWordWrap(true);
-    subtitle->setStyleSheet(QStringLiteral("color: palette(mid);"));
+    subtitle->setStyleSheet(QStringLiteral("color: %1;").arg(mutedTextColor(this).name()));
 
     const QString version = QCoreApplication::applicationVersion().trimmed().isEmpty()
         ? QStringLiteral("Development build")
@@ -42,7 +67,7 @@ AboutDialog::AboutDialog(QWidget* parent) : QDialog(parent)
     auto* buildLine = new QLabel(
         QStringLiteral("Version: %1 | Qt runtime linked dynamically").arg(version),
         this);
-    buildLine->setStyleSheet(QStringLiteral("color: palette(mid);"));
+    buildLine->setStyleSheet(QStringLiteral("color: %1;").arg(mutedTextColor(this).name()));
 
     titleColumn->addWidget(title);
     titleColumn->addWidget(subtitle);

src/main.cpp

@@ -10,6 +10,9 @@ int main(int argc, char* argv[])
     QApplication app(argc, argv);
     app.setOrganizationName(QStringLiteral("FireBugIT"));
     app.setApplicationName(QStringLiteral("OrbitHub"));
+#ifdef ORBITHUB_VERSION_STRING
+    app.setApplicationVersion(QStringLiteral(ORBITHUB_VERSION_STRING));
+#endif
     app.setWindowIcon(createOrbitHubAppIcon());
 
     SessionWindow window;

src/mremoteng_importer.cpp

@@ -0,0 +1,152 @@
+#include "mremoteng_importer.h"
+
+#include <QStringList>
+#include <QXmlStreamReader>
+
+namespace {
+QString joinFolderPath(const QStringList& parts)
+{
+    QStringList trimmed;
+    for (const QString& part : parts) {
+        const QString t = part.trimmed();
+        if (!t.isEmpty()) {
+            trimmed.push_back(t);
+        }
+    }
+    return trimmed.join(QStringLiteral("/"));
+}
+
+// Maps mRemoteNG's Protocol attribute (an enum: RDP, VNC, SSH1, SSH2,
+// Telnet, Rlogin, RAW, HTTP, HTTPS, PowerShell, IntApp, Winbox) onto what
+// OrbitHub actually supports. *supported is set to false for anything
+// OrbitHub can't yet connect to (VNC included -- see issue #3).
+QString mappedProtocol(const QString& mRemoteNGProtocol, bool* supported)
+{
+    const QString p = mRemoteNGProtocol.trimmed();
+    if (p.compare(QStringLiteral("RDP"), Qt::CaseInsensitive) == 0) {
+        *supported = true;
+        return QStringLiteral("RDP");
+    }
+    if (p.compare(QStringLiteral("SSH1"), Qt::CaseInsensitive) == 0
+        || p.compare(QStringLiteral("SSH2"), Qt::CaseInsensitive) == 0) {
+        *supported = true;
+        return QStringLiteral("SSH");
+    }
+    *supported = false;
+    return p;
+}
+
+int defaultPortFor(const QString& orbitHubProtocol)
+{
+    return orbitHubProtocol == QStringLiteral("RDP") ? 3389 : 22;
+}
+}
+
+MRemoteNGImportResult parseMRemoteNGConnections(const QByteArray& xmlData)
+{
+    MRemoteNGImportResult result;
+
+    QXmlStreamReader reader(xmlData);
+
+    bool foundRoot = false;
+    while (!reader.atEnd() && !foundRoot) {
+        if (reader.readNext() == QXmlStreamReader::StartElement) {
+            if (reader.name().compare(QStringLiteral("Connections"), Qt::CaseInsensitive) != 0) {
+                result.errorMessage = QStringLiteral(
+                    "This doesn't look like an mRemoteNG connections file (expected a "
+                    "<Connections> root element).");
+                return result;
+            }
+            foundRoot = true;
+
+            const auto attrs = reader.attributes();
+            if (attrs.value(QStringLiteral("FullFileEncryption"))
+                    .compare(QStringLiteral("true"), Qt::CaseInsensitive)
+                == 0) {
+                result.errorMessage = QStringLiteral(
+                    "This file has \"full file encryption\" enabled in mRemoteNG, which "
+                    "encrypts the entire connection list with your master password. "
+                    "OrbitHub has no way to read that. In mRemoteNG, re-export with full "
+                    "file encryption turned off (only the saved passwords need stay "
+                    "encrypted -- OrbitHub never imports those anyway).");
+                return result;
+            }
+        }
+    }
+
+    if (!foundRoot) {
+        result.errorMessage = QStringLiteral("Not a valid XML file, or the file is empty.");
+        return result;
+    }
+
+    QStringList folderStack;
+    std::vector<bool> openNodeIsContainer;
+
+    while (!reader.atEnd()) {
+        const QXmlStreamReader::TokenType token = reader.readNext();
+
+        if (token == QXmlStreamReader::StartElement
+            && reader.name().compare(QStringLiteral("Node"), Qt::CaseInsensitive) == 0) {
+            const auto attrs = reader.attributes();
+            const QString type = attrs.value(QStringLiteral("Type")).toString();
+            const bool isContainer =
+                type.compare(QStringLiteral("Container"), Qt::CaseInsensitive) == 0;
+            const QString name = attrs.value(QStringLiteral("Name")).toString().trimmed();
+
+            if (isContainer) {
+                folderStack.push_back(name);
+                const QString path = joinFolderPath(folderStack);
+                if (!path.isEmpty()) {
+                    result.folders.push_back(path);
+                }
+            } else {
+                bool supported = false;
+                const QString protocolLabel = attrs.value(QStringLiteral("Protocol")).toString();
+                const QString mappedProto = mappedProtocol(protocolLabel, &supported);
+
+                if (!supported) {
+                    result.skippedUnsupportedProtocol.push_back(QStringLiteral("%1 (%2)").arg(
+                        name.isEmpty() ? QStringLiteral("(unnamed)") : name,
+                        protocolLabel.isEmpty() ? QStringLiteral("unknown") : protocolLabel));
+                } else {
+                    MRemoteNGImportedProfile imported;
+                    imported.profile.name = name;
+                    imported.profile.host = attrs.value(QStringLiteral("Hostname")).toString().trimmed();
+                    const QString portText = attrs.value(QStringLiteral("Port")).toString();
+                    imported.profile.port =
+                        portText.isEmpty() ? defaultPortFor(mappedProto) : portText.toInt();
+                    if (imported.profile.port <= 0) {
+                        imported.profile.port = defaultPortFor(mappedProto);
+                    }
+                    imported.profile.username = attrs.value(QStringLiteral("Username")).toString();
+                    imported.profile.protocol = mappedProto;
+                    imported.profile.authMode = QStringLiteral("Password");
+                    if (mappedProto == QStringLiteral("RDP")) {
+                        imported.profile.domain = attrs.value(QStringLiteral("Domain")).toString();
+                    }
+                    imported.folderPath = joinFolderPath(folderStack);
+                    result.profiles.push_back(imported);
+                }
+            }
+
+            openNodeIsContainer.push_back(isContainer);
+        } else if (token == QXmlStreamReader::EndElement
+                   && reader.name().compare(QStringLiteral("Node"), Qt::CaseInsensitive) == 0) {
+            if (!openNodeIsContainer.empty()) {
+                if (openNodeIsContainer.back()) {
+                    folderStack.removeLast();
+                }
+                openNodeIsContainer.pop_back();
+            }
+        }
+    }
+
+    if (reader.hasError()) {
+        result.errorMessage = QStringLiteral("Failed to parse XML: %1").arg(reader.errorString());
+        result.folders.clear();
+        result.profiles.clear();
+        result.skippedUnsupportedProtocol.clear();
+    }
+
+    return result;
+}

src/mremoteng_importer.h

@@ -0,0 +1,48 @@
+#ifndef ORBITHUB_MREMOTENG_IMPORTER_H
+#define ORBITHUB_MREMOTENG_IMPORTER_H
+
+#include "profile_repository.h"
+
+#include <QByteArray>
+#include <QString>
+#include <QStringList>
+
+#include <vector>
+
+// A profile parsed out of an mRemoteNG confCons.xml export, plus which
+// folder (if any) it belongs to, expressed the same way ProfilesWindow's
+// own folder paths are ("Parent/Child").
+struct MRemoteNGImportedProfile
+{
+    Profile profile;
+    QString folderPath;
+};
+
+struct MRemoteNGImportResult
+{
+    // Non-empty only when parsing failed outright (malformed XML, or a
+    // FullFileEncryption="true" export -- that encrypts the whole node
+    // tree with the user's master password, which OrbitHub has no way to
+    // ask for or use, so those files can't be read at all here).
+    QString errorMessage;
+
+    // Every folder path that appeared, including ones with no directly
+    // imported profile in them (e.g. a container that held only
+    // unsupported-protocol connections).
+    std::vector<QString> folders;
+
+    std::vector<MRemoteNGImportedProfile> profiles;
+
+    // "<name> (<mRemoteNG protocol>)" for each connection whose protocol
+    // OrbitHub doesn't support (VNC, Telnet, HTTP, ...) -- skipped, never
+    // silently dropped.
+    QStringList skippedUnsupportedProtocol;
+};
+
+// Passwords are never read from the file, even for the common case where
+// they're readable without a master password (mRemoteNG only encrypts the
+// Password attribute itself, not the surrounding plaintext fields) --
+// OrbitHub never persists credentials on a Profile in the first place.
+MRemoteNGImportResult parseMRemoteNGConnections(const QByteArray& xmlData);
+
+#endif

src/profile_dialog.cpp

@@ -257,13 +257,6 @@ void ProfileDialog::accept()
     }
 
     const QString protocol = m_protocolInput->currentText();
-    if ((protocol == QStringLiteral("SSH") || protocol == QStringLiteral("RDP"))
-        && m_usernameInput->text().trimmed().isEmpty()) {
-        QMessageBox::warning(this,
-                             QStringLiteral("Validation Error"),
-                             QStringLiteral("Username is required for %1 profiles.").arg(protocol));
-        return;
-    }
 
     if (protocol == QStringLiteral("SSH")
         && m_authModeInput->currentText() == QStringLiteral("Private Key")) {
@@ -310,16 +303,20 @@ void ProfileDialog::refreshAuthFields()
 
     if (isSsh) {
         m_usernameInput->setPlaceholderText(QStringLiteral("deploy"));
-        m_protocolHint->setText(
+        m_protocolHint->setText(QStringLiteral(
-            QStringLiteral("SSH: username is required. Choose Password or Private Key auth."));
+            "SSH: you'll be asked for a username at connect time if left blank here. "
+            "Choose Password or Private Key auth."));
     } else if (isRdp) {
         m_usernameInput->setPlaceholderText(QStringLiteral("Administrator"));
-        m_protocolHint->setText(
+        m_protocolHint->setText(QStringLiteral(
-            QStringLiteral("RDP: username and password are required. Domain is optional."));
+            "RDP: you'll be asked for a username at connect time if left blank here. "
+            "Domain is optional."));
     } else if (isVnc) {
         m_usernameInput->setPlaceholderText(QStringLiteral("optional"));
-        m_protocolHint->setText(
+        m_protocolHint->setText(QStringLiteral(
-            QStringLiteral("VNC: host and port are required. Username/domain are optional and ignored by most servers."));
+            "VNC: host and port are required. Username is optional and ignored by most "
+            "servers, except macOS's built-in Screen Sharing, which requires it. Domain is "
+            "unused."));
     }
 
     m_folderHint->setText(m_defaultFolderPath.isEmpty()

src/profile_repository.cpp

@@ -9,7 +9,11 @@
 #include <QVariant>
 #include <QStringList>
 
+#include <atomic>
+
 namespace {
+std::atomic<int> g_testConnectionCounter{0};
+
 QString buildDatabasePath()
 {
     QString appDataPath = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);
@@ -176,7 +180,7 @@ void bindProfileFields(QSqlQuery& query, const Profile& profile)
                              : QStringLiteral("Negotiate"));
     query.addBindValue(isRdp ? normalizedRdpPerformanceProfile(profile.rdpPerformanceProfile)
                              : QStringLiteral("Balanced"));
-    query.addBindValue(normalizedTags(profile.tags));
+    query.addBindValue(nonNullTrimmed(normalizedTags(profile.tags)));
 }
 
 Profile profileFromQuery(const QSqlQuery& query)
@@ -259,6 +263,16 @@ ProfileRepository::ProfileRepository() : m_connectionName(QStringLiteral("orbith
     }
 }
 
+ProfileRepository::ProfileRepository(const QString& databasePathOverride)
+    : m_connectionName(QStringLiteral("orbithub_test_%1")
+                            .arg(g_testConnectionCounter.fetch_add(1))),
+      m_databasePathOverride(databasePathOverride)
+{
+    if (!initializeDatabase()) {
+        QSqlDatabase::removeDatabase(m_connectionName);
+    }
+}
+
 ProfileRepository::~ProfileRepository()
 {
     if (QSqlDatabase::contains(m_connectionName)) {
@@ -332,6 +346,123 @@ bool ProfileRepository::createFolder(const QString& folderPath) const
     return true;
 }
 
+// Deleting a folder never destroys profiles: everything directly inside it
+// (profiles and subfolders alike) is shifted up to take the deleted
+// folder's place, exactly as if that one path segment had been removed
+// from each of their paths. This is the least-surprising behavior for what
+// is fundamentally just an organizational label, not a container that owns
+// its contents.
+bool ProfileRepository::deleteFolder(const QString& folderPath) const
+{
+    if (!QSqlDatabase::contains(m_connectionName)) {
+        return false;
+    }
+
+    const QString normalized = normalizedFolderPath(folderPath);
+    if (normalized.isEmpty()) {
+        setLastError(QStringLiteral("Folder path is required."));
+        return false;
+    }
+
+    setLastError(QString());
+
+    QString parentPath;
+    const int lastSlash = normalized.lastIndexOf(QChar::fromLatin1('/'));
+    if (lastSlash >= 0) {
+        parentPath = normalized.left(lastSlash);
+    }
+
+    const QString prefix = normalized + QStringLiteral("/");
+    auto remap = [&](const QString& oldPath) {
+        if (oldPath == normalized) {
+            return nonNullTrimmed(parentPath);
+        }
+        const QString remainder = oldPath.mid(prefix.length());
+        return nonNullTrimmed(parentPath.isEmpty() ? remainder
+                                                    : parentPath + QStringLiteral("/") + remainder);
+    };
+
+    QSqlDatabase database = QSqlDatabase::database(m_connectionName);
+    if (!database.transaction()) {
+        setLastError(database.lastError().text());
+        return false;
+    }
+
+    // Reassign affected profiles. Matching is done in C++ (not SQL LIKE)
+    // so a folder name containing '%' or '_' can't be misinterpreted as a
+    // wildcard.
+    QSqlQuery selectProfiles(database);
+    if (!selectProfiles.exec(QStringLiteral("SELECT id, folder_path FROM profiles"))) {
+        setLastError(selectProfiles.lastError().text());
+        database.rollback();
+        return false;
+    }
+    std::vector<std::pair<qint64, QString>> profileUpdates;
+    while (selectProfiles.next()) {
+        const QString path = normalizedFolderPath(selectProfiles.value(1).toString());
+        if (path == normalized || path.startsWith(prefix)) {
+            profileUpdates.emplace_back(selectProfiles.value(0).toLongLong(), remap(path));
+        }
+    }
+    for (const auto& [id, newPath] : profileUpdates) {
+        QSqlQuery update(database);
+        update.prepare(QStringLiteral("UPDATE profiles SET folder_path = ? WHERE id = ?"));
+        update.addBindValue(newPath);
+        update.addBindValue(id);
+        if (!update.exec()) {
+            setLastError(update.lastError().text());
+            database.rollback();
+            return false;
+        }
+    }
+
+    // Reassign (or drop, for the folder itself) affected explicit folder
+    // markers the same way.
+    QSqlQuery selectFolders(database);
+    if (!selectFolders.exec(QStringLiteral("SELECT path FROM profile_folders"))) {
+        setLastError(selectFolders.lastError().text());
+        database.rollback();
+        return false;
+    }
+    QStringList affectedFolders;
+    while (selectFolders.next()) {
+        const QString path = normalizedFolderPath(selectFolders.value(0).toString());
+        if (path == normalized || path.startsWith(prefix)) {
+            affectedFolders.push_back(path);
+        }
+    }
+    for (const QString& oldPath : affectedFolders) {
+        QSqlQuery remove(database);
+        remove.prepare(QStringLiteral("DELETE FROM profile_folders WHERE path = ?"));
+        remove.addBindValue(oldPath);
+        if (!remove.exec()) {
+            setLastError(remove.lastError().text());
+            database.rollback();
+            return false;
+        }
+
+        const QString newPath = remap(oldPath);
+        if (oldPath != normalized && !newPath.isEmpty()) {
+            QSqlQuery insert(database);
+            insert.prepare(QStringLiteral("INSERT OR IGNORE INTO profile_folders(path) VALUES (?)"));
+            insert.addBindValue(newPath);
+            if (!insert.exec()) {
+                setLastError(insert.lastError().text());
+                database.rollback();
+                return false;
+            }
+        }
+    }
+
+    if (!database.commit()) {
+        setLastError(database.lastError().text());
+        database.rollback();
+        return false;
+    }
+
+    return true;
+}
+
 std::vector<Profile> ProfileRepository::listProfiles(const QString& searchQuery,
                                                      ProfileSortOrder sortOrder) const
 {
@@ -485,7 +616,8 @@ bool ProfileRepository::deleteProfile(qint64 id) const
 bool ProfileRepository::initializeDatabase()
 {
     QSqlDatabase database = QSqlDatabase::addDatabase(QStringLiteral("QSQLITE"), m_connectionName);
-    database.setDatabaseName(buildDatabasePath());
+    database.setDatabaseName(
+        m_databasePathOverride.isEmpty() ? buildDatabasePath() : m_databasePathOverride);
 
     if (!database.open()) {
         m_initError = database.lastError().text();

src/profile_repository.h

@@ -35,6 +35,9 @@ class ProfileRepository
 {
 public:
     ProfileRepository();
+    // databasePathOverride lets tests point the repository at an isolated,
+    // disposable SQLite file instead of the real app-data location.
+    explicit ProfileRepository(const QString& databasePathOverride);
     ~ProfileRepository();
 
     QString initError() const;
@@ -44,6 +47,7 @@ public:
                                       ProfileSortOrder sortOrder = ProfileSortOrder::NameAsc) const;
     std::vector<QString> listFolders() const;
     bool createFolder(const QString& folderPath) const;
+    bool deleteFolder(const QString& folderPath) const;
     std::optional<Profile> getProfile(qint64 id) const;
     std::optional<Profile> createProfile(const Profile& profile) const;
     bool updateProfile(const Profile& profile) const;
@@ -51,6 +55,7 @@ public:
 
 private:
     QString m_connectionName;
+    QString m_databasePathOverride;
     QString m_initError;
     mutable QString m_lastError;
 

src/profiles_window.cpp

@@ -1,5 +1,6 @@
 #include "profiles_window.h"
 
+#include "mremoteng_importer.h"
 #include "profile_dialog.h"
 #include "profile_repository.h"
 #include "profiles_tree_widget.h"
@@ -7,8 +8,13 @@
 #include <QAction>
 #include <QAbstractItemView>
 #include <QComboBox>
+#include <QFile>
+#include <QFileDialog>
 #include <QHeaderView>
 #include <QHBoxLayout>
+#include <QJsonArray>
+#include <QJsonDocument>
+#include <QJsonObject>
 #include <QLabel>
 #include <QLineEdit>
 #include <QInputDialog>
@@ -85,6 +91,53 @@ bool profileHasTag(const Profile& profile, const QString& requestedTag)
 
     return false;
 }
+
+constexpr int kProfileExportFormatVersion = 1;
+
+QJsonObject profileToJson(const Profile& profile)
+{
+    QJsonObject object;
+    object.insert(QStringLiteral("name"), profile.name);
+    object.insert(QStringLiteral("host"), profile.host);
+    object.insert(QStringLiteral("port"), profile.port);
+    object.insert(QStringLiteral("username"), profile.username);
+    object.insert(QStringLiteral("domain"), profile.domain);
+    object.insert(QStringLiteral("folderPath"), profile.folderPath);
+    object.insert(QStringLiteral("protocol"), profile.protocol);
+    object.insert(QStringLiteral("authMode"), profile.authMode);
+    object.insert(QStringLiteral("privateKeyPath"), profile.privateKeyPath);
+    object.insert(QStringLiteral("knownHostsPolicy"), profile.knownHostsPolicy);
+    object.insert(QStringLiteral("rdpSecurityMode"), profile.rdpSecurityMode);
+    object.insert(QStringLiteral("rdpPerformanceProfile"), profile.rdpPerformanceProfile);
+    object.insert(QStringLiteral("tags"), profile.tags);
+    return object;
+}
+
+// Deliberately excludes id (import always creates new rows -- an imported
+// profile's id has no meaning in the destination database) and any
+// credential material (none is ever persisted on Profile in the first
+// place, see ProfileRepository).
+Profile profileFromJson(const QJsonObject& object)
+{
+    Profile profile;
+    profile.name = object.value(QStringLiteral("name")).toString();
+    profile.host = object.value(QStringLiteral("host")).toString();
+    profile.port = object.value(QStringLiteral("port")).toInt(22);
+    profile.username = object.value(QStringLiteral("username")).toString();
+    profile.domain = object.value(QStringLiteral("domain")).toString();
+    profile.folderPath = object.value(QStringLiteral("folderPath")).toString();
+    profile.protocol = object.value(QStringLiteral("protocol")).toString(QStringLiteral("SSH"));
+    profile.authMode = object.value(QStringLiteral("authMode")).toString(QStringLiteral("Password"));
+    profile.privateKeyPath = object.value(QStringLiteral("privateKeyPath")).toString();
+    profile.knownHostsPolicy =
+        object.value(QStringLiteral("knownHostsPolicy")).toString(QStringLiteral("Ask"));
+    profile.rdpSecurityMode =
+        object.value(QStringLiteral("rdpSecurityMode")).toString(QStringLiteral("Negotiate"));
+    profile.rdpPerformanceProfile =
+        object.value(QStringLiteral("rdpPerformanceProfile")).toString(QStringLiteral("Balanced"));
+    profile.tags = object.value(QStringLiteral("tags")).toString();
+    return profile;
+}
 }
 
 ProfilesWindow::ProfilesWindow(QWidget* parent)
@@ -535,6 +588,8 @@ void ProfilesWindow::showTreeContextMenu(const QPoint& pos)
 
     const QString contextFolder = folderPathForItem(item);
     const bool isProfileItem = item != nullptr && item->data(0, kProfileIdRole).isValid();
+    const bool isFolderItem =
+        item != nullptr && !isProfileItem && item->data(0, kFolderPathRole).isValid();
 
     QMenu menu(this);
     QAction* newConnectionAction = menu.addAction(QStringLiteral("New Connection"));
@@ -542,12 +597,16 @@ void ProfilesWindow::showTreeContextMenu(const QPoint& pos)
     QAction* connectAction = nullptr;
     QAction* editAction = nullptr;
     QAction* deleteAction = nullptr;
+    QAction* deleteFolderAction = nullptr;
 
     if (isProfileItem) {
         menu.addSeparator();
         connectAction = menu.addAction(QStringLiteral("Connect"));
         editAction = menu.addAction(QStringLiteral("Edit"));
         deleteAction = menu.addAction(QStringLiteral("Delete"));
+    } else if (isFolderItem) {
+        menu.addSeparator();
+        deleteFolderAction = menu.addAction(QStringLiteral("Delete Folder"));
     }
 
     QAction* chosen = menu.exec(m_profilesTree->viewport()->mapToGlobal(pos));
@@ -577,6 +636,10 @@ void ProfilesWindow::showTreeContextMenu(const QPoint& pos)
         deleteSelectedProfile();
         return;
     }
+    if (isFolderItem && chosen == deleteFolderAction) {
+        deleteFolderInContext(contextFolder);
+        return;
+    }
 }
 
 void ProfilesWindow::createFolderInContext(const QString& baseFolderPath)
@@ -614,6 +677,72 @@ void ProfilesWindow::createFolderInContext(const QString& baseFolderPath)
     loadProfiles();
 }
 
+void ProfilesWindow::deleteFolderInContext(const QString& folderPath)
+{
+    const QString normalized = normalizeFolderPathForView(folderPath);
+    if (normalized.isEmpty()) {
+        return;
+    }
+
+    // Deleting a folder never deletes profiles -- everything inside it
+    // (profiles and subfolders) shifts up to take its place. Count what's
+    // affected so the confirmation is honest about that, rather than
+    // reading like the usual destructive "Delete" action.
+    const QString prefix = normalized + QStringLiteral("/");
+    int profileCount = 0;
+    for (const Profile& profile : m_repository->listProfiles()) {
+        if (profile.folderPath == normalized || profile.folderPath.startsWith(prefix)) {
+            ++profileCount;
+        }
+    }
+    int subfolderCount = 0;
+    for (const QString& folder : m_repository->listFolders()) {
+        if (folder != normalized && folder.startsWith(prefix)) {
+            ++subfolderCount;
+        }
+    }
+
+    if (profileCount > 0 || subfolderCount > 0) {
+        QStringList parentParts = splitFolderPath(normalized);
+        parentParts.removeLast();
+        const QString destination = parentParts.isEmpty()
+            ? QStringLiteral("the top level")
+            : QStringLiteral("'%1'").arg(parentParts.join(QStringLiteral("/")));
+
+        QStringList details;
+        if (profileCount > 0) {
+            details.push_back(QStringLiteral("%1 profile(s)").arg(profileCount));
+        }
+        if (subfolderCount > 0) {
+            details.push_back(QStringLiteral("%1 subfolder(s)").arg(subfolderCount));
+        }
+
+        const QMessageBox::StandardButton confirm = QMessageBox::question(
+            this,
+            QStringLiteral("Delete Folder"),
+            QStringLiteral("Delete folder '%1'?\n\nNothing will be deleted: %2 currently inside "
+                           "it will move up to %3.")
+                .arg(normalized, details.join(QStringLiteral(" and ")), destination),
+            QMessageBox::Yes | QMessageBox::No,
+            QMessageBox::No);
+        if (confirm != QMessageBox::Yes) {
+            return;
+        }
+    }
+
+    if (!m_repository->deleteFolder(normalized)) {
+        QMessageBox::warning(this,
+                             QStringLiteral("Delete Folder"),
+                             QStringLiteral("Failed to delete folder: %1")
+                                 .arg(m_repository->lastError().isEmpty()
+                                          ? QStringLiteral("unknown error")
+                                          : m_repository->lastError()));
+        return;
+    }
+
+    loadProfiles();
+}
+
 void ProfilesWindow::persistFolderAssignmentsFromTree()
 {
     if (!isFolderViewEnabled() || m_profilesTree == nullptr) {
@@ -930,3 +1059,197 @@ void ProfilesWindow::createFolderInCurrentContext()
     const QString folderPath = folderPathForItem(m_profilesTree->currentItem());
     createFolderInContext(folderPath);
 }
+
+void ProfilesWindow::exportProfiles()
+{
+    const QString fileName = QFileDialog::getSaveFileName(
+        this, QStringLiteral("Export Profiles"), QStringLiteral("orbithub-profiles.json"),
+        QStringLiteral("JSON Files (*.json)"));
+    if (fileName.isEmpty()) {
+        return;
+    }
+
+    QJsonArray folders;
+    for (const QString& folderPath : m_repository->listFolders()) {
+        folders.append(folderPath);
+    }
+
+    QJsonArray profiles;
+    for (const Profile& profile : m_repository->listProfiles()) {
+        profiles.append(profileToJson(profile));
+    }
+
+    QJsonObject root;
+    root.insert(QStringLiteral("orbithubProfileExport"), kProfileExportFormatVersion);
+    root.insert(QStringLiteral("folders"), folders);
+    root.insert(QStringLiteral("profiles"), profiles);
+
+    QFile file(fileName);
+    if (!file.open(QIODevice::WriteOnly | QIODevice::Truncate)) {
+        QMessageBox::warning(this,
+                             QStringLiteral("Export Profiles"),
+                             QStringLiteral("Failed to write %1: %2")
+                                 .arg(fileName, file.errorString()));
+        return;
+    }
+    file.write(QJsonDocument(root).toJson(QJsonDocument::Indented));
+    file.close();
+
+    QMessageBox::information(this,
+                             QStringLiteral("Export Profiles"),
+                             QStringLiteral("Exported %1 profile(s) to %2.")
+                                 .arg(profiles.size())
+                                 .arg(fileName));
+}
+
+void ProfilesWindow::importProfiles()
+{
+    const QString fileName = QFileDialog::getOpenFileName(
+        this, QStringLiteral("Import Profiles"), QString(), QStringLiteral("JSON Files (*.json)"));
+    if (fileName.isEmpty()) {
+        return;
+    }
+
+    QFile file(fileName);
+    if (!file.open(QIODevice::ReadOnly)) {
+        QMessageBox::warning(this,
+                             QStringLiteral("Import Profiles"),
+                             QStringLiteral("Failed to read %1: %2")
+                                 .arg(fileName, file.errorString()));
+        return;
+    }
+
+    QJsonParseError parseError{};
+    const QJsonDocument doc = QJsonDocument::fromJson(file.readAll(), &parseError);
+    file.close();
+    if (parseError.error != QJsonParseError::NoError || !doc.isObject()) {
+        QMessageBox::warning(this,
+                             QStringLiteral("Import Profiles"),
+                             QStringLiteral("%1 is not a valid OrbitHub profile export: %2")
+                                 .arg(fileName, parseError.errorString()));
+        return;
+    }
+
+    const QJsonObject root = doc.object();
+    if (!root.value(QStringLiteral("profiles")).isArray()) {
+        QMessageBox::warning(this,
+                             QStringLiteral("Import Profiles"),
+                             QStringLiteral("%1 does not contain a profile list.").arg(fileName));
+        return;
+    }
+
+    for (const QJsonValue& folderValue : root.value(QStringLiteral("folders")).toArray()) {
+        const QString folderPath = folderValue.toString();
+        if (!folderPath.isEmpty()) {
+            m_repository->createFolder(folderPath);
+        }
+    }
+
+    const QJsonArray profilesArray = root.value(QStringLiteral("profiles")).toArray();
+    int imported = 0;
+    QStringList failures;
+    for (const QJsonValue& profileValue : profilesArray) {
+        if (!profileValue.isObject()) {
+            continue;
+        }
+        const Profile profile = profileFromJson(profileValue.toObject());
+        if (profile.name.isEmpty() || profile.host.isEmpty()) {
+            failures.push_back(QStringLiteral("(unnamed profile): missing name or host"));
+            continue;
+        }
+        // No need to createFolder(profile.folderPath) here: the tree view
+        // already synthesizes folder nodes from a profile's own folderPath
+        // (see ProfilesWindow::loadProfiles). Explicit profile_folders rows
+        // are only for folders with no profiles in them, and those are
+        // already recreated above from the export's top-level "folders"
+        // list -- doing it again per-profile would just add spurious
+        // entries not present in the original export.
+        if (m_repository->createProfile(profile).has_value()) {
+            ++imported;
+        } else {
+            failures.push_back(QStringLiteral("%1: %2").arg(profile.name, m_repository->lastError()));
+        }
+    }
+
+    loadProfiles();
+
+    QString summary = QStringLiteral("Imported %1 of %2 profile(s) from %3.")
+                          .arg(imported)
+                          .arg(profilesArray.size())
+                          .arg(fileName);
+    if (!failures.isEmpty()) {
+        summary += QStringLiteral("\n\nFailed:\n%1").arg(failures.join(QChar::fromLatin1('\n')));
+        QMessageBox::warning(this, QStringLiteral("Import Profiles"), summary);
+    } else {
+        QMessageBox::information(this, QStringLiteral("Import Profiles"), summary);
+    }
+}
+
+void ProfilesWindow::importFromMRemoteNG()
+{
+    const QString fileName = QFileDialog::getOpenFileName(
+        this, QStringLiteral("Import from mRemoteNG"), QString(),
+        QStringLiteral("mRemoteNG Connections (*.xml)"));
+    if (fileName.isEmpty()) {
+        return;
+    }
+
+    QFile file(fileName);
+    if (!file.open(QIODevice::ReadOnly)) {
+        QMessageBox::warning(this,
+                             QStringLiteral("Import from mRemoteNG"),
+                             QStringLiteral("Failed to read %1: %2")
+                                 .arg(fileName, file.errorString()));
+        return;
+    }
+    const QByteArray xmlData = file.readAll();
+    file.close();
+
+    const MRemoteNGImportResult parsed = parseMRemoteNGConnections(xmlData);
+    if (!parsed.errorMessage.isEmpty()) {
+        QMessageBox::warning(this, QStringLiteral("Import from mRemoteNG"), parsed.errorMessage);
+        return;
+    }
+
+    for (const QString& folderPath : parsed.folders) {
+        m_repository->createFolder(folderPath);
+    }
+
+    int imported = 0;
+    QStringList failures;
+    for (const MRemoteNGImportedProfile& item : parsed.profiles) {
+        Profile profile = item.profile;
+        profile.folderPath = item.folderPath;
+        if (profile.name.isEmpty() || profile.host.isEmpty()) {
+            failures.push_back(QStringLiteral("(unnamed connection): missing name or host"));
+            continue;
+        }
+        if (m_repository->createProfile(profile).has_value()) {
+            ++imported;
+        } else {
+            failures.push_back(QStringLiteral("%1: %2").arg(profile.name, m_repository->lastError()));
+        }
+    }
+
+    loadProfiles();
+
+    QString summary = QStringLiteral("Imported %1 of %2 connection(s) from %3.\n\n"
+                                     "Passwords are never imported -- you'll be prompted the "
+                                     "first time you connect each profile, same as a new one.")
+                          .arg(imported)
+                          .arg(static_cast<int>(parsed.profiles.size()))
+                          .arg(fileName);
+    if (!parsed.skippedUnsupportedProtocol.isEmpty()) {
+        summary += QStringLiteral(
+                       "\n\nSkipped %1 connection(s) using a protocol OrbitHub doesn't support "
+                       "yet:\n%2")
+                       .arg(static_cast<int>(parsed.skippedUnsupportedProtocol.size()))
+                       .arg(parsed.skippedUnsupportedProtocol.join(QChar::fromLatin1('\n')));
+    }
+    if (!failures.isEmpty()) {
+        summary += QStringLiteral("\n\nFailed:\n%1").arg(failures.join(QChar::fromLatin1('\n')));
+        QMessageBox::warning(this, QStringLiteral("Import from mRemoteNG"), summary);
+    } else {
+        QMessageBox::information(this, QStringLiteral("Import from mRemoteNG"), summary);
+    }
+}

src/profiles_window.h

@@ -32,6 +32,9 @@ public:
 
     void createProfileInCurrentContext();
     void createFolderInCurrentContext();
+    void exportProfiles();
+    void importProfiles();
+    void importFromMRemoteNG();
 
 signals:
     void connectRequested(const Profile& profile);
@@ -63,6 +66,7 @@ private:
     QString folderPathForItem(const QTreeWidgetItem* item) const;
     void showTreeContextMenu(const QPoint& pos);
     void createFolderInContext(const QString& baseFolderPath);
+    void deleteFolderInContext(const QString& folderPath);
     void persistFolderAssignmentsFromTree();
     void collectProfileAssignments(const QTreeWidgetItem* item,
                                    const QString& parentFolderPath,

src/rdp_display_widget.cpp

@@ -1,6 +1,7 @@
 #include "rdp_display_widget.h"
 
 #include <QCursor>
+#include <QEvent>
 #include <QKeyEvent>
 #include <QMouseEvent>
 #include <QPainter>
@@ -15,20 +16,38 @@ QSize sanitizeSize(const QSize& size)
 {
     return QSize(qMax(1, size.width()), qMax(1, size.height()));
 }
+
+qreal sanitizeDevicePixelRatio(qreal ratio)
+{
+    if (!(ratio > 0.0)) {
+        return 1.0;
+    }
+    return qBound(1.0, ratio, 4.0);
+}
+
+// Windows' virtual-display driver can visibly glitch (stale composited
+// content left on screen) when asked to change resolution repeatedly in
+// quick succession, which naturally happens as the window's layout settles
+// right after creation/connect. Coalescing bursts of resize events into one
+// request avoids triggering that.
+constexpr int kResizeDebounceMs = 150;
 }
 
 RdpDisplayWidget::RdpDisplayWidget(QWidget* parent)
-    : QWidget(parent), m_remoteSize(1280, 720), m_cursorMode(CursorMode::Default)
+    : QWidget(parent),
+      m_remoteSize(1280, 720),
+      m_cursorMode(CursorMode::Default),
+      m_resizeDebounceTimer(new QTimer(this))
 {
     setFocusPolicy(Qt::StrongFocus);
     setMouseTracking(true);
     setAutoFillBackground(false);
     setMinimumSize(320, 200);
 
-    QTimer::singleShot(0, this, [this]() {
+    m_resizeDebounceTimer->setSingleShot(true);
-        const QSize size = sanitizeSize(this->size());
+    connect(m_resizeDebounceTimer, &QTimer::timeout, this, &RdpDisplayWidget::emitViewportGeometry);
-        emit viewportSizeChanged(size.width(), size.height());
+
-    });
+    scheduleViewportGeometryEmit();
 }
 
 void RdpDisplayWidget::setFrame(const QImage& frame)
@@ -54,6 +73,13 @@ void RdpDisplayWidget::setRemoteDesktopSize(int width, int height)
     }
 
     m_remoteSize = nextSize;
+    // The next actual frame (via setFrame) arrives asynchronously and isn't
+    // guaranteed to be sized to match yet. Drawing the old frame stretched
+    // to a renderRect() computed from the new m_remoteSize would scale it
+    // by the wrong factor for the transition window, producing visibly
+    // distorted/duplicated-looking content. Clear it and show the existing
+    // "waiting for frame" placeholder until a correctly-sized frame lands.
+    m_frame = QImage();
     update();
 }
 
@@ -140,11 +166,39 @@ void RdpDisplayWidget::paintEvent(QPaintEvent* event)
 void RdpDisplayWidget::resizeEvent(QResizeEvent* event)
 {
     QWidget::resizeEvent(event);
-    const QSize size = sanitizeSize(event->size());
+    scheduleViewportGeometryEmit();
-    emit viewportSizeChanged(size.width(), size.height());
     applyCursor();
 }
 
+bool RdpDisplayWidget::event(QEvent* event)
+{
+    // Fires when this widget's effective screen changes (e.g. dragged to a
+    // different monitor), which is what changes devicePixelRatio(). Newer
+    // Qt versions add a more specific QEvent::DevicePixelRatioChange, but
+    // this project's Qt 6.2 floor doesn't have it.
+    if (event->type() == QEvent::ScreenChangeInternal) {
+        scheduleViewportGeometryEmit();
+    }
+    return QWidget::event(event);
+}
+
+void RdpDisplayWidget::scheduleViewportGeometryEmit()
+{
+    // Restarting an already-running single-shot timer resets its countdown,
+    // so a burst of resize events collapses into one emission after things
+    // settle, rather than one request per event.
+    m_resizeDebounceTimer->start(kResizeDebounceMs);
+}
+
+void RdpDisplayWidget::emitViewportGeometry()
+{
+    const QSize logicalSize = sanitizeSize(this->size());
+    const qreal ratio = sanitizeDevicePixelRatio(this->devicePixelRatioF());
+    const QSize physicalSize(qRound(logicalSize.width() * ratio), qRound(logicalSize.height() * ratio));
+    emit viewportSizeChanged(physicalSize.width(), physicalSize.height());
+    emit displayScaleChanged(ratio);
+}
+
 void RdpDisplayWidget::keyPressEvent(QKeyEvent* event)
 {
     if (event == nullptr) {

src/rdp_display_widget.h

@@ -8,6 +8,7 @@ class QKeyEvent;
 class QMouseEvent;
 class QPaintEvent;
 class QResizeEvent;
+class QTimer;
 class QWheelEvent;
 
 class RdpDisplayWidget : public QWidget
@@ -30,10 +31,12 @@ signals:
     void mouseButtonInput(int x, int y, int button, bool pressed);
     void mouseWheelInput(int x, int y, int deltaX, int deltaY);
     void viewportSizeChanged(int width, int height);
+    void displayScaleChanged(qreal devicePixelRatio);
 
 protected:
     void paintEvent(QPaintEvent* event) override;
     void resizeEvent(QResizeEvent* event) override;
+    bool event(QEvent* event) override;
     void keyPressEvent(QKeyEvent* event) override;
     void keyReleaseEvent(QKeyEvent* event) override;
     void mousePressEvent(QMouseEvent* event) override;
@@ -54,11 +57,14 @@ private:
     QImage m_cursorImage;
     QPoint m_cursorHotspot;
     CursorMode m_cursorMode;
+    QTimer* m_resizeDebounceTimer;
 
     QRectF renderRect() const;
     QPoint mapToRemote(const QPointF& pos) const;
     QSize effectiveRemoteSize() const;
     void applyCursor();
+    void emitViewportGeometry();
+    void scheduleViewportGeometryEmit();
 };
 
 #endif

src/rdp_session_backend.cpp

@@ -89,43 +89,13 @@ constexpr double kDefaultDpi = 96.0;
 constexpr double kMillimetersPerInch = 25.4;
 
 #ifdef ORBITHUB_HAS_FREERDP
-QString normalizedRdpSecurityMode(const QString& value)
-{
-    const QString mode = value.trimmed();
-    if (mode.compare(QStringLiteral("NLA"), Qt::CaseInsensitive) == 0) {
-        return QStringLiteral("NLA");
-    }
-    if (mode.compare(QStringLiteral("TLS"), Qt::CaseInsensitive) == 0) {
-        return QStringLiteral("TLS");
-    }
-    if (mode.compare(QStringLiteral("RDP"), Qt::CaseInsensitive) == 0) {
-        return QStringLiteral("RDP");
-    }
-    return QStringLiteral("Negotiate");
-}
-
-QString normalizedRdpPerformanceProfile(const QString& value)
-{
-    const QString profile = value.trimmed();
-    if (profile.compare(QStringLiteral("Best Quality"), Qt::CaseInsensitive) == 0) {
-        return QStringLiteral("Best Quality");
-    }
-    if (profile.compare(QStringLiteral("Best Performance"), Qt::CaseInsensitive) == 0) {
-        return QStringLiteral("Best Performance");
-    }
-    if (profile.compare(QStringLiteral("Auto Detect"), Qt::CaseInsensitive) == 0) {
-        return QStringLiteral("Auto Detect");
-    }
-    return QStringLiteral("Balanced");
-}
-
 bool applyRdpSecurityMode(rdpSettings* settings, const QString& mode)
 {
     if (settings == nullptr) {
         return false;
     }
 
-    const QString normalized = normalizedRdpSecurityMode(mode);
+    const QString normalized = RdpSessionBackend::normalizedRdpSecurityMode(mode);
 
     BOOL rdp = FALSE;
     BOOL tls = FALSE;
@@ -159,7 +129,7 @@ bool applyRdpPerformanceProfile(rdpSettings* settings, const QString& profile)
         return false;
     }
 
-    const QString normalized = normalizedRdpPerformanceProfile(profile);
+    const QString normalized = RdpSessionBackend::normalizedRdpPerformanceProfile(profile);
     UINT32 connectionType = CONNECTION_TYPE_BROADBAND_HIGH;
     BOOL networkAutoDetect = FALSE;
     if (normalized == QStringLiteral("Best Quality")) {
@@ -859,8 +829,55 @@ BOOL orbitAuthenticateEx(freerdp* instance,
 
     return TRUE;
 }
+}
 
-UINT32 scancodeFromNativeScanCode(quint32 nativeScanCode)
+QString RdpSessionBackend::normalizedRdpSecurityMode(const QString& value)
+{
+    const QString mode = value.trimmed();
+    if (mode.compare(QStringLiteral("NLA"), Qt::CaseInsensitive) == 0) {
+        return QStringLiteral("NLA");
+    }
+    if (mode.compare(QStringLiteral("TLS"), Qt::CaseInsensitive) == 0) {
+        return QStringLiteral("TLS");
+    }
+    if (mode.compare(QStringLiteral("RDP"), Qt::CaseInsensitive) == 0) {
+        return QStringLiteral("RDP");
+    }
+    return QStringLiteral("Negotiate");
+}
+
+// MS-RDPEDISP restricts DesktopScaleFactor/DeviceScaleFactor to exactly
+// these three values; FreeRDP's own reference client enforces the same
+// set (client/common/cmdline.c, parse_scale_options). Anything else is
+// silently ignored by the server, so map the real, continuous
+// devicePixelRatio down to the nearest one.
+quint32 RdpSessionBackend::nearestFreeRdpScaleValue(qreal ratio)
+{
+    if (ratio <= 1.2) {
+        return 100;
+    }
+    if (ratio <= 1.6) {
+        return 140;
+    }
+    return 180;
+}
+
+QString RdpSessionBackend::normalizedRdpPerformanceProfile(const QString& value)
+{
+    const QString profile = value.trimmed();
+    if (profile.compare(QStringLiteral("Best Quality"), Qt::CaseInsensitive) == 0) {
+        return QStringLiteral("Best Quality");
+    }
+    if (profile.compare(QStringLiteral("Best Performance"), Qt::CaseInsensitive) == 0) {
+        return QStringLiteral("Best Performance");
+    }
+    if (profile.compare(QStringLiteral("Auto Detect"), Qt::CaseInsensitive) == 0) {
+        return QStringLiteral("Auto Detect");
+    }
+    return QStringLiteral("Balanced");
+}
+
+quint32 RdpSessionBackend::scancodeFromNativeScanCode(quint32 nativeScanCode)
 {
     if (nativeScanCode == 0) {
         return RDP_SCANCODE_UNKNOWN;
@@ -919,10 +936,12 @@ UINT32 scancodeFromNativeScanCode(quint32 nativeScanCode)
 #endif
 }
 
-UINT32 scancodeForQtKey(int key, Qt::KeyboardModifiers modifiers, quint32 nativeScanCode)
+quint32 RdpSessionBackend::scancodeForQtKey(int key,
+                                            Qt::KeyboardModifiers modifiers,
+                                            quint32 nativeScanCode)
 {
     const bool keypad = modifiers.testFlag(Qt::KeypadModifier);
-    const UINT32 nativeScancode = scancodeFromNativeScanCode(nativeScanCode);
+    const quint32 nativeScancode = scancodeFromNativeScanCode(nativeScanCode);
 
     switch (key) {
     case Qt::Key_Escape:
@@ -1147,7 +1166,7 @@ UINT32 scancodeForQtKey(int key, Qt::KeyboardModifiers modifiers, quint32 native
     }
 }
 
-QString mapRdpError(UINT32 code)
+QString RdpSessionBackend::mapRdpError(quint32 code)
 {
     switch (code) {
     case FREERDP_ERROR_CONNECT_LOGON_FAILURE:
@@ -1210,7 +1229,7 @@ QString mapRdpError(UINT32 code)
     return QStringLiteral("RDP connection failed (0x%1).").arg(code, 8, 16, QChar('0'));
 }
 
-bool isExpectedDisconnectCode(UINT32 code)
+bool RdpSessionBackend::isExpectedDisconnectCode(quint32 code)
 {
     switch (code) {
     case FREERDP_ERROR_SUCCESS:
@@ -1240,7 +1259,7 @@ bool isExpectedDisconnectCode(UINT32 code)
     }
 }
 
-bool isExpectedConnectAbortCode(UINT32 code)
+bool RdpSessionBackend::isExpectedConnectAbortCode(quint32 code)
 {
     switch (code) {
     case FREERDP_ERROR_SUCCESS:
@@ -1252,7 +1271,7 @@ bool isExpectedConnectAbortCode(UINT32 code)
     }
 }
 
-QString disconnectMessageForCode(UINT32 code)
+QString RdpSessionBackend::disconnectMessageForCode(quint32 code)
 {
     switch (code) {
     case FREERDP_ERROR_IDLE_TIMEOUT:
@@ -1288,7 +1307,7 @@ QString disconnectMessageForCode(UINT32 code)
     }
 }
 
-QString rdpErrorRaw(UINT32 code)
+QString RdpSessionBackend::rdpErrorRaw(quint32 code)
 {
     const char* name = freerdp_get_last_error_name(code);
     const QString text = (name != nullptr && name[0] != '\0') ? QString::fromUtf8(name)
@@ -1296,7 +1315,6 @@ QString rdpErrorRaw(UINT32 code)
     return QStringLiteral("%1 (0x%2)").arg(text).arg(code, 8, 16, QChar('0'));
 }
 #endif
-}
 
 RdpSessionBackend::RdpSessionBackend(const Profile& profile, QObject* parent)
     : SessionBackend(profile, parent),
@@ -1304,6 +1322,7 @@ RdpSessionBackend::RdpSessionBackend(const Profile& profile, QObject* parent)
       m_userInitiatedDisconnect(false),
       m_requestedDesktopWidth(kDefaultDesktopWidth),
       m_requestedDesktopHeight(kDefaultDesktopHeight),
+      m_devicePixelRatio(1.0),
       m_workerRunning(false),
       m_stopRequested(false),
       m_instance(nullptr),
@@ -1312,6 +1331,7 @@ RdpSessionBackend::RdpSessionBackend(const Profile& profile, QObject* parent)
       m_resizeFailureLogged(false),
       m_lastResizeWidth(0),
       m_lastResizeHeight(0),
+      m_lastResizeScale(0),
       m_cliprdrContext(nullptr)
 {
 }
@@ -1403,6 +1423,28 @@ void RdpSessionBackend::updateTerminalSize(int columns, int rows)
     enqueueInputEvent(event);
 }
 
+void RdpSessionBackend::updateDisplayScale(qreal devicePixelRatio)
+{
+    const qreal clamped = qBound(1.0, devicePixelRatio, 4.0);
+    m_devicePixelRatio.store(clamped);
+
+    if (!m_workerRunning.load()) {
+        return;
+    }
+
+    // Reuses the resize input-event path so the worker thread (which owns
+    // m_instance) picks this up safely; processInputEvents' dedup check
+    // also compares the quantized scale value, so this correctly triggers
+    // a fresh SendMonitorLayout even when width/height haven't changed
+    // (e.g. the window moved to a different-DPI monitor at the same
+    // logical size).
+    InputEvent event;
+    event.type = InputEventType::Resize;
+    event.width = sanitizeDesktopWidth(m_requestedDesktopWidth.load());
+    event.height = sanitizeDesktopHeight(m_requestedDesktopHeight.load());
+    enqueueInputEvent(event);
+}
+
 void RdpSessionBackend::sendKeyEvent(int key,
                                      quint32 nativeScanCode,
                                      const QString& text,
@@ -1637,9 +1679,29 @@ void RdpSessionBackend::workerMain()
     const QString performanceProfile = normalizedRdpPerformanceProfile(p.rdpPerformanceProfile);
     freerdp_settings_set_bool(settings, FreeRDP_SupportDisplayControl, TRUE);
     freerdp_settings_set_bool(settings, FreeRDP_DynamicResolutionUpdate, TRUE);
+    // Lets us actively request a full-screen repaint after a resize (see
+    // sendDisplayResize) — some RDP hosts (particularly VMs using a
+    // synthetic/virtual display driver) occasionally fail to fully redraw
+    // their own desktop after a resolution change; requesting a refresh
+    // forces them to resend everything rather than leaving stale content.
+    freerdp_settings_set_bool(settings, FreeRDP_RefreshRect, TRUE);
     freerdp_settings_set_uint32(settings, FreeRDP_DesktopWidth, static_cast<UINT32>(desktopWidth));
     freerdp_settings_set_uint32(settings, FreeRDP_DesktopHeight, static_cast<UINT32>(desktopHeight));
     freerdp_settings_set_uint32(settings, FreeRDP_ColorDepth, 32);
+    // Tell the remote session the real display scale so it renders its own
+    // UI/ClearType text natively at that size, instead of assuming 96 DPI
+    // and having the result stretched (and ClearType's subpixel hinting
+    // distorted) by client-side scaling. The override flags are required —
+    // without them FreeRDP ignores the scale factor values entirely.
+    {
+        const UINT32 scaleValue = nearestFreeRdpScaleValue(m_devicePixelRatio.load());
+        freerdp_settings_set_uint32(settings, FreeRDP_DesktopScaleFactor, scaleValue);
+        freerdp_settings_set_uint32(settings, FreeRDP_DeviceScaleFactor, scaleValue);
+        freerdp_settings_set_uint64(settings,
+                                     FreeRDP_MonitorOverrideFlags,
+                                     FREERDP_MONITOR_OVERRIDE_DESKTOP_SCALE
+                                         | FREERDP_MONITOR_OVERRIDE_DEVICE_SCALE);
+    }
     freerdp_settings_set_bool(settings, FreeRDP_AuthenticationOnly, FALSE);
     freerdp_settings_set_bool(settings, FreeRDP_AutoLogonEnabled, TRUE);
     if (!applyRdpSecurityMode(settings, securityMode)) {
@@ -1831,9 +1893,14 @@ bool RdpSessionBackend::sendDisplayResize(rdp_freerdp* instance, int width, int
         return false;
     }
 
+    const qreal ratio = m_devicePixelRatio.load();
+    const UINT32 scaleValue = nearestFreeRdpScaleValue(ratio);
+
     rdpSettings* settings = instance->context->settings;
     freerdp_settings_set_uint32(settings, FreeRDP_DesktopWidth, static_cast<UINT32>(width));
     freerdp_settings_set_uint32(settings, FreeRDP_DesktopHeight, static_cast<UINT32>(height));
+    freerdp_settings_set_uint32(settings, FreeRDP_DesktopScaleFactor, scaleValue);
+    freerdp_settings_set_uint32(settings, FreeRDP_DeviceScaleFactor, scaleValue);
 
     DispClientContext* dispContext = nullptr;
     bool displayControlReady = false;
@@ -1851,17 +1918,58 @@ bool RdpSessionBackend::sendDisplayResize(rdp_freerdp* instance, int width, int
         layout.Width = static_cast<UINT32>(width);
         layout.Height = static_cast<UINT32>(height);
         layout.Orientation = ORIENTATION_LANDSCAPE;
-        layout.DesktopScaleFactor = freerdp_settings_get_uint32(settings, FreeRDP_DesktopScaleFactor);
+        layout.DesktopScaleFactor = scaleValue;
-        layout.DeviceScaleFactor = freerdp_settings_get_uint32(settings, FreeRDP_DeviceScaleFactor);
+        layout.DeviceScaleFactor = scaleValue;
+        // Physical size in mm must reflect the real DPI (96 * ratio), not
+        // the plain baseline, so it stays consistent with the scale factor
+        // above rather than implying a standard-DPI display of this size.
+        const double effectiveDpi = kDefaultDpi * ratio;
         layout.PhysicalWidth = static_cast<UINT32>(
-            std::lround((static_cast<double>(width) / kDefaultDpi) * kMillimetersPerInch));
+            std::lround((static_cast<double>(width) / effectiveDpi) * kMillimetersPerInch));
         layout.PhysicalHeight = static_cast<UINT32>(
-            std::lround((static_cast<double>(height) / kDefaultDpi) * kMillimetersPerInch));
+            std::lround((static_cast<double>(height) / effectiveDpi) * kMillimetersPerInch));
 
         const UINT rc = dispContext->SendMonitorLayout(dispContext, 1, &layout);
         if (rc == CHANNEL_RC_OK) {
             m_lastResizeWidth = width;
             m_lastResizeHeight = height;
+            m_lastResizeScale = static_cast<int>(scaleValue);
+
+            // The Display Control channel (MS-RDPEDISP) has no server
+            // acknowledgment PDU, and real hosts apply the new resolution
+            // without a Deactivation-Reactivation sequence — so
+            // update->DesktopResize (which only fires for that sequence, or
+            // for the GFX/Progressive pipeline we don't use) never runs for
+            // a channel-driven resize. Without a matching gdi_resize() call,
+            // gdi->width/height stay at the old size, and FreeRDP's own
+            // surface-bits handling (intersect_rect in gdi.c) then silently
+            // *drops* any update reaching outside those stale bounds —
+            // which is what produced the missing/misplaced taskbar and
+            // stale composited-looking content: this call is the fix, not
+            // just a best-effort nudge.
+            if (instance->context->gdi != nullptr
+                && gdi_resize(instance->context->gdi, static_cast<UINT32>(width),
+                              static_cast<UINT32>(height))) {
+                emit remoteDesktopSizeChanged(width, height);
+            } else if (instance->context->gdi != nullptr) {
+                emit eventLogged(QStringLiteral(
+                    "RDP warning: local resize to %1x%2 failed; display may show stale content "
+                    "until the next full repaint.")
+                                     .arg(width)
+                                     .arg(height));
+            }
+
+            // Best-effort nudge: some hosts don't fully repaint their own
+            // desktop after a resolution change (observed: taskbar missing
+            // until something else forces a redraw). Explicitly asking for
+            // the whole new area to be resent costs little and helps
+            // recover from that when it happens.
+            if (instance->context->update != nullptr
+                && instance->context->update->RefreshRect != nullptr) {
+                RECTANGLE_16 fullArea = {0, 0, static_cast<UINT16>(qMin(width, 65535)),
+                                         static_cast<UINT16>(qMin(height, 65535))};
+                instance->context->update->RefreshRect(instance->context, 1, &fullArea);
+            }
             return true;
         }
     }
@@ -2035,7 +2143,9 @@ void RdpSessionBackend::processInputEvents(rdp_freerdp* instance)
     if (hasResize) {
         const int width = sanitizeDesktopWidth(resizeWidth);
         const int height = sanitizeDesktopHeight(resizeHeight);
-        if (width != m_lastResizeWidth || height != m_lastResizeHeight) {
+        const int scaleValue = static_cast<int>(nearestFreeRdpScaleValue(m_devicePixelRatio.load()));
+        if (width != m_lastResizeWidth || height != m_lastResizeHeight
+            || scaleValue != m_lastResizeScale) {
             if (sendDisplayResize(instance, width, height)) {
                 if (m_resizeFailureLogged) {
                     emit eventLogged(QStringLiteral("Dynamic RDP resize recovered."));
@@ -2326,7 +2436,7 @@ void RdpSessionBackend::emitConnectionFailureAsync(const QString& displayMessage
         Qt::QueuedConnection);
 }
 
-int RdpSessionBackend::sanitizeDesktopWidth(int width) const
+int RdpSessionBackend::sanitizeDesktopWidth(int width)
 {
     if (width <= 0) {
         return kDefaultDesktopWidth;
@@ -2334,7 +2444,7 @@ int RdpSessionBackend::sanitizeDesktopWidth(int width) const
     return qBound(kMinDesktopWidth, width, kMaxDesktopWidth);
 }
 
-int RdpSessionBackend::sanitizeDesktopHeight(int height) const
+int RdpSessionBackend::sanitizeDesktopHeight(int height)
 {
     if (height <= 0) {
         return kDefaultDesktopHeight;

src/rdp_session_backend.h

@@ -19,6 +19,24 @@ public:
     explicit RdpSessionBackend(const Profile& profile, QObject* parent = nullptr);
     ~RdpSessionBackend() override;
 
+    // Pure, state-free helpers exposed as public statics purely so tests
+    // can exercise them without a live FreeRDP connection. UINT32 values
+    // are surfaced as quint32 here to keep FreeRDP/WinPR types out of this
+    // header (uint32_t is what UINT32 always is on every platform this
+    // project targets).
+    static QString normalizedRdpSecurityMode(const QString& value);
+    static QString normalizedRdpPerformanceProfile(const QString& value);
+    static quint32 nearestFreeRdpScaleValue(qreal ratio);
+    static quint32 scancodeFromNativeScanCode(quint32 nativeScanCode);
+    static quint32 scancodeForQtKey(int key, Qt::KeyboardModifiers modifiers, quint32 nativeScanCode);
+    static QString mapRdpError(quint32 code);
+    static bool isExpectedDisconnectCode(quint32 code);
+    static bool isExpectedConnectAbortCode(quint32 code);
+    static QString disconnectMessageForCode(quint32 code);
+    static QString rdpErrorRaw(quint32 code);
+    static int sanitizeDesktopWidth(int width);
+    static int sanitizeDesktopHeight(int height);
+
 public slots:
     void connectSession(const SessionConnectOptions& options) override;
     void disconnectSession() override;
@@ -26,6 +44,7 @@ public slots:
     void sendInput(const QString& input) override;
     void confirmHostKey(bool trustHost) override;
     void updateTerminalSize(int columns, int rows) override;
+    void updateDisplayScale(qreal devicePixelRatio) override;
     void sendKeyEvent(int key,
                       quint32 nativeScanCode,
                       const QString& text,
@@ -68,6 +87,7 @@ private:
 
     std::atomic_int m_requestedDesktopWidth;
     std::atomic_int m_requestedDesktopHeight;
+    std::atomic<qreal> m_devicePixelRatio;
 
     std::thread m_worker;
     std::atomic_bool m_workerRunning;
@@ -85,6 +105,7 @@ private:
     bool m_resizeFailureLogged;
     int m_lastResizeWidth;
     int m_lastResizeHeight;
+    int m_lastResizeScale;
 
     std::mutex m_cliprdrMutex;
     void* m_cliprdrContext;
@@ -121,8 +142,6 @@ public:
 private:
     void emitStateAsync(SessionState state, const QString& message);
     void emitConnectionFailureAsync(const QString& displayMessage, const QString& rawMessage);
-    int sanitizeDesktopWidth(int width) const;
-    int sanitizeDesktopHeight(int height) const;
 };
 
 #endif

src/session_backend.h

@@ -47,10 +47,24 @@ public slots:
     virtual void sendInput(const QString& input) = 0;
     virtual void confirmHostKey(bool trustHost) = 0;
     virtual void updateTerminalSize(int columns, int rows) = 0;
+    virtual void updateDisplayScale(qreal devicePixelRatio)
+    {
+        Q_UNUSED(devicePixelRatio);
+    }
     virtual void setClipboardText(const QString& text)
     {
         Q_UNUSED(text);
     }
+    // Response to usernameRequested(), for backends that discover mid-
+    // connection (not before connectSession() is even called) that they
+    // need one -- currently only VNC's Apple authentication schemes,
+    // which only require a username for security types 30/33, not for
+    // plain VNC Authentication or no-auth. An empty username is treated
+    // the same as the prompt being cancelled.
+    virtual void provideUsername(const QString& username)
+    {
+        Q_UNUSED(username);
+    }
     virtual void sendKeyEvent(int key,
                               quint32 nativeScanCode,
                               const QString& text,
@@ -89,6 +103,10 @@ signals:
     void connectionError(const QString& displayMessage, const QString& rawMessage);
     void outputReceived(const QString& text);
     void hostKeyConfirmationRequested(const QString& prompt);
+    // Mirrors hostKeyConfirmationRequested()'s request/response shape, for
+    // a backend that discovers mid-connection it needs a username it
+    // wasn't given -- see provideUsername().
+    void usernameRequested(const QString& prompt);
     void frameUpdated(const QImage& frame);
     void remoteDesktopSizeChanged(int width, int height);
     void remoteClipboardTextChanged(const QString& text);

src/session_backend_factory.cpp

@@ -4,6 +4,7 @@
 #include "session_backend.h"
 #include "ssh_session_backend.h"
 #include "unsupported_session_backend.h"
+#include "vnc_session_backend.h"
 
 std::unique_ptr<SessionBackend> createSessionBackend(const Profile& profile)
 {
@@ -13,6 +14,9 @@ std::unique_ptr<SessionBackend> createSessionBackend(const Profile& profile)
     if (profile.protocol.compare(QStringLiteral("RDP"), Qt::CaseInsensitive) == 0) {
         return std::make_unique<RdpSessionBackend>(profile);
     }
+    if (profile.protocol.compare(QStringLiteral("VNC"), Qt::CaseInsensitive) == 0) {
+        return std::make_unique<VncSessionBackend>(profile);
+    }
 
     return std::make_unique<UnsupportedSessionBackend>(profile);
 }

src/session_tab.cpp

@@ -3,6 +3,7 @@
 #include "rdp_display_widget.h"
 #include "session_backend_factory.h"
 #include "terminal_view.h"
+#include "vnc_display_widget.h"
 
 #include <KodoTerm/KodoTerm.hpp>
 
@@ -23,6 +24,7 @@
 #include <QComboBox>
 #include <QProcessEnvironment>
 #include <QPushButton>
+#include <QScrollArea>
 #include <QThread>
 #include <QTimer>
 #include <QToolButton>
@@ -75,10 +77,13 @@ SessionTab::SessionTab(const Profile& profile,
       m_terminalFontPointSize(preferences.terminalFontPointSize > 0
                                   ? preferences.terminalFontPointSize
                                   : 0),
-      m_clipboardSyncSupported(profile.protocol.compare(QStringLiteral("RDP"), Qt::CaseInsensitive)
+      m_clipboardSyncSupported(
-                                == 0),
+          profile.protocol.compare(QStringLiteral("RDP"), Qt::CaseInsensitive) == 0
+          || profile.protocol.compare(QStringLiteral("VNC"), Qt::CaseInsensitive) == 0),
       m_sshTerminal(nullptr),
       m_rdpDisplay(nullptr),
+      m_vncDisplay(nullptr),
+      m_vncScrollArea(nullptr),
       m_terminalOutput(nullptr),
       m_eventLog(nullptr),
       m_toggleEventsButton(nullptr),
@@ -100,6 +105,10 @@ SessionTab::SessionTab(const Profile& profile,
 
     setupUi();
 
+    if (m_vncDisplay != nullptr) {
+        m_vncDisplay->setScaleToFit(preferences.vncScaleToFit);
+    }
+
     if (m_useKodoTermForSsh) {
         connect(m_sshTerminal,
                 &KodoTerm::finished,
@@ -176,6 +185,11 @@ SessionTab::SessionTab(const Profile& profile,
                 m_backend,
                 &SessionBackend::updateTerminalSize,
                 Qt::QueuedConnection);
+        connect(this,
+                &SessionTab::requestDisplayScale,
+                m_backend,
+                &SessionBackend::updateDisplayScale,
+                Qt::QueuedConnection);
         connect(this,
                 &SessionTab::requestKeyEvent,
                 m_backend,
@@ -201,6 +215,11 @@ SessionTab::SessionTab(const Profile& profile,
                 m_backend,
                 &SessionBackend::setClipboardText,
                 Qt::QueuedConnection);
+        connect(this,
+                &SessionTab::requestProvideUsername,
+                m_backend,
+                &SessionBackend::provideUsername,
+                Qt::QueuedConnection);
 
         connect(m_backend,
                 &SessionBackend::stateChanged,
@@ -227,12 +246,19 @@ SessionTab::SessionTab(const Profile& profile,
                 this,
                 &SessionTab::onBackendHostKeyConfirmationRequested,
                 Qt::QueuedConnection);
+        connect(m_backend,
+                &SessionBackend::usernameRequested,
+                this,
+                &SessionTab::onBackendUsernameRequested,
+                Qt::QueuedConnection);
         connect(m_backend,
                 &SessionBackend::frameUpdated,
                 this,
                 [this](const QImage& frame) {
                     if (m_rdpDisplay != nullptr) {
                         m_rdpDisplay->setFrame(frame);
+                    } else if (m_vncDisplay != nullptr) {
+                        m_vncDisplay->setFrame(frame);
                     }
                 },
                 Qt::QueuedConnection);
@@ -242,6 +268,8 @@ SessionTab::SessionTab(const Profile& profile,
                 [this](int width, int height) {
                     if (m_rdpDisplay != nullptr) {
                         m_rdpDisplay->setRemoteDesktopSize(width, height);
+                    } else if (m_vncDisplay != nullptr) {
+                        m_vncDisplay->setRemoteDesktopSize(width, height);
                     }
                 },
                 Qt::QueuedConnection);
@@ -256,6 +284,8 @@ SessionTab::SessionTab(const Profile& profile,
                 [this](const QImage& image, const QPoint& hotspot) {
                     if (m_rdpDisplay != nullptr) {
                         m_rdpDisplay->setCursorImage(image, hotspot);
+                    } else if (m_vncDisplay != nullptr) {
+                        m_vncDisplay->setCursorImage(image, hotspot);
                     }
                 },
                 Qt::QueuedConnection);
@@ -265,6 +295,8 @@ SessionTab::SessionTab(const Profile& profile,
                 [this]() {
                     if (m_rdpDisplay != nullptr) {
                         m_rdpDisplay->setCursorHidden();
+                    } else if (m_vncDisplay != nullptr) {
+                        m_vncDisplay->setCursorHidden();
                     }
                 },
                 Qt::QueuedConnection);
@@ -274,6 +306,8 @@ SessionTab::SessionTab(const Profile& profile,
                 [this]() {
                     if (m_rdpDisplay != nullptr) {
                         m_rdpDisplay->setCursorDefault();
+                    } else if (m_vncDisplay != nullptr) {
+                        m_vncDisplay->setCursorDefault();
                     }
                 },
                 Qt::QueuedConnection);
@@ -400,6 +434,12 @@ void SessionTab::clearTerminal()
     if (m_rdpDisplay != nullptr) {
         m_rdpDisplay->clearFrame();
         m_rdpDisplay->setFocus();
+        return;
+    }
+
+    if (m_vncDisplay != nullptr) {
+        m_vncDisplay->clearFrame();
+        m_vncDisplay->setFocus();
     }
 }
 
@@ -440,6 +480,28 @@ bool SessionTab::supportsZoom() const
     return m_useKodoTermForSsh || m_terminalOutput != nullptr;
 }
 
+bool SessionTab::supportsVncScaleToggle() const
+{
+    return m_vncDisplay != nullptr;
+}
+
+void SessionTab::setVncScaleToFit(bool scaleToFit)
+{
+    if (m_vncDisplay == nullptr || m_vncDisplay->scaleToFit() == scaleToFit) {
+        return;
+    }
+
+    m_vncDisplay->setScaleToFit(scaleToFit);
+    appendEvent(scaleToFit ? QStringLiteral("Display mode set to scale to fit.")
+                          : QStringLiteral("Display mode set to actual size."));
+    emit vncScaleModeChanged(scaleToFit);
+}
+
+bool SessionTab::vncScaleToFit() const
+{
+    return m_vncDisplay != nullptr ? m_vncDisplay->scaleToFit() : true;
+}
+
 void SessionTab::zoomIn()
 {
     if (m_useKodoTermForSsh && m_sshTerminal != nullptr) {
@@ -662,6 +724,16 @@ void SessionTab::onBackendHostKeyConfirmationRequested(const QString& prompt)
     emit requestHostKeyConfirmation(reply == QMessageBox::Yes);
 }
 
+void SessionTab::onBackendUsernameRequested(const QString& prompt)
+{
+    showPasswordPrompt(
+        prompt.isEmpty() ? QStringLiteral("Username for %1:").arg(m_profile.host) : prompt,
+        [this](std::optional<QString> username) {
+            emit requestProvideUsername(username.value_or(QString()).trimmed());
+        },
+        false);
+}
+
 void SessionTab::onBackendRemoteClipboardTextChanged(const QString& text)
 {
     if (text == m_lastSyncedClipboardText) {
@@ -712,6 +784,13 @@ void SessionTab::setupUi()
     } else if (m_profile.protocol.compare(QStringLiteral("RDP"), Qt::CaseInsensitive) == 0) {
         m_rdpDisplay = new RdpDisplayWidget(this);
         rootLayout->addWidget(m_rdpDisplay, 1);
+    } else if (m_profile.protocol.compare(QStringLiteral("VNC"), Qt::CaseInsensitive) == 0) {
+        m_vncDisplay = new VncDisplayWidget(this);
+        m_vncScrollArea = new QScrollArea(this);
+        m_vncScrollArea->setWidget(m_vncDisplay);
+        m_vncScrollArea->setWidgetResizable(true);
+        m_vncScrollArea->setFrameShape(QFrame::NoFrame);
+        rootLayout->addWidget(m_vncScrollArea, 1);
     } else {
         m_terminalOutput = new TerminalView(this);
         QFont fallbackFont = defaultTerminalFont();
@@ -721,13 +800,7 @@ void SessionTab::setupUi()
         m_terminalOutput->setFont(fallbackFont);
         m_terminalOutput->setMinimumHeight(260);
         m_terminalOutput->setReadOnly(true);
-        if (m_profile.protocol.compare(QStringLiteral("VNC"), Qt::CaseInsensitive) == 0) {
+        m_terminalOutput->setPlaceholderText(QStringLiteral("Session output appears here."));
-            m_terminalOutput->setPlaceholderText(
-                QStringLiteral("Embedded VNC session output appears here when the backend is available."));
-        } else {
-            m_terminalOutput->setPlaceholderText(
-                QStringLiteral("Session output appears here."));
-        }
         rootLayout->addWidget(m_terminalOutput, 1);
     }
 
@@ -860,6 +933,10 @@ void SessionTab::setupUi()
                 &RdpDisplayWidget::viewportSizeChanged,
                 this,
                 [this](int width, int height) { emit requestTerminalSize(width, height); });
+        connect(m_rdpDisplay,
+                &RdpDisplayWidget::displayScaleChanged,
+                this,
+                [this](qreal ratio) { emit requestDisplayScale(ratio); });
         connect(m_rdpDisplay,
                 &RdpDisplayWidget::keyInput,
                 this,
@@ -882,6 +959,37 @@ void SessionTab::setupUi()
                 [this](int x, int y, int deltaX, int deltaY) {
                     emit requestMouseWheelEvent(x, y, deltaX, deltaY);
                 });
+    } else if (m_vncDisplay != nullptr) {
+        connect(m_vncDisplay,
+                &VncDisplayWidget::viewportSizeChanged,
+                this,
+                [this](int width, int height) { emit requestTerminalSize(width, height); });
+        connect(m_vncDisplay,
+                &VncDisplayWidget::displayScaleChanged,
+                this,
+                [this](qreal ratio) { emit requestDisplayScale(ratio); });
+        connect(m_vncDisplay,
+                &VncDisplayWidget::keyInput,
+                this,
+                [this](int key, quint32 nativeScanCode, const QString& text, bool pressed, int modifiers) {
+                    emit requestKeyEvent(key, nativeScanCode, text, pressed, modifiers);
+                });
+        connect(m_vncDisplay,
+                &VncDisplayWidget::mouseMoveInput,
+                this,
+                [this](int x, int y) { emit requestMouseMoveEvent(x, y); });
+        connect(m_vncDisplay,
+                &VncDisplayWidget::mouseButtonInput,
+                this,
+                [this](int x, int y, int button, bool pressed) {
+                    emit requestMouseButtonEvent(x, y, button, pressed);
+                });
+        connect(m_vncDisplay,
+                &VncDisplayWidget::mouseWheelInput,
+                this,
+                [this](int x, int y, int deltaX, int deltaY) {
+                    emit requestMouseWheelEvent(x, y, deltaX, deltaY);
+                });
     }
 }
 
@@ -893,6 +1001,48 @@ void SessionTab::requestConnectOptions(
 
     const bool isSsh = m_profile.protocol.compare(QStringLiteral("SSH"), Qt::CaseInsensitive) == 0;
     const bool isRdp = m_profile.protocol.compare(QStringLiteral("RDP"), Qt::CaseInsensitive) == 0;
+    const bool isVnc = m_profile.protocol.compare(QStringLiteral("VNC"), Qt::CaseInsensitive) == 0;
+
+    // SSH and RDP always need a username; a profile is now allowed to
+    // leave it blank (see profile_dialog.cpp) and get asked here instead,
+    // the same way a blank password is already handled below. The value
+    // is kept on this in-memory m_profile copy for the rest of the tab's
+    // lifetime, not written back to the saved profile.
+    if ((isSsh || isRdp) && m_profile.username.trimmed().isEmpty()) {
+        showPasswordPrompt(
+            QStringLiteral("%1 username for %2:").arg(m_profile.protocol, m_profile.host),
+            [this, callback](std::optional<QString> username) {
+                if (!username.has_value() || username->trimmed().isEmpty()) {
+                    callback(std::nullopt);
+                    return;
+                }
+                m_profile.username = username->trimmed();
+                requestConnectOptions(callback);
+            },
+            false);
+        return;
+    }
+
+    if (isVnc) {
+        // Unlike RDP, an empty password is allowed through: some VNC
+        // servers (no-auth) don't need one at all, and there's no
+        // client-side way to know that before the server's security-type
+        // negotiation happens.
+        showPasswordPrompt(
+            QStringLiteral("VNC password for %1 (leave blank if the server doesn't require one):")
+                .arg(m_profile.host),
+            [baseOptions, callback](std::optional<QString> password) {
+                if (!password.has_value()) {
+                    callback(std::nullopt);
+                    return;
+                }
+
+                SessionConnectOptions options = baseOptions;
+                options.password = password.value();
+                callback(options);
+            });
+        return;
+    }
 
     if (!isSsh && !isRdp) {
         callback(baseOptions);
@@ -992,7 +1142,8 @@ void SessionTab::requestConnectOptions(
 }
 
 void SessionTab::showPasswordPrompt(const QString& labelText,
-                                    std::function<void(std::optional<QString>)> callback)
+                                    std::function<void(std::optional<QString>)> callback,
+                                    bool maskInput)
 {
     if (m_passwordPromptCallback) {
         const auto previousCallback = m_passwordPromptCallback;
@@ -1003,6 +1154,7 @@ void SessionTab::showPasswordPrompt(const QString& labelText,
     m_passwordPromptCallback = std::move(callback);
     m_passwordPromptLabel->setText(labelText);
     m_passwordPromptInput->clear();
+    m_passwordPromptInput->setEchoMode(maskInput ? QLineEdit::Password : QLineEdit::Normal);
     m_passwordPromptBar->setVisible(true);
     m_passwordPromptInput->setFocus();
 }
@@ -1101,6 +1253,14 @@ void SessionTab::refreshActionButtons()
         if (isConnected) {
             m_rdpDisplay->setFocus();
         }
+        return;
+    }
+
+    if (m_vncDisplay != nullptr) {
+        m_vncDisplay->setEnabled(isConnected);
+        if (isConnected) {
+            m_vncDisplay->setFocus();
+        }
     }
 }
 

src/session_tab.h

@@ -17,11 +17,13 @@ class QThread;
 class SessionBackend;
 class TerminalView;
 class RdpDisplayWidget;
+class VncDisplayWidget;
 class QToolButton;
 class QLineEdit;
 class QComboBox;
 class QLabel;
 class QPushButton;
+class QScrollArea;
 class KodoTerm;
 
 struct SessionUiPreferences
@@ -29,6 +31,7 @@ struct SessionUiPreferences
     QString terminalThemeName = QStringLiteral("Dark");
     bool eventsPanelExpanded = false;
     int terminalFontPointSize = 0;
+    bool vncScaleToFit = true;
 };
 
 class SessionTab : public QWidget
@@ -61,6 +64,9 @@ public:
     void clearEvents();
     void copyEvents() const;
     void exportEventsToFile();
+    bool supportsVncScaleToggle() const;
+    void setVncScaleToFit(bool scaleToFit);
+    bool vncScaleToFit() const;
 
 signals:
     void tabTitleChanged(const QString& title);
@@ -68,12 +74,14 @@ signals:
     void terminalThemeChanged(const QString& themeName);
     void terminalFontSizeChanged(int pointSize);
     void eventsPanelVisibilityChanged(bool expanded);
+    void vncScaleModeChanged(bool scaleToFit);
     void requestConnect(const SessionConnectOptions& options);
     void requestDisconnect();
     void requestReconnect(const SessionConnectOptions& options);
     void requestInput(const QString& input);
     void requestHostKeyConfirmation(bool trustHost);
     void requestTerminalSize(int columns, int rows);
+    void requestDisplayScale(qreal devicePixelRatio);
     void requestKeyEvent(int key,
                          quint32 nativeScanCode,
                          const QString& text,
@@ -83,6 +91,7 @@ signals:
     void requestMouseButtonEvent(int x, int y, int button, bool pressed);
     void requestMouseWheelEvent(int x, int y, int deltaX, int deltaY);
     void requestSetClipboardText(const QString& text);
+    void requestProvideUsername(const QString& username);
 
 private slots:
     void onBackendStateChanged(SessionState state, const QString& message);
@@ -90,6 +99,7 @@ private slots:
     void onBackendConnectionError(const QString& displayMessage, const QString& rawMessage);
     void onBackendOutputReceived(const QString& text);
     void onBackendHostKeyConfirmationRequested(const QString& prompt);
+    void onBackendUsernameRequested(const QString& prompt);
     void onBackendRemoteClipboardTextChanged(const QString& text);
     void onSystemClipboardChanged();
 
@@ -108,6 +118,8 @@ private:
 
     KodoTerm* m_sshTerminal;
     RdpDisplayWidget* m_rdpDisplay;
+    VncDisplayWidget* m_vncDisplay;
+    QScrollArea* m_vncScrollArea;
     TerminalView* m_terminalOutput;
     QPlainTextEdit* m_eventLog;
     QToolButton* m_toggleEventsButton;
@@ -139,7 +151,8 @@ private:
     void setupUi();
     void requestConnectOptions(std::function<void(std::optional<SessionConnectOptions>)> callback);
     void showPasswordPrompt(const QString& labelText,
-                            std::function<void(std::optional<QString>)> callback);
+                            std::function<void(std::optional<QString>)> callback,
+                            bool maskInput = true);
     void hidePasswordPrompt();
     bool validateProfileForConnect();
     void appendEvent(const QString& message);

src/session_window.cpp

@@ -120,6 +120,20 @@ SessionWindow::SessionWindow(QWidget* parent)
                     setFontSizeAction = menu.addAction(QStringLiteral("Set Font Size..."));
                 }
 
+                QAction* scaleToFitAction = nullptr;
+                QAction* actualSizeAction = nullptr;
+                if (tab->supportsVncScaleToggle()) {
+                    menu.addSeparator();
+                    QMenu* displayMenu = menu.addMenu(QStringLiteral("Display Mode"));
+                    scaleToFitAction = displayMenu->addAction(QStringLiteral("Scale to Fit"));
+                    scaleToFitAction->setCheckable(true);
+                    scaleToFitAction->setChecked(tab->vncScaleToFit());
+                    actualSizeAction = displayMenu->addAction(
+                        QStringLiteral("Actual Size (Scrollbars)"));
+                    actualSizeAction->setCheckable(true);
+                    actualSizeAction->setChecked(!tab->vncScaleToFit());
+                }
+
                 QAction* chosen = menu.exec(m_tabs->tabBar()->mapToGlobal(pos));
                 if (chosen == disconnectAction) {
                     tab->disconnectSession();
@@ -156,6 +170,10 @@ SessionWindow::SessionWindow(QWidget* parent)
                     if (accepted) {
                         tab->setTerminalFontPointSize(newSize);
                     }
+                } else if (scaleToFitAction != nullptr && chosen == scaleToFitAction) {
+                    tab->setVncScaleToFit(true);
+                } else if (actualSizeAction != nullptr && chosen == actualSizeAction) {
+                    tab->setVncScaleToFit(false);
                 } else {
                     for (QAction* themeAction : themeActions) {
                         if (chosen == themeAction) {
@@ -170,6 +188,10 @@ SessionWindow::SessionWindow(QWidget* parent)
     QAction* newProfileAction = fileMenu->addAction(QStringLiteral("New Profile"));
     QAction* newFolderAction = fileMenu->addAction(QStringLiteral("New Folder"));
     fileMenu->addSeparator();
+    QAction* importProfilesAction = fileMenu->addAction(QStringLiteral("Import Profiles..."));
+    QAction* exportProfilesAction = fileMenu->addAction(QStringLiteral("Export Profiles..."));
+    QAction* importMRemoteNGAction = fileMenu->addAction(QStringLiteral("Import from mRemoteNG..."));
+    fileMenu->addSeparator();
     QAction* quitAction = fileMenu->addAction(QStringLiteral("Quit"));
 
     connect(newProfileAction,
@@ -180,6 +202,18 @@ SessionWindow::SessionWindow(QWidget* parent)
             &QAction::triggered,
             this,
             [this]() { m_profilesWidget->createFolderInCurrentContext(); });
+    connect(importProfilesAction,
+            &QAction::triggered,
+            this,
+            [this]() { m_profilesWidget->importProfiles(); });
+    connect(exportProfilesAction,
+            &QAction::triggered,
+            this,
+            [this]() { m_profilesWidget->exportProfiles(); });
+    connect(importMRemoteNGAction,
+            &QAction::triggered,
+            this,
+            [this]() { m_profilesWidget->importFromMRemoteNG(); });
     connect(quitAction, &QAction::triggered, this, []() { qApp->quit(); });
 
     QMenu* helpMenu = menuBar()->addMenu(QStringLiteral("Help"));
@@ -272,6 +306,13 @@ void SessionWindow::addSessionTab(const Profile& profile)
                 m_preferences.eventsPanelExpanded = expanded;
                 saveUiPreferences();
             });
+    connect(tab,
+            &SessionTab::vncScaleModeChanged,
+            this,
+            [this](bool scaleToFit) {
+                m_preferences.vncScaleToFit = scaleToFit;
+                saveUiPreferences();
+            });
 }
 
 void SessionWindow::updateTabTitle(SessionTab* tab, const QString& title)
@@ -303,6 +344,8 @@ void SessionWindow::loadUiPreferences()
         settings.value(QStringLiteral("session/eventsPanelExpanded"), false).toBool();
     m_preferences.terminalFontPointSize =
         settings.value(QStringLiteral("session/terminalFontPointSize"), 0).toInt();
+    m_preferences.vncScaleToFit =
+        settings.value(QStringLiteral("session/vncScaleToFit"), true).toBool();
 }
 
 void SessionWindow::saveUiPreferences() const
@@ -314,4 +357,5 @@ void SessionWindow::saveUiPreferences() const
                       m_preferences.eventsPanelExpanded);
     settings.setValue(QStringLiteral("session/terminalFontPointSize"),
                       m_preferences.terminalFontPointSize);
+    settings.setValue(QStringLiteral("session/vncScaleToFit"), m_preferences.vncScaleToFit);
 }

src/ssh_session_backend.cpp

@@ -7,16 +7,14 @@
 #include <QTextStream>
 #include <QUuid>
 
-namespace {
+SshSessionBackend::SshSessionBackend(const Profile& profile, QObject* parent)
-QString escapeForShellSingleQuotes(const QString& value)
+    : SshSessionBackend(profile, QStringLiteral("ssh"), parent)
 {
-    QString escaped = value;
-    escaped.replace(QStringLiteral("'"), QStringLiteral("'\"'\"'"));
-    return escaped;
-}
 }
 
-SshSessionBackend::SshSessionBackend(const Profile& profile, QObject* parent)
+SshSessionBackend::SshSessionBackend(const Profile& profile,
+                                     const QString& sshProgramOverride,
+                                     QObject* parent)
     : SessionBackend(profile, parent),
       m_process(new QProcess(this)),
       m_connectedProbeTimer(new QTimer(this)),
@@ -27,7 +25,8 @@ SshSessionBackend::SshSessionBackend(const Profile& profile, QObject* parent)
       m_waitingForHostKeyConfirmation(false),
       m_passwordSubmitted(false),
       m_terminalColumns(0),
-      m_terminalRows(0)
+      m_terminalRows(0),
+      m_sshProgram(sshProgramOverride)
 {
     m_connectedProbeTimer->setSingleShot(true);
 
@@ -395,7 +394,7 @@ bool SshSessionBackend::startSshProcess(const SessionConnectOptions& options)
     args << target;
 
     m_process->setProcessEnvironment(environment);
-    m_process->setProgram(QStringLiteral("ssh"));
+    m_process->setProgram(m_sshProgram);
     m_process->setArguments(args);
     m_process->setProcessChannelMode(QProcess::SeparateChannels);
 
@@ -471,7 +470,7 @@ void SshSessionBackend::cleanupAskPassScript()
     }
 }
 
-QString SshSessionBackend::mapSshError(const QString& rawError) const
+QString SshSessionBackend::mapSshError(const QString& rawError)
 {
     const QString raw = rawError.trimmed();
     if (raw.contains(QStringLiteral("Permission denied"), Qt::CaseInsensitive)) {
@@ -510,6 +509,13 @@ QString SshSessionBackend::mapSshError(const QString& rawError) const
     return QStringLiteral("SSH connection failed.");
 }
 
+QString SshSessionBackend::escapeForShellSingleQuotes(const QString& value)
+{
+    QString escaped = value;
+    escaped.replace(QStringLiteral("'"), QStringLiteral("'\"'\"'"));
+    return escaped;
+}
+
 QString SshSessionBackend::knownHostsFileForNullDevice() const
 {
 #ifdef Q_OS_WIN

src/ssh_session_backend.h

@@ -13,8 +13,16 @@ class SshSessionBackend : public SessionBackend
 
 public:
     explicit SshSessionBackend(const Profile& profile, QObject* parent = nullptr);
+    // Test-only: overrides the executable launched instead of "ssh", so
+    // tests can point it at a controllable fixture script.
+    SshSessionBackend(const Profile& profile, const QString& sshProgramOverride, QObject* parent);
     ~SshSessionBackend() override;
 
+    // Pure, state-free helpers exposed as public statics purely so tests
+    // can exercise them directly without spinning up a real ssh process.
+    static QString mapSshError(const QString& rawError);
+    static QString escapeForShellSingleQuotes(const QString& value);
+
 public slots:
     void connectSession(const SessionConnectOptions& options) override;
     void disconnectSession() override;
@@ -46,6 +54,7 @@ private:
     bool m_passwordSubmitted;
     int m_terminalColumns;
     int m_terminalRows;
+    QString m_sshProgram;
 
     void setState(SessionState state, const QString& message);
     bool startSshProcess(const SessionConnectOptions& options);
@@ -53,7 +62,6 @@ private:
                           QProcessEnvironment& environment,
                           QString& error);
     void cleanupAskPassScript();
-    QString mapSshError(const QString& rawError) const;
     QString knownHostsFileForNullDevice() const;
     void applyTerminalSizeIfAvailable();
 };

src/vnc_apple_dh_auth.cpp

@@ -0,0 +1,219 @@
+#include "vnc_apple_dh_auth.h"
+
+#include <openssl/bn.h>
+#include <openssl/core_names.h>
+#include <openssl/evp.h>
+#include <openssl/param_build.h>
+
+#include <cstring>
+#include <memory>
+
+namespace VncAppleDhAuth {
+
+namespace {
+
+struct EvpPkeyDeleter {
+    void operator()(EVP_PKEY* key) const { EVP_PKEY_free(key); }
+};
+struct EvpPkeyCtxDeleter {
+    void operator()(EVP_PKEY_CTX* ctx) const { EVP_PKEY_CTX_free(ctx); }
+};
+struct BnDeleter {
+    void operator()(BIGNUM* bn) const { BN_free(bn); }
+};
+struct ParamBldDeleter {
+    void operator()(OSSL_PARAM_BLD* bld) const { OSSL_PARAM_BLD_free(bld); }
+};
+struct ParamDeleter {
+    void operator()(OSSL_PARAM* params) const { OSSL_PARAM_free(params); }
+};
+struct CipherCtxDeleter {
+    void operator()(EVP_CIPHER_CTX* ctx) const { EVP_CIPHER_CTX_free(ctx); }
+};
+
+using EvpPkeyPtr = std::unique_ptr<EVP_PKEY, EvpPkeyDeleter>;
+using EvpPkeyCtxPtr = std::unique_ptr<EVP_PKEY_CTX, EvpPkeyCtxDeleter>;
+using BnPtr = std::unique_ptr<BIGNUM, BnDeleter>;
+using ParamBldPtr = std::unique_ptr<OSSL_PARAM_BLD, ParamBldDeleter>;
+using ParamPtr = std::unique_ptr<OSSL_PARAM, ParamDeleter>;
+using CipherCtxPtr = std::unique_ptr<EVP_CIPHER_CTX, CipherCtxDeleter>;
+
+BnPtr bnFromBytes(const QByteArray& bytes)
+{
+    return BnPtr(
+        BN_bin2bn(reinterpret_cast<const unsigned char*>(bytes.constData()), bytes.size(), nullptr));
+}
+
+// Builds an EVP_PKEY holding just the DH domain parameters (generator,
+// prime) -- used both as the basis for our own keygen and, with a public
+// value added, to represent the server's public key for derive().
+EvpPkeyPtr buildDomainParams(const BIGNUM* g, const BIGNUM* p)
+{
+    ParamBldPtr bld(OSSL_PARAM_BLD_new());
+    if (!bld) {
+        return nullptr;
+    }
+    if (OSSL_PARAM_BLD_push_BN(bld.get(), OSSL_PKEY_PARAM_FFC_P, p) <= 0
+        || OSSL_PARAM_BLD_push_BN(bld.get(), OSSL_PKEY_PARAM_FFC_G, g) <= 0) {
+        return nullptr;
+    }
+    ParamPtr params(OSSL_PARAM_BLD_to_param(bld.get()));
+    if (!params) {
+        return nullptr;
+    }
+
+    EvpPkeyCtxPtr ctx(EVP_PKEY_CTX_new_from_name(nullptr, "DH", nullptr));
+    if (!ctx || EVP_PKEY_fromdata_init(ctx.get()) <= 0) {
+        return nullptr;
+    }
+    EVP_PKEY* rawKey = nullptr;
+    if (EVP_PKEY_fromdata(ctx.get(), &rawKey, EVP_PKEY_KEY_PARAMETERS, params.get()) <= 0) {
+        return nullptr;
+    }
+    return EvpPkeyPtr(rawKey);
+}
+
+EvpPkeyPtr buildPeerPublicKey(const BIGNUM* g, const BIGNUM* p, const BIGNUM* pub)
+{
+    ParamBldPtr bld(OSSL_PARAM_BLD_new());
+    if (!bld) {
+        return nullptr;
+    }
+    if (OSSL_PARAM_BLD_push_BN(bld.get(), OSSL_PKEY_PARAM_FFC_P, p) <= 0
+        || OSSL_PARAM_BLD_push_BN(bld.get(), OSSL_PKEY_PARAM_FFC_G, g) <= 0
+        || OSSL_PARAM_BLD_push_BN(bld.get(), OSSL_PKEY_PARAM_PUB_KEY, pub) <= 0) {
+        return nullptr;
+    }
+    ParamPtr params(OSSL_PARAM_BLD_to_param(bld.get()));
+    if (!params) {
+        return nullptr;
+    }
+
+    EvpPkeyCtxPtr ctx(EVP_PKEY_CTX_new_from_name(nullptr, "DH", nullptr));
+    if (!ctx || EVP_PKEY_fromdata_init(ctx.get()) <= 0) {
+        return nullptr;
+    }
+    EVP_PKEY* rawKey = nullptr;
+    if (EVP_PKEY_fromdata(ctx.get(), &rawKey, EVP_PKEY_PUBLIC_KEY, params.get()) <= 0) {
+        return nullptr;
+    }
+    return EvpPkeyPtr(rawKey);
+}
+
+}
+
+Response computeResponse(const QByteArray& generator, const QByteArray& prime,
+                         const QByteArray& serverPublicKey, const QString& username,
+                         const QString& password)
+{
+    Response response;
+    if (generator.isEmpty() || prime.isEmpty() || serverPublicKey.isEmpty()) {
+        return response;
+    }
+
+    BnPtr g = bnFromBytes(generator);
+    BnPtr p = bnFromBytes(prime);
+    BnPtr serverPub = bnFromBytes(serverPublicKey);
+    if (!g || !p || !serverPub) {
+        return response;
+    }
+
+    EvpPkeyPtr domainParams = buildDomainParams(g.get(), p.get());
+    if (!domainParams) {
+        return response;
+    }
+
+    // Generate our own ephemeral DH keypair against the same domain
+    // parameters the server offered.
+    EvpPkeyCtxPtr keygenCtx(EVP_PKEY_CTX_new_from_pkey(nullptr, domainParams.get(), nullptr));
+    if (!keygenCtx || EVP_PKEY_keygen_init(keygenCtx.get()) <= 0) {
+        return response;
+    }
+    EVP_PKEY* rawOurKey = nullptr;
+    if (EVP_PKEY_keygen(keygenCtx.get(), &rawOurKey) <= 0) {
+        return response;
+    }
+    EvpPkeyPtr ourKey(rawOurKey);
+
+    BIGNUM* ourPubRaw = nullptr;
+    if (EVP_PKEY_get_bn_param(ourKey.get(), OSSL_PKEY_PARAM_PUB_KEY, &ourPubRaw) <= 0
+        || ourPubRaw == nullptr) {
+        return response;
+    }
+    BnPtr ourPub(ourPubRaw);
+
+    QByteArray clientPublicKey(prime.size(), char(0));
+    if (BN_bn2binpad(ourPub.get(), reinterpret_cast<unsigned char*>(clientPublicKey.data()),
+                     prime.size())
+        < 0) {
+        return response;
+    }
+
+    EvpPkeyPtr peerKey = buildPeerPublicKey(g.get(), p.get(), serverPub.get());
+    if (!peerKey) {
+        return response;
+    }
+
+    EvpPkeyCtxPtr deriveCtx(EVP_PKEY_CTX_new_from_pkey(nullptr, ourKey.get(), nullptr));
+    if (!deriveCtx || EVP_PKEY_derive_init(deriveCtx.get()) <= 0
+        || EVP_PKEY_derive_set_peer(deriveCtx.get(), peerKey.get()) <= 0) {
+        return response;
+    }
+
+    size_t secretLen = 0;
+    if (EVP_PKEY_derive(deriveCtx.get(), nullptr, &secretLen) <= 0 || secretLen == 0) {
+        return response;
+    }
+    QByteArray secret(static_cast<int>(secretLen), char(0));
+    if (EVP_PKEY_derive(deriveCtx.get(), reinterpret_cast<unsigned char*>(secret.data()),
+                        &secretLen)
+        <= 0) {
+        return response;
+    }
+    secret.resize(static_cast<int>(secretLen));
+
+    unsigned char aesKey[16];
+    if (EVP_Digest(secret.constData(), static_cast<size_t>(secret.size()), aesKey, nullptr,
+                   EVP_md5(), nullptr)
+        <= 0) {
+        return response;
+    }
+
+    // 64 bytes username + 64 bytes password, NUL-padded/truncated.
+    QByteArray credentials(128, char(0));
+    const QByteArray userBytes = username.toLatin1().left(64);
+    const QByteArray passBytes = password.toLatin1().left(64);
+    std::memcpy(credentials.data(), userBytes.constData(),
+               static_cast<size_t>(userBytes.size()));
+    std::memcpy(credentials.data() + 64, passBytes.constData(),
+               static_cast<size_t>(passBytes.size()));
+
+    CipherCtxPtr cipherCtx(EVP_CIPHER_CTX_new());
+    if (!cipherCtx
+        || EVP_EncryptInit_ex(cipherCtx.get(), EVP_aes_128_ecb(), nullptr, aesKey, nullptr) <= 0) {
+        return response;
+    }
+    EVP_CIPHER_CTX_set_padding(cipherCtx.get(), 0);
+
+    QByteArray ciphertext(credentials.size() + EVP_MAX_BLOCK_LENGTH, char(0));
+    int outLen1 = 0;
+    if (EVP_EncryptUpdate(cipherCtx.get(), reinterpret_cast<unsigned char*>(ciphertext.data()),
+                          &outLen1, reinterpret_cast<const unsigned char*>(credentials.constData()),
+                          credentials.size())
+        <= 0) {
+        return response;
+    }
+    int outLen2 = 0;
+    if (EVP_EncryptFinal_ex(cipherCtx.get(),
+                            reinterpret_cast<unsigned char*>(ciphertext.data()) + outLen1, &outLen2)
+        <= 0) {
+        return response;
+    }
+    ciphertext.resize(outLen1 + outLen2);
+
+    response.clientPublicKey = clientPublicKey;
+    response.encryptedCredentials = ciphertext;
+    return response;
+}
+
+}

src/vnc_apple_dh_auth.h

@@ -0,0 +1,44 @@
+#ifndef ORBITHUB_VNC_APPLE_DH_AUTH_H
+#define ORBITHUB_VNC_APPLE_DH_AUTH_H
+
+#include <QByteArray>
+#include <QString>
+
+// Apple's Screen Sharing authentication scheme (RFB security type 30):
+// Diffie-Hellman key exchange followed by AES-128-ECB-encrypted
+// credentials. Apple never published this officially -- it's not part of
+// RFC 6143 -- so this implements the well-established reverse-engineered
+// wire format used by several independent VNC clients, not a primary
+// spec. Kept as a pure, state-free helper (no socket access) so it's
+// unit-testable without a live connection, mirroring
+// VncSessionBackend::vncAuthResponse()'s shape for standard VNC
+// Authentication.
+namespace VncAppleDhAuth {
+
+struct Response {
+    // Same byte length as the server's prime, big-endian, zero-padded.
+    // Empty on any failure (malformed input, an OpenSSL operation
+    // failing) -- callers should treat an empty clientPublicKey as "could
+    // not compute a response" rather than send a degenerate one.
+    QByteArray clientPublicKey;
+    // Always exactly 128 bytes on success (16 AES blocks): a 64-byte
+    // NUL-padded/truncated username followed by a 64-byte NUL-padded/
+    // truncated password, AES-128-ECB encrypted (no padding, since the
+    // plaintext is already an exact multiple of the block size) with a
+    // key derived as MD5(sharedSecret).
+    QByteArray encryptedCredentials;
+};
+
+// Computes the DH keypair, the shared secret, the derived AES key, and
+// the encrypted credential blob, using modern EVP-based OpenSSL 3.0 APIs
+// throughout (no deprecated low-level DH_*/legacy calls -- unlike VNC
+// Authentication's classic DES usage, none of MD5/AES-ECB/the EVP_PKEY DH
+// APIs are deprecated, so no compatibility pragma is needed here).
+// Returns a Response with an empty clientPublicKey on any failure.
+Response computeResponse(const QByteArray& generator, const QByteArray& prime,
+                         const QByteArray& serverPublicKey, const QString& username,
+                         const QString& password);
+
+}
+
+#endif

src/vnc_apple_rsa_auth.cpp

@@ -0,0 +1,118 @@
+#include "vnc_apple_rsa_auth.h"
+
+#include <openssl/evp.h>
+#include <openssl/rand.h>
+#include <openssl/rsa.h>
+#include <openssl/x509.h>
+
+#include <memory>
+
+namespace VncAppleRsaAuth {
+
+namespace {
+
+struct EvpPkeyDeleter {
+    void operator()(EVP_PKEY* key) const { EVP_PKEY_free(key); }
+};
+struct EvpPkeyCtxDeleter {
+    void operator()(EVP_PKEY_CTX* ctx) const { EVP_PKEY_CTX_free(ctx); }
+};
+struct CipherCtxDeleter {
+    void operator()(EVP_CIPHER_CTX* ctx) const { EVP_CIPHER_CTX_free(ctx); }
+};
+
+using EvpPkeyPtr = std::unique_ptr<EVP_PKEY, EvpPkeyDeleter>;
+using EvpPkeyCtxPtr = std::unique_ptr<EVP_PKEY_CTX, EvpPkeyCtxDeleter>;
+using CipherCtxPtr = std::unique_ptr<EVP_CIPHER_CTX, CipherCtxDeleter>;
+
+}
+
+QByteArray packCredential(const QString& text)
+{
+    QByteArray data = text.toUtf8();
+    data.append(char(0));
+    if (data.size() < 64) {
+        QByteArray padding(64 - data.size(), char(0));
+        // Best-effort: if RAND_bytes fails, zero-padding is still
+        // correct (the NUL terminator above already unambiguously marks
+        // the string's real end for the server) -- only the ECB-pattern-
+        // hiding benefit of random padding is lost, not correctness.
+        RAND_bytes(reinterpret_cast<unsigned char*>(padding.data()), padding.size());
+        data += padding;
+    } else {
+        data = data.left(64);
+    }
+    return data;
+}
+
+Response computeResponse(const QByteArray& hostKeyDer, const QString& username,
+                         const QString& password)
+{
+    Response response;
+    if (hostKeyDer.isEmpty()) {
+        return response;
+    }
+
+    const auto* derPtr = reinterpret_cast<const unsigned char*>(hostKeyDer.constData());
+    EvpPkeyPtr hostKey(d2i_PUBKEY(nullptr, &derPtr, hostKeyDer.size()));
+    if (!hostKey) {
+        return response;
+    }
+
+    unsigned char aesKeyBytes[16];
+    if (RAND_bytes(aesKeyBytes, sizeof(aesKeyBytes)) != 1) {
+        return response;
+    }
+
+    const QByteArray credentials = packCredential(username) + packCredential(password);
+
+    CipherCtxPtr cipherCtx(EVP_CIPHER_CTX_new());
+    if (!cipherCtx
+        || EVP_EncryptInit_ex(cipherCtx.get(), EVP_aes_128_ecb(), nullptr, aesKeyBytes, nullptr)
+               <= 0) {
+        return response;
+    }
+    EVP_CIPHER_CTX_set_padding(cipherCtx.get(), 0);
+
+    QByteArray encryptedCredentials(credentials.size() + EVP_MAX_BLOCK_LENGTH, char(0));
+    int outLen1 = 0;
+    if (EVP_EncryptUpdate(cipherCtx.get(),
+                          reinterpret_cast<unsigned char*>(encryptedCredentials.data()), &outLen1,
+                          reinterpret_cast<const unsigned char*>(credentials.constData()),
+                          credentials.size())
+        <= 0) {
+        return response;
+    }
+    int outLen2 = 0;
+    if (EVP_EncryptFinal_ex(cipherCtx.get(),
+                            reinterpret_cast<unsigned char*>(encryptedCredentials.data()) + outLen1,
+                            &outLen2)
+        <= 0) {
+        return response;
+    }
+    encryptedCredentials.resize(outLen1 + outLen2);
+
+    EvpPkeyCtxPtr rsaCtx(EVP_PKEY_CTX_new(hostKey.get(), nullptr));
+    if (!rsaCtx || EVP_PKEY_encrypt_init(rsaCtx.get()) <= 0
+        || EVP_PKEY_CTX_set_rsa_padding(rsaCtx.get(), RSA_PKCS1_PADDING) <= 0) {
+        return response;
+    }
+    size_t encryptedKeyLen = 0;
+    if (EVP_PKEY_encrypt(rsaCtx.get(), nullptr, &encryptedKeyLen, aesKeyBytes, sizeof(aesKeyBytes))
+        <= 0) {
+        return response;
+    }
+    QByteArray encryptedAesKey(static_cast<int>(encryptedKeyLen), char(0));
+    if (EVP_PKEY_encrypt(rsaCtx.get(), reinterpret_cast<unsigned char*>(encryptedAesKey.data()),
+                         &encryptedKeyLen, aesKeyBytes, sizeof(aesKeyBytes))
+        <= 0) {
+        return response;
+    }
+    encryptedAesKey.resize(static_cast<int>(encryptedKeyLen));
+
+    response.encryptedCredentials = encryptedCredentials;
+    response.encryptedAesKey = encryptedAesKey;
+    return response;
+}
+
+}

src/vnc_apple_rsa_auth.h

@@ -0,0 +1,51 @@
+#ifndef ORBITHUB_VNC_APPLE_RSA_AUTH_H
+#define ORBITHUB_VNC_APPLE_RSA_AUTH_H
+
+#include <QByteArray>
+#include <QString>
+
+// Apple Screen Sharing's RSA-based authentication scheme (RFB security
+// type 33, sometimes called "MacAuthentication" or "ARD authentication").
+// Distinct from security type 30 (Diffie-Hellman + AES, see
+// vnc_apple_dh_auth.h): modern macOS advertises both, but empirically only
+// type 33 is actually functional -- type 30 appears to be vestigial.
+// Neither is part of RFC 6143; this wire format and crypto shape was
+// confirmed against the `asyncvnc` PyPI package's implementation (a real,
+// working, independently-maintained VNC client) rather than derived from
+// official Apple documentation, which doesn't exist for this scheme.
+//
+// Scheme: the server hands the client its RSA public key (DER-encoded
+// X.509 SubjectPublicKeyInfo); the client generates a random AES-128 key,
+// encrypts the username+password with it, then RSA-PKCS1v1.5-encrypts
+// that AES key with the server's public key and sends both back.
+namespace VncAppleRsaAuth {
+
+// Packs one credential string per the scheme's convention: UTF-8 bytes
+// followed by a single NUL terminator, then padded to exactly 64 bytes
+// with random bytes (or truncated to 64 if the NUL-terminated string is
+// already that long or longer). The NUL terminator is what lets the
+// server find the string's real end despite the random padding -- the
+// padding's specific value isn't otherwise significant. Exposed publicly
+// so it's independently unit-testable.
+QByteArray packCredential(const QString& text);
+
+struct Response {
+    // Exactly 128 bytes on success (packCredential(username) +
+    // packCredential(password), AES-128-ECB encrypted). Empty on failure.
+    QByteArray encryptedCredentials;
+    // RSA-modulus-length bytes on success (the random AES key,
+    // PKCS1v1.5-encrypted with the server's public key). Empty on
+    // failure.
+    QByteArray encryptedAesKey;
+};
+
+// Computes the full type-33 response from the server's DER-encoded RSA
+// public key and the credentials to authenticate with. Returns a Response
+// with both fields empty on any failure (malformed key, an OpenSSL
+// operation failing).
+Response computeResponse(const QByteArray& hostKeyDer, const QString& username,
+                         const QString& password);
+
+}
+
+#endif

src/vnc_display_widget.cpp

@@ -0,0 +1,350 @@
+#include "vnc_display_widget.h"
+
+#include <QCursor>
+#include <QEvent>
+#include <QKeyEvent>
+#include <QMouseEvent>
+#include <QPainter>
+#include <QPixmap>
+#include <QResizeEvent>
+#include <QTimer>
+#include <QWheelEvent>
+#include <QtGlobal>
+
+namespace {
+QSize sanitizeSize(const QSize& size)
+{
+    return QSize(qMax(1, size.width()), qMax(1, size.height()));
+}
+
+qreal sanitizeDevicePixelRatio(qreal ratio)
+{
+    if (!(ratio > 0.0)) {
+        return 1.0;
+    }
+    return qBound(1.0, ratio, 4.0);
+}
+
+constexpr int kResizeDebounceMs = 150;
+}
+
+VncDisplayWidget::VncDisplayWidget(QWidget* parent)
+    : QWidget(parent),
+      m_remoteSize(1280, 720),
+      m_resizeDebounceTimer(new QTimer(this)),
+      m_scaleToFit(true),
+      m_cursorMode(CursorMode::Default)
+{
+    setFocusPolicy(Qt::StrongFocus);
+    setMouseTracking(true);
+    setAutoFillBackground(false);
+    setMinimumSize(320, 200);
+
+    m_resizeDebounceTimer->setSingleShot(true);
+    connect(m_resizeDebounceTimer, &QTimer::timeout, this, &VncDisplayWidget::emitViewportGeometry);
+
+    scheduleViewportGeometryEmit();
+}
+
+void VncDisplayWidget::setFrame(const QImage& frame)
+{
+    if (frame.isNull()) {
+        return;
+    }
+
+    m_frame = frame;
+    m_remoteSize = sanitizeSize(frame.size());
+    applySizeConstraint();
+    update();
+}
+
+void VncDisplayWidget::setRemoteDesktopSize(int width, int height)
+{
+    if (width < 1 || height < 1) {
+        return;
+    }
+
+    const QSize nextSize(width, height);
+    if (m_remoteSize == nextSize) {
+        return;
+    }
+
+    m_remoteSize = nextSize;
+    // Same race guarded against as RdpDisplayWidget: the next actual frame
+    // arrives asynchronously and isn't guaranteed to already match this
+    // size, so drop the stale one rather than stretch it by the wrong
+    // factor until a correctly-sized frame lands.
+    m_frame = QImage();
+    applySizeConstraint();
+    update();
+}
+
+void VncDisplayWidget::setScaleToFit(bool scaleToFit)
+{
+    if (m_scaleToFit == scaleToFit) {
+        return;
+    }
+    m_scaleToFit = scaleToFit;
+    applySizeConstraint();
+    applyCursor();
+    update();
+}
+
+void VncDisplayWidget::applySizeConstraint()
+{
+    if (m_scaleToFit) {
+        // Let the widget follow whatever it's placed in again (e.g. a
+        // QScrollArea in resizable mode, or a plain layout).
+        setMinimumSize(320, 200);
+        setMaximumSize(QWIDGETSIZE_MAX, QWIDGETSIZE_MAX);
+    } else {
+        // Fixed at the remote's actual pixel size. renderRect()'s
+        // scale-to-fit math naturally degenerates to an unscaled 1:1
+        // mapping once the widget's own bounds already equal the remote
+        // size, so no separate "actual size" rendering path is needed --
+        // this is the only thing that differs between the two modes.
+        setFixedSize(effectiveRemoteSize());
+    }
+}
+
+void VncDisplayWidget::clearFrame()
+{
+    m_frame = QImage();
+    update();
+}
+
+void VncDisplayWidget::paintEvent(QPaintEvent* event)
+{
+    Q_UNUSED(event);
+
+    QPainter painter(this);
+    painter.fillRect(rect(), QColor(QStringLiteral("#101214")));
+
+    const QRectF target = renderRect();
+    if (!m_frame.isNull()) {
+        painter.drawImage(target, m_frame);
+    } else {
+        painter.setPen(QColor(QStringLiteral("#b0bec5")));
+        painter.drawText(rect(),
+                         Qt::AlignCenter,
+                         QStringLiteral("Waiting for remote desktop frame..."));
+    }
+}
+
+void VncDisplayWidget::resizeEvent(QResizeEvent* event)
+{
+    QWidget::resizeEvent(event);
+    scheduleViewportGeometryEmit();
+    applyCursor();
+}
+
+bool VncDisplayWidget::event(QEvent* event)
+{
+    if (event->type() == QEvent::ScreenChangeInternal) {
+        scheduleViewportGeometryEmit();
+    }
+    return QWidget::event(event);
+}
+
+void VncDisplayWidget::scheduleViewportGeometryEmit()
+{
+    m_resizeDebounceTimer->start(kResizeDebounceMs);
+}
+
+void VncDisplayWidget::emitViewportGeometry()
+{
+    const QSize logicalSize = sanitizeSize(this->size());
+    const qreal ratio = sanitizeDevicePixelRatio(this->devicePixelRatioF());
+    const QSize physicalSize(qRound(logicalSize.width() * ratio), qRound(logicalSize.height() * ratio));
+    emit viewportSizeChanged(physicalSize.width(), physicalSize.height());
+    emit displayScaleChanged(ratio);
+}
+
+void VncDisplayWidget::keyPressEvent(QKeyEvent* event)
+{
+    if (event == nullptr) {
+        return;
+    }
+
+    emit keyInput(event->key(),
+                  event->nativeScanCode(),
+                  event->text(),
+                  true,
+                  static_cast<int>(event->modifiers()));
+    event->accept();
+}
+
+void VncDisplayWidget::keyReleaseEvent(QKeyEvent* event)
+{
+    if (event == nullptr || event->isAutoRepeat()) {
+        return;
+    }
+
+    emit keyInput(event->key(),
+                  event->nativeScanCode(),
+                  event->text(),
+                  false,
+                  static_cast<int>(event->modifiers()));
+    event->accept();
+}
+
+bool VncDisplayWidget::focusNextPrevChild(bool next)
+{
+    Q_UNUSED(next);
+    // Tab/Shift+Tab must reach keyPressEvent() and be forwarded to the
+    // remote session instead of moving focus to the next local widget.
+    return false;
+}
+
+void VncDisplayWidget::mousePressEvent(QMouseEvent* event)
+{
+    if (event == nullptr) {
+        return;
+    }
+
+    setFocus(Qt::MouseFocusReason);
+    const QPoint mapped = mapToRemote(event->position());
+    emit mouseButtonInput(mapped.x(), mapped.y(), static_cast<int>(event->button()), true);
+    event->accept();
+}
+
+void VncDisplayWidget::mouseReleaseEvent(QMouseEvent* event)
+{
+    if (event == nullptr) {
+        return;
+    }
+
+    const QPoint mapped = mapToRemote(event->position());
+    emit mouseButtonInput(mapped.x(), mapped.y(), static_cast<int>(event->button()), false);
+    event->accept();
+}
+
+void VncDisplayWidget::mouseMoveEvent(QMouseEvent* event)
+{
+    if (event == nullptr) {
+        return;
+    }
+
+    const QPoint mapped = mapToRemote(event->position());
+    emit mouseMoveInput(mapped.x(), mapped.y());
+    event->accept();
+}
+
+void VncDisplayWidget::wheelEvent(QWheelEvent* event)
+{
+    if (event == nullptr) {
+        return;
+    }
+
+    const QPoint mapped = mapToRemote(event->position());
+    const QPoint angle = event->angleDelta();
+    emit mouseWheelInput(mapped.x(), mapped.y(), angle.x(), angle.y());
+    event->accept();
+}
+
+QRectF VncDisplayWidget::renderRect() const
+{
+    const QSize remote = effectiveRemoteSize();
+    const QRectF area = rect();
+    if (area.isEmpty()) {
+        return QRectF();
+    }
+
+    const qreal scale = qMin(area.width() / remote.width(), area.height() / remote.height());
+    const qreal drawWidth = remote.width() * scale;
+    const qreal drawHeight = remote.height() * scale;
+    const qreal x = area.x() + ((area.width() - drawWidth) * 0.5);
+    const qreal y = area.y() + ((area.height() - drawHeight) * 0.5);
+    return QRectF(x, y, drawWidth, drawHeight);
+}
+
+QPoint VncDisplayWidget::mapToRemote(const QPointF& pos) const
+{
+    const QSize remote = effectiveRemoteSize();
+    const QRectF target = renderRect();
+    if (target.isEmpty()) {
+        return QPoint(0, 0);
+    }
+
+    const qreal clampedX = qBound(target.left(), pos.x(), target.right());
+    const qreal clampedY = qBound(target.top(), pos.y(), target.bottom());
+
+    const qreal normalizedX = (clampedX - target.left()) / qMax(1.0, target.width());
+    const qreal normalizedY = (clampedY - target.top()) / qMax(1.0, target.height());
+
+    const int remoteX = qBound(0, static_cast<int>(normalizedX * remote.width()), remote.width() - 1);
+    const int remoteY = qBound(0, static_cast<int>(normalizedY * remote.height()), remote.height() - 1);
+    return QPoint(remoteX, remoteY);
+}
+
+QSize VncDisplayWidget::effectiveRemoteSize() const
+{
+    if (m_remoteSize.width() > 0 && m_remoteSize.height() > 0) {
+        return m_remoteSize;
+    }
+    if (!m_frame.isNull()) {
+        return sanitizeSize(m_frame.size());
+    }
+    return QSize(1280, 720);
+}
+
+void VncDisplayWidget::setCursorImage(const QImage& image, const QPoint& hotspot)
+{
+    m_cursorImage = image;
+    m_cursorHotspot = hotspot;
+    m_cursorMode = CursorMode::Custom;
+    applyCursor();
+}
+
+void VncDisplayWidget::setCursorHidden()
+{
+    m_cursorMode = CursorMode::Hidden;
+    applyCursor();
+}
+
+void VncDisplayWidget::setCursorDefault()
+{
+    m_cursorMode = CursorMode::Default;
+    applyCursor();
+}
+
+void VncDisplayWidget::applyCursor()
+{
+    if (m_cursorMode == CursorMode::Hidden) {
+        setCursor(Qt::BlankCursor);
+        return;
+    }
+
+    if (m_cursorMode == CursorMode::Default || m_cursorImage.isNull()) {
+        unsetCursor();
+        return;
+    }
+
+    // renderRect()/effectiveRemoteSize() already account for both display
+    // modes: in actual-size mode the scale factor naturally comes out to
+    // 1.0 (see applySizeConstraint()'s comment), so no special-casing is
+    // needed here beyond reusing the same geometry helpers RDP's version
+    // uses for its single (always scale-to-fit) mode.
+    const QSize remote = effectiveRemoteSize();
+    const QRectF target = renderRect();
+    if (remote.isEmpty() || target.isEmpty()) {
+        setCursor(QCursor(QPixmap::fromImage(m_cursorImage),
+                          m_cursorHotspot.x(),
+                          m_cursorHotspot.y()));
+        return;
+    }
+
+    const qreal scale = target.width() / remote.width();
+    QImage scaledImage = m_cursorImage;
+    if (!qFuzzyCompare(scale, 1.0)) {
+        scaledImage = m_cursorImage.scaled(
+            qMax(1, qRound(m_cursorImage.width() * scale)),
+            qMax(1, qRound(m_cursorImage.height() * scale)),
+            Qt::IgnoreAspectRatio,
+            Qt::SmoothTransformation);
+    }
+
+    const int hotX = qBound(0, qRound(m_cursorHotspot.x() * scale), scaledImage.width());
+    const int hotY = qBound(0, qRound(m_cursorHotspot.y() * scale), scaledImage.height());
+    setCursor(QCursor(QPixmap::fromImage(scaledImage), hotX, hotY));
+}

src/vnc_display_widget.h

@@ -0,0 +1,94 @@
+#ifndef ORBITHUB_VNC_DISPLAY_WIDGET_H
+#define ORBITHUB_VNC_DISPLAY_WIDGET_H
+
+#include <QImage>
+#include <QPoint>
+#include <QWidget>
+
+class QKeyEvent;
+class QMouseEvent;
+class QPaintEvent;
+class QResizeEvent;
+class QTimer;
+class QWheelEvent;
+
+// Renders a VNC framebuffer and forwards local input, scaled-to-fit --
+// same shape as RdpDisplayWidget, including remote cursor-shape sync.
+class VncDisplayWidget : public QWidget
+{
+    Q_OBJECT
+
+public:
+    explicit VncDisplayWidget(QWidget* parent = nullptr);
+
+    void setFrame(const QImage& frame);
+    void setRemoteDesktopSize(int width, int height);
+    void clearFrame();
+
+    // true (default): scale the whole remote screen to fit the widget,
+    // like RdpDisplayWidget. false: render at the remote's actual pixel
+    // size -- meant to be placed inside a QScrollArea, whose scrollbars
+    // then let the user pan around a screen larger than the window
+    // instead of shrinking small text to illegibility. VNC has no
+    // equivalent of RDP's MS-RDPEDISP to request a different resolution
+    // from the guest, so this is the only way to see it at native size.
+    void setScaleToFit(bool scaleToFit);
+    bool scaleToFit() const
+    {
+        return m_scaleToFit;
+    }
+
+    // Mirrors RdpDisplayWidget's cursor handling. VNC's Cursor pseudo-
+    // encoding never signals "reset to default" the way RDP's SetDefault
+    // callback does -- it only ever supplies a shape or hides the cursor --
+    // so setCursorDefault() exists for symmetry/future use but VNC sessions
+    // never call it today.
+    void setCursorImage(const QImage& image, const QPoint& hotspot);
+    void setCursorHidden();
+    void setCursorDefault();
+
+signals:
+    void keyInput(int key, quint32 nativeScanCode, const QString& text, bool pressed, int modifiers);
+    void mouseMoveInput(int x, int y);
+    void mouseButtonInput(int x, int y, int button, bool pressed);
+    void mouseWheelInput(int x, int y, int deltaX, int deltaY);
+    void viewportSizeChanged(int width, int height);
+    void displayScaleChanged(qreal devicePixelRatio);
+
+protected:
+    void paintEvent(QPaintEvent* event) override;
+    void resizeEvent(QResizeEvent* event) override;
+    bool event(QEvent* event) override;
+    void keyPressEvent(QKeyEvent* event) override;
+    void keyReleaseEvent(QKeyEvent* event) override;
+    void mousePressEvent(QMouseEvent* event) override;
+    void mouseReleaseEvent(QMouseEvent* event) override;
+    void mouseMoveEvent(QMouseEvent* event) override;
+    void wheelEvent(QWheelEvent* event) override;
+    bool focusNextPrevChild(bool next) override;
+
+private:
+    enum class CursorMode {
+        Default,
+        Hidden,
+        Custom,
+    };
+
+    QImage m_frame;
+    QSize m_remoteSize;
+    QTimer* m_resizeDebounceTimer;
+    bool m_scaleToFit;
+    QImage m_cursorImage;
+    QPoint m_cursorHotspot;
+    CursorMode m_cursorMode;
+
+    QRectF renderRect() const;
+    QPoint mapToRemote(const QPointF& pos) const;
+    QSize effectiveRemoteSize() const;
+    void emitViewportGeometry();
+    void scheduleViewportGeometryEmit();
+    void applySizeConstraint();
+    void applyCursor();
+};
+
+#endif

src/vnc_pixel_codecs.cpp

@@ -0,0 +1,369 @@
+#include "vnc_pixel_codecs.h"
+
+namespace VncPixelCodecs {
+
+QRgb rgbFromPixelBytes(const uchar* bytes)
+{
+    // Byte order B,G,R,pad -- matches VncSessionBackend's negotiated
+    // SetPixelFormat (32bpp little-endian, R at shift 16 / G at 8 / B at 0).
+    return qRgb(bytes[2], bytes[1], bytes[0]);
+}
+
+int hextileFixedMetaByteCount(quint8 subencoding)
+{
+    int count = 0;
+    if ((subencoding & HextileFlags::kBackgroundSpecified) != 0) {
+        count += 4;
+    }
+    if ((subencoding & HextileFlags::kForegroundSpecified) != 0) {
+        count += 4;
+    }
+    if ((subencoding & HextileFlags::kAnySubrects) != 0) {
+        count += 1;
+    }
+    return count;
+}
+
+int decodeHextileFixedMeta(quint8 subencoding, const QByteArray& data, QRgb* background,
+                           QRgb* foreground)
+{
+    int offset = 0;
+    const auto* bytes = reinterpret_cast<const uchar*>(data.constData());
+
+    if ((subencoding & HextileFlags::kBackgroundSpecified) != 0) {
+        *background = rgbFromPixelBytes(bytes + offset);
+        offset += 4;
+    }
+    if ((subencoding & HextileFlags::kForegroundSpecified) != 0) {
+        *foreground = rgbFromPixelBytes(bytes + offset);
+        offset += 4;
+    }
+    if ((subencoding & HextileFlags::kAnySubrects) != 0) {
+        return static_cast<int>(static_cast<quint8>(data.at(offset)));
+    }
+    return 0;
+}
+
+int hextileSubrectByteCount(bool coloured, int subrectCount)
+{
+    return subrectCount * (coloured ? 6 : 2);
+}
+
+QVector<HextileSubrect> decodeHextileSubrects(bool coloured, int subrectCount,
+                                              const QByteArray& data, QRgb foreground)
+{
+    QVector<HextileSubrect> subrects;
+    subrects.reserve(subrectCount);
+
+    const auto* bytes = reinterpret_cast<const uchar*>(data.constData());
+    const int stride = coloured ? 6 : 2;
+    for (int i = 0; i < subrectCount; ++i) {
+        const uchar* entry = bytes + (i * stride);
+        QRgb color = foreground;
+        int fieldOffset = 0;
+        if (coloured) {
+            color = rgbFromPixelBytes(entry);
+            fieldOffset = 4;
+        }
+        const uchar xy = entry[fieldOffset];
+        const uchar wh = entry[fieldOffset + 1];
+        // High nibble = x (or width-1), low nibble = y (or height-1).
+        const int x = (xy >> 4) & 0x0F;
+        const int y = xy & 0x0F;
+        const int width = ((wh >> 4) & 0x0F) + 1;
+        const int height = (wh & 0x0F) + 1;
+        subrects.append(HextileSubrect{QRect(x, y, width, height), color});
+    }
+    return subrects;
+}
+
+int decodeZrleTile(const QByteArray& data, int offset, int tileWidth, int tileHeight,
+                   QVector<QRgb>& pixels)
+{
+    const int pixelCount = tileWidth * tileHeight;
+    const auto* bytes = reinterpret_cast<const uchar*>(data.constData());
+    const int size = data.size();
+    if (offset < 0 || offset >= size || pixelCount <= 0) {
+        return -1;
+    }
+
+    int pos = offset;
+    const quint8 subencoding = bytes[pos];
+    ++pos;
+
+    // CPIXEL is 3 bytes for our negotiated 32bpp/24-depth true-color
+    // format -- the padding byte a full pixel would have is simply
+    // omitted. rgbFromPixelBytes() already only reads the first 3 bytes it
+    // is given (B,G,R order), so it doubles as the CPIXEL reader.
+    auto readCpixel = [&](QRgb* out) -> bool {
+        if (pos + 3 > size) {
+            return false;
+        }
+        *out = rgbFromPixelBytes(bytes + pos);
+        pos += 3;
+        return true;
+    };
+
+    // Shared continuation-byte run-length reader for both RLE subencoding
+    // families: keep summing bytes while they equal 255, add the final
+    // (non-255) byte, and the true run length is that sum plus one.
+    auto readRunLength = [&](int* out) -> bool {
+        int total = 0;
+        for (;;) {
+            if (pos >= size) {
+                return false;
+            }
+            const quint8 b = bytes[pos];
+            ++pos;
+            total += b;
+            if (b != 255) {
+                break;
+            }
+        }
+        *out = total + 1;
+        return true;
+    };
+
+    if (subencoding == 0) { // Raw
+        pixels.reserve(pixels.size() + pixelCount);
+        for (int i = 0; i < pixelCount; ++i) {
+            QRgb color = 0;
+            if (!readCpixel(&color)) {
+                return -1;
+            }
+            pixels.append(color);
+        }
+        return pos - offset;
+    }
+
+    if (subencoding == 1) { // Solid
+        QRgb color = 0;
+        if (!readCpixel(&color)) {
+            return -1;
+        }
+        pixels.reserve(pixels.size() + pixelCount);
+        for (int i = 0; i < pixelCount; ++i) {
+            pixels.append(color);
+        }
+        return pos - offset;
+    }
+
+    if (subencoding >= 2 && subencoding <= 16) { // Packed palette
+        const int paletteSize = subencoding;
+        QVector<QRgb> palette;
+        palette.reserve(paletteSize);
+        for (int i = 0; i < paletteSize; ++i) {
+            QRgb color = 0;
+            if (!readCpixel(&color)) {
+                return -1;
+            }
+            palette.append(color);
+        }
+
+        int bitsPerPixel = 4;
+        if (paletteSize == 2) {
+            bitsPerPixel = 1;
+        } else if (paletteSize <= 4) {
+            bitsPerPixel = 2;
+        }
+        const int rowBytes = (tileWidth * bitsPerPixel + 7) / 8;
+
+        pixels.reserve(pixels.size() + pixelCount);
+        for (int y = 0; y < tileHeight; ++y) {
+            if (pos + rowBytes > size) {
+                return -1;
+            }
+            int bitPos = 0;
+            for (int x = 0; x < tileWidth; ++x) {
+                const int byteIndex = pos + (bitPos / 8);
+                const int shift = 8 - (bitPos % 8) - bitsPerPixel;
+                const int mask = (1 << bitsPerPixel) - 1;
+                const int index = (bytes[byteIndex] >> shift) & mask;
+                if (index >= palette.size()) {
+                    return -1;
+                }
+                pixels.append(palette.at(index));
+                bitPos += bitsPerPixel;
+            }
+            pos += rowBytes;
+        }
+        return pos - offset;
+    }
+
+    if (subencoding == 128) { // Plain RLE
+        int produced = 0;
+        while (produced < pixelCount) {
+            QRgb color = 0;
+            if (!readCpixel(&color)) {
+                return -1;
+            }
+            int runLength = 0;
+            if (!readRunLength(&runLength)) {
+                return -1;
+            }
+            for (int i = 0; i < runLength && produced < pixelCount; ++i, ++produced) {
+                pixels.append(color);
+            }
+        }
+        return pos - offset;
+    }
+
+    if (subencoding >= 130) { // Palette RLE (129 is unused/invalid, falls through below)
+        const int paletteSize = subencoding - 128;
+        QVector<QRgb> palette;
+        palette.reserve(paletteSize);
+        for (int i = 0; i < paletteSize; ++i) {
+            QRgb color = 0;
+            if (!readCpixel(&color)) {
+                return -1;
+            }
+            palette.append(color);
+        }
+
+        int produced = 0;
+        while (produced < pixelCount) {
+            if (pos >= size) {
+                return -1;
+            }
+            const quint8 indexByte = bytes[pos];
+            ++pos;
+
+            int index = indexByte;
+            int runLength = 1;
+            if (indexByte >= 128) {
+                index = indexByte - 128;
+                if (!readRunLength(&runLength)) {
+                    return -1;
+                }
+            }
+            if (index >= palette.size()) {
+                return -1;
+            }
+            const QRgb color = palette.at(index);
+            for (int i = 0; i < runLength && produced < pixelCount; ++i, ++produced) {
+                pixels.append(color);
+            }
+        }
+        return pos - offset;
+    }
+
+    // Subencodings 17-127 and 129 are not defined by RFC 6143.
+    return -1;
+}
+
+QVector<QRgb> decodeTightCopyFilter(const QByteArray& data, int width, int height)
+{
+    const int pixelCount = width * height;
+    QVector<QRgb> pixels;
+    if (pixelCount <= 0 || data.size() < pixelCount * 3) {
+        return pixels;
+    }
+    pixels.reserve(pixelCount);
+    const auto* bytes = reinterpret_cast<const uchar*>(data.constData());
+    for (int i = 0; i < pixelCount; ++i) {
+        pixels.append(rgbFromPixelBytes(bytes + (i * 3)));
+    }
+    return pixels;
+}
+
+QVector<QRgb> decodeTightPaletteFilter(const QByteArray& data, int width, int height)
+{
+    QVector<QRgb> pixels;
+    const int pixelCount = width * height;
+    if (pixelCount <= 0 || data.isEmpty()) {
+        return pixels;
+    }
+
+    const auto* bytes = reinterpret_cast<const uchar*>(data.constData());
+    const int size = data.size();
+    int pos = 0;
+    const int paletteSize = static_cast<int>(bytes[pos]) + 1; // 1-256 colors
+    ++pos;
+    if (pos + (paletteSize * 3) > size) {
+        return pixels;
+    }
+
+    QVector<QRgb> palette;
+    palette.reserve(paletteSize);
+    for (int i = 0; i < paletteSize; ++i) {
+        palette.append(rgbFromPixelBytes(bytes + pos));
+        pos += 3;
+    }
+
+    int bitsPerPixel = 8;
+    if (paletteSize <= 2) {
+        bitsPerPixel = 1;
+    } else if (paletteSize <= 4) {
+        bitsPerPixel = 2;
+    } else if (paletteSize <= 16) {
+        bitsPerPixel = 4;
+    }
+
+    pixels.reserve(pixelCount);
+    int bitPos = 0;
+    for (int i = 0; i < pixelCount; ++i) {
+        const int byteIndex = pos + (bitPos / 8);
+        if (byteIndex >= size) {
+            return QVector<QRgb>();
+        }
+        const int shift = 8 - (bitPos % 8) - bitsPerPixel;
+        const int mask = (1 << bitsPerPixel) - 1;
+        const int index = (bytes[byteIndex] >> shift) & mask;
+        if (index >= palette.size()) {
+            return QVector<QRgb>();
+        }
+        pixels.append(palette.at(index));
+        bitPos += bitsPerPixel;
+    }
+    return pixels;
+}
+
+QVector<QRgb> decodeTightGradientFilter(const QByteArray& data, int width, int height)
+{
+    const int pixelCount = width * height;
+    QVector<QRgb> pixels;
+    if (pixelCount <= 0 || data.size() < pixelCount * 3) {
+        return pixels;
+    }
+
+    const auto* bytes = reinterpret_cast<const uchar*>(data.constData());
+    auto predict = [](int left, int up, int upLeft) {
+        return qBound(0, left + up - upLeft, 255);
+    };
+
+    QVector<int> rChan(pixelCount);
+    QVector<int> gChan(pixelCount);
+    QVector<int> bChan(pixelCount);
+    for (int y = 0; y < height; ++y) {
+        for (int x = 0; x < width; ++x) {
+            const int idx = (y * width) + x;
+            const uchar* px = bytes + (idx * 3);
+            // TPIXEL order matches rgbFromPixelBytes: B,G,R.
+            const int deltaB = px[0];
+            const int deltaG = px[1];
+            const int deltaR = px[2];
+
+            const int leftR = (x > 0) ? rChan[idx - 1] : 0;
+            const int leftG = (x > 0) ? gChan[idx - 1] : 0;
+            const int leftB = (x > 0) ? bChan[idx - 1] : 0;
+            const int upR = (y > 0) ? rChan[idx - width] : 0;
+            const int upG = (y > 0) ? gChan[idx - width] : 0;
+            const int upB = (y > 0) ? bChan[idx - width] : 0;
+            const int upLeftR = (x > 0 && y > 0) ? rChan[idx - width - 1] : 0;
+            const int upLeftG = (x > 0 && y > 0) ? gChan[idx - width - 1] : 0;
+            const int upLeftB = (x > 0 && y > 0) ? bChan[idx - width - 1] : 0;
+
+            rChan[idx] = (predict(leftR, upR, upLeftR) + deltaR) & 0xFF;
+            gChan[idx] = (predict(leftG, upG, upLeftG) + deltaG) & 0xFF;
+            bChan[idx] = (predict(leftB, upB, upLeftB) + deltaB) & 0xFF;
+        }
+    }
+
+    pixels.reserve(pixelCount);
+    for (int i = 0; i < pixelCount; ++i) {
+        pixels.append(qRgb(rChan.at(i), gChan.at(i), bChan.at(i)));
+    }
+    return pixels;
+}
+
+}

src/vnc_pixel_codecs.h

@@ -0,0 +1,109 @@
+#ifndef ORBITHUB_VNC_PIXEL_CODECS_H
+#define ORBITHUB_VNC_PIXEL_CODECS_H
+
+#include <QByteArray>
+#include <QRect>
+#include <QRgb>
+#include <QVector>
+
+// Pure, state-free decode helpers for VNC/RFB pixel encodings, kept out of
+// VncSessionBackend so the wire-sequencing (when to read what off the
+// socket) and wire-decoding (how to interpret already-buffered bytes) stay
+// separate and the latter is unit-testable without a live connection.
+namespace VncPixelCodecs {
+
+// Converts one pixel's worth of raw bytes as sent under
+// VncSessionBackend's negotiated SetPixelFormat (32bpp, little-endian,
+// byte order B,G,R,pad) into a QRgb.
+QRgb rgbFromPixelBytes(const uchar* bytes);
+
+// A single filled rectangle, in tile-local coordinates (0,0 = the tile's
+// own top-left corner, not the enclosing FramebufferUpdate rectangle's).
+struct HextileSubrect {
+    QRect rect;
+    QRgb color = 0;
+};
+
+// RFC 6143 SS7.7.4 Hextile tile subencoding byte flags.
+namespace HextileFlags {
+constexpr quint8 kRaw = 0x01;
+constexpr quint8 kBackgroundSpecified = 0x02;
+constexpr quint8 kForegroundSpecified = 0x04;
+constexpr quint8 kAnySubrects = 0x08;
+constexpr quint8 kSubrectsColoured = 0x10;
+}
+
+// Byte length of a Hextile tile's "fixed" metadata -- the optional
+// background/foreground color updates plus the optional subrect count --
+// derivable from the subencoding byte alone, before any of those bytes are
+// available. Only meaningful when HextileFlags::kRaw is *not* set (a Raw
+// tile has no metadata at all, just tileWidth*tileHeight raw pixels).
+int hextileFixedMetaByteCount(quint8 subencoding);
+
+// Parses the `hextileFixedMetaByteCount(subencoding)` bytes described
+// above. Updates *background/*foreground in place only when the
+// corresponding flag is set in `subencoding` -- callers should persist
+// their previous values across tiles in the same rectangle and pass them
+// in here unchanged when a color isn't re-specified, since RFC 6143 has
+// each tile inherit the last-specified colors. Returns the subrect count
+// (0 if HextileFlags::kAnySubrects isn't set).
+int decodeHextileFixedMeta(quint8 subencoding, const QByteArray& data, QRgb* background,
+                           QRgb* foreground);
+
+// Byte length of `subrectCount` subrects' worth of data, given whether
+// they're individually colored (HextileFlags::kSubrectsColoured).
+int hextileSubrectByteCount(bool coloured, int subrectCount);
+
+// Parses `subrectCount` subrects (xy + wh bytes, plus a per-subrect color
+// when `coloured`) out of `data`, substituting `foreground` in for any
+// that aren't individually colored.
+QVector<HextileSubrect> decodeHextileSubrects(bool coloured, int subrectCount,
+                                              const QByteArray& data, QRgb foreground);
+
+// Decodes one ZRLE tile (RFC 6143 SS7.7.6) from `data`, starting at
+// `offset` (which must point at the tile's own 1-byte subencoding).
+// `data` holds an entire rectangle's worth of already-zlib-decompressed
+// bytes (possibly several tiles' worth) -- this reads only as much as the
+// one tile needs and never looks past `data.size()`. On success, appends
+// exactly tileWidth*tileHeight pixels (row-major) to `pixels` (which is
+// NOT cleared first, so callers can accumulate across tiles if desired --
+// VncSessionBackend clears/reuses a fresh vector per tile) and returns the
+// number of bytes consumed. Returns -1 for a malformed/truncated tile
+// (should never happen against a spec-compliant server, but must not read
+// out of bounds against an adversarial or buggy one).
+int decodeZrleTile(const QByteArray& data, int offset, int tileWidth, int tileHeight,
+                   QVector<QRgb>& pixels);
+
+// Tight encoding (RFC 6143 SS7.7.4) filters. Unlike Hextile/ZRLE, a Tight
+// rectangle is never internally tiled -- these operate on the whole
+// rectangle's already-decompressed (or, for very small payloads the real
+// protocol allows to skip compression entirely, raw -- NOT handled by this
+// implementation, see VncSessionBackend's class comment) filtered byte
+// stream at once. Each returns exactly width*height pixels on success; a
+// short/malformed result (any size other than width*height, including an
+// empty vector) signals truncated/invalid input to the caller.
+
+// "Copy" filter: `data` is exactly width*height TPIXELs (3 bytes each,
+// row-major, same B,G,R order as rgbFromPixelBytes/ZRLE's CPIXEL).
+QVector<QRgb> decodeTightCopyFilter(const QByteArray& data, int width, int height);
+
+// "Palette" filter: `data` is a 1-byte (paletteSize-1) count, then
+// paletteSize TPIXELs, then a *continuous* (not row-padded, unlike ZRLE's
+// packed palette) MSB-first bit-packed index stream covering width*height
+// pixels, with bits-per-pixel derived from paletteSize the same way ZRLE's
+// packed palette does (<=2 colors: 1 bit; <=4: 2 bits; <=16: 4 bits;
+// otherwise 8 bits/1 byte per index, up to 256 colors).
+QVector<QRgb> decodeTightPaletteFilter(const QByteArray& data, int width, int height);
+
+// "Gradient" filter: `data` is exactly width*height TPIXELs, each channel
+// (R,G,B independently) carrying a delta from a predicted value computed
+// from already-decoded neighbors (predicted = clamp(left + up - upleft,
+// 0, 255); treated as 0 past the first row/column). This is the least
+// commonly exercised of the three Tight filters in real-world traffic and
+// the one this implementation has the lowest confidence in byte-for-byte
+// -- flagged for extra scrutiny/testing.
+QVector<QRgb> decodeTightGradientFilter(const QByteArray& data, int width, int height);
+
+}
+
+#endif

src/vnc_session_backend.h

@@ -0,0 +1,249 @@
+#ifndef ORBITHUB_VNC_SESSION_BACKEND_H
+#define ORBITHUB_VNC_SESSION_BACKEND_H
+
+#include "session_backend.h"
+
+#include <QAbstractSocket>
+#include <QByteArray>
+#include <QImage>
+#include <QRect>
+#include <QRgb>
+
+#include <array>
+
+class QTcpSocket;
+struct z_stream_s;
+
+// Implements RFB (RFC 6143) directly against QTcpSocket -- there is no
+// permissively licensed VNC client library to vendor the way FreeRDP was
+// for RDP (LibVNCClient is GPLv2, gtk-vnc is LGPL but GTK-tied), so this is
+// an original implementation. Threading follows SshSessionBackend's model
+// (a QObject moved to its own QThread, driven by Qt's own async socket
+// signals) rather than RdpSessionBackend's manual worker-thread/blocking
+// loop, since QTcpSocket is already async -- there's no legacy synchronous
+// C API to wrangle here.
+//
+// Scope (see plan / issue #3 for the full rationale): standard VNC
+// Authentication (security type 2), no-auth (type 1), and two Apple
+// Screen Sharing schemes, neither part of RFC 6143 and neither officially
+// documented by Apple: type 30 (Diffie-Hellman + AES -- see
+// vnc_apple_dh_auth.h) and type 33 (RSA + AES -- see
+// vnc_apple_rsa_auth.h). Modern macOS advertises both. Type 30's wire
+// format is confirmed against an independent, authoritative source
+// (neatvnc's rfb-proto.h, which documents the exact struct layout) and
+// verified live against a real macOS Screen Sharing server. Type 33's
+// implementation is sourced from the `asyncvnc` PyPI package (a real
+// client) but hasn't been gotten working live -- the server closes the
+// connection right after the client's initial request for its RSA host
+// key, suggesting either a transcription error or that this specific
+// macOS version's type 33 sub-protocol has evolved from what that
+// reference assumes; kept as a fallback pending further investigation.
+// Preference when multiple are offered: None > AppleDH(30) >
+// AppleRSA(33) > VNCAuth(2). Raw + CopyRect + Hextile + ZRLE + Tight
+// encodings. No dynamic resize. Clipboard sync
+// (Latin-1 only, per RFB's ServerCutText/ClientCutText) and remote cursor
+// shape sync (the Cursor pseudo-encoding) are supported.
+//
+// Tight decoding gap: the real protocol allows the server to skip zlib
+// compression entirely for very small Basic-mode payloads; this decoder
+// always attempts to zlib-inflate them, so a server that takes that
+// shortcut on a given rectangle would have that one rectangle fail rather
+// than decode. This is intentionally not special-cased (the exact trigger
+// condition/wire signaling for it could not be verified with confidence
+// against the RFC text alone, and it only affects rare, tiny rectangles --
+// solid or near-solid tiny areas are virtually always sent as Fill instead
+// in practice) -- see docs/PROGRESS.md.
+class VncSessionBackend : public SessionBackend
+{
+    Q_OBJECT
+
+public:
+    explicit VncSessionBackend(const Profile& profile, QObject* parent = nullptr);
+    ~VncSessionBackend() override;
+
+    // Pure, state-free helpers exposed as public statics purely so tests
+    // can exercise them without a live connection.
+    static QByteArray vncAuthResponse(const QByteArray& challenge, const QString& password);
+    static QByteArray desKeyFromPassword(const QString& password);
+    static QString mapSocketError(QAbstractSocket::SocketError error, const QString& rawDetail);
+    static quint32 keysymForQtKey(int key, const QString& text);
+
+public slots:
+    void connectSession(const SessionConnectOptions& options) override;
+    void disconnectSession() override;
+    void reconnectSession(const SessionConnectOptions& options) override;
+    void sendInput(const QString& input) override;
+    void confirmHostKey(bool trustHost) override;
+    void updateTerminalSize(int columns, int rows) override;
+    void sendKeyEvent(int key,
+                      quint32 nativeScanCode,
+                      const QString& text,
+                      bool pressed,
+                      int modifiers) override;
+    void sendMouseMoveEvent(int x, int y) override;
+    void sendMouseButtonEvent(int x, int y, int button, bool pressed) override;
+    void sendMouseWheelEvent(int x, int y, int deltaX, int deltaY) override;
+    void setClipboardText(const QString& text) override;
+    void provideUsername(const QString& username) override;
+
+private slots:
+    void onSocketConnected();
+    void onSocketReadyRead();
+    void onSocketDisconnected();
+    void onSocketErrorOccurred(QAbstractSocket::SocketError error);
+
+private:
+    enum class RfbState {
+        Idle,
+        WaitingProtocolVersion,
+        WaitingSecurityTypeCount,
+        WaitingSecurityTypeList,
+        WaitingSecurityTypeV33,
+        WaitingSecurityFailureReasonLength,
+        WaitingSecurityFailureReason,
+        WaitingVncAuthChallenge,
+        WaitingSecurityResult,
+        WaitingSecurityResultReasonLength,
+        WaitingSecurityResultReason,
+        WaitingServerInitHeader,
+        WaitingServerName,
+        WaitingServerMessageType,
+        WaitingFramebufferUpdateHeader,
+        WaitingRectangleHeader,
+        WaitingRawPixelData,
+        WaitingCopyRectSource,
+        WaitingCursorPixelData,
+        WaitingHextileTileSubencoding,
+        WaitingHextileTileMeta,
+        WaitingHextileSubrectData,
+        WaitingHextileRawTileData,
+        WaitingZrleCompressedLength,
+        WaitingZrleCompressedData,
+        WaitingTightCompressionControl,
+        WaitingTightFillColor,
+        WaitingTightFilterId,
+        WaitingTightLengthByte,
+        WaitingTightPayload,
+        WaitingAppleAuthParams,
+        WaitingAppleAuthPrimeAndServerKey,
+        WaitingAppleRsaHostKeyHeader,
+        WaitingAppleRsaHostKeyBytes,
+        WaitingSetColourMapHeader,
+        WaitingSetColourMapData,
+        WaitingServerCutTextHeader,
+        WaitingServerCutTextData,
+    };
+
+    struct PendingRectangle {
+        int x = 0;
+        int y = 0;
+        int width = 0;
+        int height = 0;
+        qint32 encoding = 0;
+    };
+
+    QTcpSocket* m_socket;
+    SessionState m_state;
+    RfbState m_rfbState;
+    QByteArray m_recvBuffer;
+    bool m_userInitiatedDisconnect;
+    bool m_reconnectPending;
+    SessionConnectOptions m_reconnectOptions;
+    SessionConnectOptions m_activeOptions;
+
+    int m_negotiatedMinorVersion;
+    int m_securityTypeCount;
+    QByteArray m_offeredSecurityTypes;
+    quint8 m_chosenSecurityType;
+    quint32 m_pendingLength;
+
+    QImage m_framebuffer;
+    int m_pendingRectanglesRemaining;
+    PendingRectangle m_currentRectangle;
+
+    quint8 m_pointerButtonMask;
+    int m_lastPointerX;
+    int m_lastPointerY;
+
+    // Hextile decode state (RFC 6143 SS7.7.4): tile-cursor position relative
+    // to the current rectangle's origin, plus the background/foreground
+    // colors, which persist across tiles within one rectangle whenever a
+    // tile doesn't re-specify them.
+    int m_hextileTileX;
+    int m_hextileTileY;
+    QRgb m_hextileBackground;
+    QRgb m_hextileForeground;
+    quint8 m_hextileSubencoding;
+    int m_hextileSubrectsRemaining;
+    bool m_hextileSubrectsColoured;
+
+    // ZRLE's zlib stream (RFC 6143 SS7.7.6) persists for the whole
+    // connection, not per-rectangle or per-update -- lazily initialized on
+    // the first ZRLE rectangle, torn down and reset on every fresh
+    // connect/reconnect via resetProtocolState(). z_stream_s is only
+    // forward-declared here so <zlib.h> doesn't leak into every includer of
+    // this header; the full type is only needed in the .cpp.
+    z_stream_s* m_zrleInflateStream;
+    bool m_zrleInflateInitialized;
+
+    // Tight decode state (RFC 6143 SS7.7.4). Unlike ZRLE, Tight's "Basic"
+    // compression mode has 4 independent persistent zlib streams (chosen
+    // per-rectangle by 2 bits of the compression-control byte), each with
+    // its own lifecycle -- reset individually via the control byte's low 4
+    // bits, otherwise persisting like ZRLE's single stream.
+    std::array<z_stream_s*, 4> m_tightInflateStreams;
+    std::array<bool, 4> m_tightInflateInitialized;
+    quint8 m_tightCompressionMode; // compression-control byte >> 4
+    quint8 m_tightFilterId;
+    int m_tightLengthByteIndex;
+
+    // Apple Screen Sharing authentication state (security type 30, not
+    // part of RFC 6143 -- see vnc_apple_dh_auth.h). Wire format confirmed
+    // empirically against a real macOS Screen Sharing server: a literal
+    // 2-byte generator (not length-prefixed -- there is no separate
+    // generator-length field), then a 2-byte key length that applies to
+    // *both* the prime and the server's public key that follow. Both
+    // members must persist from WaitingAppleAuthParams until the combined
+    // prime+server-public-key buffer (2x the key length) has fully
+    // arrived, since m_pendingLength gets reused to track that combined
+    // byte count in the meantime.
+    QByteArray m_appleAuthGenerator;
+    quint32 m_appleAuthKeyLength;
+
+    // Apple auth (types 30 and 33) is the only case where VNC ever needs a
+    // username -- plain VNC Authentication and no-auth never do, so this
+    // isn't asked for upfront. If profile().username is empty when an
+    // Apple-auth response is about to be computed, processReceiveBuffer()
+    // pauses (leaving the already-buffered bytes untouched so re-entry
+    // re-parses them identically) and emits usernameRequested(); resumed
+    // by provideUsername() once SessionTab answers.
+    bool m_waitingForUsername;
+    QString m_promptedUsername;
+
+    void setState(SessionState state, const QString& message);
+    void resetProtocolState();
+    void processReceiveBuffer();
+    bool haveBytes(int count) const;
+    void sendVersionReply();
+    void sendClientInit();
+    void sendSetPixelFormatAndEncodings();
+    void requestFramebufferUpdate(bool incremental);
+    void failConnection(const QString& displayMessage, const QString& rawMessage);
+    void finishHandshakeIntoRunningState();
+    void onRectangleFinished();
+    void sendPointerEvent();
+    void sendWheelClick(quint8 wheelBit);
+    void sendClientCutText(const QString& text);
+    void sendAppleRsaHostKeyRequest();
+    QRect currentHextileTileRect() const;
+    void advanceHextileTile();
+    bool inflateTightStream(int streamIndex, const QByteArray& compressed, QByteArray* decompressed);
+    QString effectiveUsername() const;
+    // Returns false (and pauses, emitting usernameRequested() at most once
+    // until provideUsername() resumes processing) if a username is needed
+    // but not yet available. Callers must return from processReceiveBuffer()
+    // immediately when this returns false, without consuming any bytes.
+    bool ensureUsernameAvailable();
+};
+
+#endif

tests/CMakeLists.txt

@@ -0,0 +1,64 @@
+add_executable(test_profile_repository
+    test_profile_repository.cpp
+    ${CMAKE_SOURCE_DIR}/src/profile_repository.cpp
+)
+target_include_directories(test_profile_repository PRIVATE ${CMAKE_SOURCE_DIR}/src)
+target_link_libraries(test_profile_repository PRIVATE Qt6::Core Qt6::Sql Qt6::Test)
+add_test(NAME test_profile_repository COMMAND test_profile_repository)
+
+add_executable(test_mremoteng_importer
+    test_mremoteng_importer.cpp
+    ${CMAKE_SOURCE_DIR}/src/mremoteng_importer.cpp
+)
+target_include_directories(test_mremoteng_importer PRIVATE ${CMAKE_SOURCE_DIR}/src)
+target_link_libraries(test_mremoteng_importer PRIVATE Qt6::Core Qt6::Test)
+add_test(NAME test_mremoteng_importer COMMAND test_mremoteng_importer)
+
+add_executable(test_ssh_session_backend
+    test_ssh_session_backend.cpp
+    ${CMAKE_SOURCE_DIR}/src/ssh_session_backend.cpp
+    ${CMAKE_SOURCE_DIR}/src/session_backend.h
+)
+target_include_directories(test_ssh_session_backend PRIVATE ${CMAKE_SOURCE_DIR}/src)
+target_link_libraries(test_ssh_session_backend PRIVATE Qt6::Core Qt6::Gui Qt6::Test)
+target_compile_definitions(test_ssh_session_backend PRIVATE
+    ORBITHUB_TEST_FIXTURES_DIR="${CMAKE_CURRENT_SOURCE_DIR}/fixtures"
+)
+add_test(NAME test_ssh_session_backend COMMAND test_ssh_session_backend)
+
+add_executable(test_vnc_session_backend
+    test_vnc_session_backend.cpp
+    ${CMAKE_SOURCE_DIR}/src/vnc_session_backend.cpp
+    ${CMAKE_SOURCE_DIR}/src/vnc_pixel_codecs.cpp
+    ${CMAKE_SOURCE_DIR}/src/vnc_apple_dh_auth.cpp
+    ${CMAKE_SOURCE_DIR}/src/vnc_apple_rsa_auth.cpp
+    ${CMAKE_SOURCE_DIR}/src/session_backend.h
+)
+target_include_directories(test_vnc_session_backend PRIVATE ${CMAKE_SOURCE_DIR}/src)
+target_link_libraries(test_vnc_session_backend PRIVATE
+    Qt6::Core Qt6::Gui Qt6::Network Qt6::Test OpenSSL::Crypto ZLIB::ZLIB JPEG::JPEG
+)
+add_test(NAME test_vnc_session_backend COMMAND test_vnc_session_backend)
+
+if(TARGET freerdp AND TARGET winpr)
+    add_executable(test_rdp_session_backend
+        test_rdp_session_backend.cpp
+        ${CMAKE_SOURCE_DIR}/src/rdp_session_backend.cpp
+        ${CMAKE_SOURCE_DIR}/src/session_backend.h
+    )
+    target_include_directories(test_rdp_session_backend PRIVATE
+        ${CMAKE_SOURCE_DIR}/src
+        ${CMAKE_SOURCE_DIR}/third_party/FreeRDP/include
+        ${CMAKE_SOURCE_DIR}/third_party/FreeRDP/winpr/include
+        ${CMAKE_BINARY_DIR}/third_party/FreeRDP/include
+        ${CMAKE_BINARY_DIR}/third_party/FreeRDP/winpr/include
+    )
+    target_compile_definitions(test_rdp_session_backend PRIVATE ORBITHUB_HAS_FREERDP)
+    target_link_libraries(test_rdp_session_backend PRIVATE Qt6::Core Qt6::Gui Qt6::Test freerdp winpr)
+    if(TARGET freerdp-client)
+        target_link_libraries(test_rdp_session_backend PRIVATE freerdp-client)
+    endif()
+    add_test(NAME test_rdp_session_backend COMMAND test_rdp_session_backend)
+else()
+    message(STATUS "FreeRDP targets not available -- skipping test_rdp_session_backend")
+endif()

tests/fixtures/fake_ssh.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+# Minimal, deterministic stand-in for the real `ssh` binary, used by
+# SshSessionBackend's state-machine tests so they never touch a real
+# network or SSH server. Behavior is selected by which fixture hostname
+# appears among argv (SshSessionBackend always passes the profile's
+# host, optionally as user@host, as the final argument).
+for arg in "$@"; do
+    case "$arg" in
+        *@succeed|succeed)
+            echo "Welcome to the fake host."
+            # Stay alive echoing stdin back (simulates an interactive
+            # session) until the backend terminates us.
+            while IFS= read -r line; do
+                echo "$line"
+            done
+            exit 0
+            ;;
+        *@fail-auth|fail-auth)
+            echo "Permission denied (publickey,password)." >&2
+            exit 255
+            ;;
+        *@refuse|refuse)
+            echo "ssh: connect to host refuse port 22: Connection refused" >&2
+            exit 255
+            ;;
+    esac
+done
+echo "fake_ssh.sh: no recognized fixture host in arguments: $*" >&2
+exit 1

tests/test_mremoteng_importer.cpp

@@ -0,0 +1,124 @@
+#include "mremoteng_importer.h"
+
+#include "test_mremoteng_importer_fixtures.h"
+
+#include <QTest>
+
+#include <algorithm>
+
+class TestMRemoteNGImporter : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void parsesFoldersAndProfilesFromRealisticSample();
+    void mapsRdpConnectionFieldsCorrectly();
+    void mapsSshConnectionFieldsCorrectly();
+    void skipsUnsupportedProtocolWithoutDroppingSilently();
+    void neverImportsPasswordField();
+    void refusesFullFileEncryptedExports();
+    void refusesUnrecognizedRootElement();
+    void refusesMalformedXml();
+    void refusesEmptyInput();
+};
+
+void TestMRemoteNGImporter::parsesFoldersAndProfilesFromRealisticSample()
+{
+    const MRemoteNGImportResult result = parseMRemoteNGConnections(QByteArray(mRemoteNGSampleXml()));
+    QVERIFY(result.errorMessage.isEmpty());
+
+    QCOMPARE(result.folders.size(), size_t(2));
+    QCOMPARE(result.folders[0], QStringLiteral("Work"));
+    QCOMPARE(result.folders[1], QStringLiteral("Work/Servers"));
+
+    // 3 connection nodes in the sample: DC (RDP), build-box (SSH2),
+    // oldkiosk (VNC, unsupported) -- only the first two should come
+    // through as imported profiles.
+    QCOMPARE(result.profiles.size(), size_t(2));
+    QCOMPARE(result.skippedUnsupportedProtocol.size(), 1);
+}
+
+void TestMRemoteNGImporter::mapsRdpConnectionFieldsCorrectly()
+{
+    const MRemoteNGImportResult result = parseMRemoteNGConnections(QByteArray(mRemoteNGSampleXml()));
+    const auto it = std::find_if(result.profiles.begin(), result.profiles.end(),
+                                 [](const MRemoteNGImportedProfile& p) {
+                                     return p.profile.name == QStringLiteral("DC");
+                                 });
+    QVERIFY(it != result.profiles.end());
+    QCOMPARE(it->profile.host, QStringLiteral("10.0.0.5"));
+    QCOMPARE(it->profile.port, 3389);
+    QCOMPARE(it->profile.username, QStringLiteral("Administrator"));
+    QCOMPARE(it->profile.protocol, QStringLiteral("RDP"));
+    QCOMPARE(it->profile.domain, QStringLiteral("CORP"));
+    QCOMPARE(it->folderPath, QStringLiteral("Work"));
+}
+
+void TestMRemoteNGImporter::mapsSshConnectionFieldsCorrectly()
+{
+    const MRemoteNGImportResult result = parseMRemoteNGConnections(QByteArray(mRemoteNGSampleXml()));
+    const auto it = std::find_if(result.profiles.begin(), result.profiles.end(),
+                                 [](const MRemoteNGImportedProfile& p) {
+                                     return p.profile.name == QStringLiteral("build-box");
+                                 });
+    QVERIFY(it != result.profiles.end());
+    QCOMPARE(it->profile.host, QStringLiteral("build.internal"));
+    QCOMPARE(it->profile.port, 22);
+    QCOMPARE(it->profile.username, QStringLiteral("deploy"));
+    // SSH1/SSH2 both collapse to OrbitHub's single "SSH" protocol.
+    QCOMPARE(it->profile.protocol, QStringLiteral("SSH"));
+    QCOMPARE(it->profile.authMode, QStringLiteral("Password"));
+    // Domain is RDP-only; must not leak through for SSH.
+    QCOMPARE(it->profile.domain, QString());
+    QCOMPARE(it->folderPath, QStringLiteral("Work/Servers"));
+}
+
+void TestMRemoteNGImporter::skipsUnsupportedProtocolWithoutDroppingSilently()
+{
+    const MRemoteNGImportResult result = parseMRemoteNGConnections(QByteArray(mRemoteNGSampleXml()));
+    QCOMPARE(result.skippedUnsupportedProtocol.size(), 1);
+    QVERIFY(result.skippedUnsupportedProtocol[0].contains(QStringLiteral("oldkiosk")));
+    QVERIFY(result.skippedUnsupportedProtocol[0].contains(QStringLiteral("VNC")));
+}
+
+void TestMRemoteNGImporter::neverImportsPasswordField()
+{
+    // Profile has no password-storing field at all -- this test exists to
+    // document that guarantee, not to probe internals that don't exist.
+    const MRemoteNGImportResult result = parseMRemoteNGConnections(QByteArray(mRemoteNGSampleXml()));
+    QVERIFY(!result.profiles.empty());
+    for (const MRemoteNGImportedProfile& item : result.profiles) {
+        QCOMPARE(item.profile.authMode, QStringLiteral("Password"));
+        QVERIFY(item.profile.privateKeyPath.isEmpty());
+    }
+}
+
+void TestMRemoteNGImporter::refusesFullFileEncryptedExports()
+{
+    const MRemoteNGImportResult result = parseMRemoteNGConnections(QByteArray(mRemoteNGFullFileEncryptedXml()));
+    QVERIFY(!result.errorMessage.isEmpty());
+    QVERIFY(result.errorMessage.contains(QStringLiteral("full file encryption"), Qt::CaseInsensitive));
+    QVERIFY(result.profiles.empty());
+}
+
+void TestMRemoteNGImporter::refusesUnrecognizedRootElement()
+{
+    const MRemoteNGImportResult result = parseMRemoteNGConnections(QByteArray(mRemoteNGWrongRootXml()));
+    QVERIFY(!result.errorMessage.isEmpty());
+}
+
+void TestMRemoteNGImporter::refusesMalformedXml()
+{
+    const MRemoteNGImportResult result =
+        parseMRemoteNGConnections(QByteArray("<mrng:Connections><Node "));
+    QVERIFY(!result.errorMessage.isEmpty());
+}
+
+void TestMRemoteNGImporter::refusesEmptyInput()
+{
+    const MRemoteNGImportResult result = parseMRemoteNGConnections(QByteArray());
+    QVERIFY(!result.errorMessage.isEmpty());
+}
+
+QTEST_APPLESS_MAIN(TestMRemoteNGImporter)
+#include "test_mremoteng_importer.moc"

tests/test_mremoteng_importer_fixtures.h

@@ -0,0 +1,47 @@
+#ifndef ORBITHUB_TEST_MREMOTENG_IMPORTER_FIXTURES_H
+#define ORBITHUB_TEST_MREMOTENG_IMPORTER_FIXTURES_H
+
+// Kept out of the moc-processed test .cpp: a literal "//" inside a raw
+// string literal (as in the xmlns URL below) confuses moc's lexer into
+// thinking a line comment started there, which silently desyncs the rest
+// of its parse and drops the QObject-derived test class entirely (no
+// error, just "No relevant classes found" and a missing vtable at link
+// time). Plain, non-QObject headers are never moc-scanned, so this is
+// immune to that.
+
+// Modeled on a real mRemoteNG confCons.xml export (attribute names and
+// root-element shape verified against mRemoteNG's own
+// XmlConnectionsDeserializer.cs and a real exported sample), covering:
+// nested folders, an RDP connection, an SSH2 connection (protocol must
+// map to "SSH"), and a VNC connection (unsupported -- must be skipped,
+// not dropped silently).
+inline const char* mRemoteNGSampleXml()
+{
+    return R"(<?xml version="1.0" encoding="utf-8"?>
+<mrng:Connections xmlns:mrng="http:)" R"(//mremoteng.org" Name="Connections" Export="false" EncryptionEngine="AES" BlockCipherMode="GCM" KdfIterations="1000" FullFileEncryption="false" Protected="" ConfVersion="2.6">
+    <Node Name="Work" Type="Container" Descr="" Expanded="true">
+        <Node Name="DC" Type="Connection" Descr="" Username="Administrator" Domain="CORP" Password="aEWNFV5uGcjUHF0uS17QTdT9kVqtKCPeoC0Nw5dmaPFjNQ2kt/zO5xDqE4HdVmHAowVRdC7emf7lWWA10dQKiw==" Hostname="10.0.0.5" Protocol="RDP" Port="3389" />
+        <Node Name="Servers" Type="Container" Descr="" Expanded="true">
+            <Node Name="build-box" Type="Connection" Descr="" Username="deploy" Domain="" Password="yhgmiu5bbuamU3qMUKc/uYDdmbMrJZ" Hostname="build.internal" Protocol="SSH2" Port="22" />
+        </Node>
+    </Node>
+    <Node Name="oldkiosk" Type="Connection" Descr="" Username="" Domain="" Password="" Hostname="kiosk.internal" Protocol="VNC" Port="5900" />
+</mrng:Connections>
+)";
+}
+
+inline const char* mRemoteNGFullFileEncryptedXml()
+{
+    return R"(<?xml version="1.0" encoding="utf-8"?>
+<mrng:Connections xmlns:mrng="http:)" R"(//mremoteng.org" Name="Connections" Export="false" EncryptionEngine="AES" BlockCipherMode="GCM" KdfIterations="1000" FullFileEncryption="true" Protected="somehash" ConfVersion="2.6">SomeOpaqueBase64Blob==</mrng:Connections>
+)";
+}
+
+inline const char* mRemoteNGWrongRootXml()
+{
+    return R"(<?xml version="1.0" encoding="utf-8"?>
+<SomeOtherFormat/>
+)";
+}
+
+#endif

tests/test_profile_repository.cpp

@@ -0,0 +1,375 @@
+#include "profile_repository.h"
+
+#include <QTemporaryDir>
+#include <QTest>
+
+#include <memory>
+
+namespace {
+Profile makeSshProfile(const QString& name = QStringLiteral("Prod SSH Box"))
+{
+    Profile profile;
+    profile.name = name;
+    profile.host = QStringLiteral("prod.example.com");
+    profile.port = 22;
+    profile.username = QStringLiteral("deploy");
+    profile.protocol = QStringLiteral("SSH");
+    profile.authMode = QStringLiteral("Password");
+    profile.tags = QStringLiteral("prod,linux");
+    return profile;
+}
+
+Profile makeRdpProfile(const QString& name = QStringLiteral("Windows RDP Box"))
+{
+    Profile profile;
+    profile.name = name;
+    profile.host = QStringLiteral("win.example.com");
+    profile.port = 3389;
+    profile.username = QStringLiteral("admin");
+    profile.domain = QStringLiteral("CORP");
+    profile.protocol = QStringLiteral("RDP");
+    profile.rdpSecurityMode = QStringLiteral("NLA");
+    profile.rdpPerformanceProfile = QStringLiteral("Best Performance");
+    return profile;
+}
+}
+
+class TestProfileRepository : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void init();
+    void cleanup();
+
+    void initializesCleanly();
+    void createAndGetSshProfile();
+    void createAndGetRdpProfile();
+    void createProfileRejectsMissingName();
+    void createProfileRejectsMissingHost();
+    void createProfileRejectsInvalidPort();
+    void createProfileRejectsMissingUsernameForSsh();
+    void createProfileRejectsMissingPrivateKeyForKeyAuth();
+    void createProfileRejectsDuplicateName();
+    void updateProfilePersistsChanges();
+    void deleteProfileRemovesIt();
+    void getProfileReturnsNulloptForUnknownId();
+    void listProfilesFiltersBySearchQuery();
+    void listProfilesSortsByRequestedOrder();
+    void tagsAreTrimmedDedupedAndJoined();
+    void emptyTagsRoundTripAsEmpty();
+    void folderCreateAndListRoundTrips();
+    void folderCreateIgnoresDuplicates();
+    void folderPathIsNormalized();
+    void deleteEmptyFolderRemovesIt();
+    void deleteFolderMovesDirectProfilesToParent();
+    void deleteRootLevelFolderMovesProfilesToRoot();
+    void deleteFolderShiftsSubfoldersAndTheirProfilesUp();
+    void deleteFolderRejectsEmptyPath();
+    void deleteNonexistentFolderSucceedsAsNoOp();
+
+private:
+    std::unique_ptr<QTemporaryDir> m_tempDir;
+    std::unique_ptr<ProfileRepository> m_repo;
+};
+
+void TestProfileRepository::init()
+{
+    m_tempDir = std::make_unique<QTemporaryDir>();
+    QVERIFY(m_tempDir->isValid());
+    m_repo = std::make_unique<ProfileRepository>(m_tempDir->filePath(QStringLiteral("test.sqlite")));
+}
+
+void TestProfileRepository::cleanup()
+{
+    m_repo.reset();
+    m_tempDir.reset();
+}
+
+void TestProfileRepository::initializesCleanly()
+{
+    QCOMPARE(m_repo->initError(), QString());
+    QCOMPARE(m_repo->listProfiles().size(), size_t(0));
+    QCOMPARE(m_repo->listFolders().size(), size_t(0));
+}
+
+void TestProfileRepository::createAndGetSshProfile()
+{
+    const Profile input = makeSshProfile();
+    const std::optional<Profile> created = m_repo->createProfile(input);
+    QVERIFY(created.has_value());
+    QVERIFY(created->id > 0);
+
+    const std::optional<Profile> fetched = m_repo->getProfile(created->id);
+    QVERIFY(fetched.has_value());
+    QCOMPARE(fetched->name, input.name);
+    QCOMPARE(fetched->host, input.host);
+    QCOMPARE(fetched->port, input.port);
+    QCOMPARE(fetched->username, input.username);
+    QCOMPARE(fetched->protocol, QStringLiteral("SSH"));
+    QCOMPARE(fetched->authMode, QStringLiteral("Password"));
+    QCOMPARE(fetched->tags, QStringLiteral("prod, linux"));
+}
+
+void TestProfileRepository::createAndGetRdpProfile()
+{
+    const Profile input = makeRdpProfile();
+    const std::optional<Profile> created = m_repo->createProfile(input);
+    QVERIFY(created.has_value());
+
+    const std::optional<Profile> fetched = m_repo->getProfile(created->id);
+    QVERIFY(fetched.has_value());
+    QCOMPARE(fetched->protocol, QStringLiteral("RDP"));
+    QCOMPARE(fetched->domain, QStringLiteral("CORP"));
+    QCOMPARE(fetched->rdpSecurityMode, QStringLiteral("NLA"));
+    QCOMPARE(fetched->rdpPerformanceProfile, QStringLiteral("Best Performance"));
+    QCOMPARE(fetched->port, 3389);
+    // Auth-mode/private-key fields are SSH-only and must not leak through
+    // for a non-SSH protocol.
+    QCOMPARE(fetched->authMode, QStringLiteral("Password"));
+    QCOMPARE(fetched->privateKeyPath, QString());
+}
+
+void TestProfileRepository::createProfileRejectsMissingName()
+{
+    Profile profile = makeSshProfile();
+    profile.name.clear();
+    QVERIFY(!m_repo->createProfile(profile).has_value());
+    QVERIFY(!m_repo->lastError().isEmpty());
+}
+
+void TestProfileRepository::createProfileRejectsMissingHost()
+{
+    Profile profile = makeSshProfile();
+    profile.host.clear();
+    QVERIFY(!m_repo->createProfile(profile).has_value());
+    QVERIFY(!m_repo->lastError().isEmpty());
+}
+
+void TestProfileRepository::createProfileRejectsInvalidPort()
+{
+    Profile profile = makeSshProfile();
+    profile.port = 0;
+    QVERIFY(!m_repo->createProfile(profile).has_value());
+
+    profile.port = 70000;
+    QVERIFY(!m_repo->createProfile(profile).has_value());
+}
+
+void TestProfileRepository::createProfileRejectsMissingUsernameForSsh()
+{
+    Profile profile = makeSshProfile();
+    profile.username.clear();
+    QVERIFY(!m_repo->createProfile(profile).has_value());
+}
+
+void TestProfileRepository::createProfileRejectsMissingPrivateKeyForKeyAuth()
+{
+    Profile profile = makeSshProfile();
+    profile.authMode = QStringLiteral("Private Key");
+    profile.privateKeyPath.clear();
+    QVERIFY(!m_repo->createProfile(profile).has_value());
+}
+
+void TestProfileRepository::createProfileRejectsDuplicateName()
+{
+    QVERIFY(m_repo->createProfile(makeSshProfile(QStringLiteral("Same Name"))).has_value());
+    QVERIFY(!m_repo->createProfile(makeSshProfile(QStringLiteral("Same Name"))).has_value());
+}
+
+void TestProfileRepository::updateProfilePersistsChanges()
+{
+    const std::optional<Profile> created = m_repo->createProfile(makeSshProfile());
+    QVERIFY(created.has_value());
+
+    Profile updated = created.value();
+    updated.host = QStringLiteral("new-host.example.com");
+    updated.port = 2222;
+    updated.tags = QStringLiteral("updated");
+    QVERIFY(m_repo->updateProfile(updated));
+
+    const std::optional<Profile> fetched = m_repo->getProfile(created->id);
+    QVERIFY(fetched.has_value());
+    QCOMPARE(fetched->host, QStringLiteral("new-host.example.com"));
+    QCOMPARE(fetched->port, 2222);
+    QCOMPARE(fetched->tags, QStringLiteral("updated"));
+}
+
+void TestProfileRepository::deleteProfileRemovesIt()
+{
+    const std::optional<Profile> created = m_repo->createProfile(makeSshProfile());
+    QVERIFY(created.has_value());
+    QVERIFY(m_repo->deleteProfile(created->id));
+    QVERIFY(!m_repo->getProfile(created->id).has_value());
+}
+
+void TestProfileRepository::getProfileReturnsNulloptForUnknownId()
+{
+    QVERIFY(!m_repo->getProfile(999999).has_value());
+}
+
+void TestProfileRepository::listProfilesFiltersBySearchQuery()
+{
+    QVERIFY(m_repo->createProfile(makeSshProfile(QStringLiteral("Alpha"))).has_value());
+    QVERIFY(m_repo->createProfile(makeRdpProfile(QStringLiteral("Beta"))).has_value());
+
+    const auto byName = m_repo->listProfiles(QStringLiteral("Alpha"));
+    QCOMPARE(byName.size(), size_t(1));
+    QCOMPARE(byName[0].name, QStringLiteral("Alpha"));
+
+    const auto byHost = m_repo->listProfiles(QStringLiteral("win.example"));
+    QCOMPARE(byHost.size(), size_t(1));
+    QCOMPARE(byHost[0].name, QStringLiteral("Beta"));
+
+    const auto byTag = m_repo->listProfiles(QStringLiteral("linux"));
+    QCOMPARE(byTag.size(), size_t(1));
+    QCOMPARE(byTag[0].name, QStringLiteral("Alpha"));
+
+    QCOMPARE(m_repo->listProfiles(QStringLiteral("nonexistent")).size(), size_t(0));
+}
+
+void TestProfileRepository::listProfilesSortsByRequestedOrder()
+{
+    QVERIFY(m_repo->createProfile(makeSshProfile(QStringLiteral("Zeta"))).has_value());
+    QVERIFY(m_repo->createProfile(makeRdpProfile(QStringLiteral("Alpha"))).has_value());
+
+    const auto byName = m_repo->listProfiles(QString(), ProfileSortOrder::NameAsc);
+    QCOMPARE(byName.size(), size_t(2));
+    QCOMPARE(byName[0].name, QStringLiteral("Alpha"));
+    QCOMPARE(byName[1].name, QStringLiteral("Zeta"));
+
+    const auto byProtocol = m_repo->listProfiles(QString(), ProfileSortOrder::ProtocolAsc);
+    QCOMPARE(byProtocol[0].protocol, QStringLiteral("RDP"));
+    QCOMPARE(byProtocol[1].protocol, QStringLiteral("SSH"));
+}
+
+void TestProfileRepository::tagsAreTrimmedDedupedAndJoined()
+{
+    Profile profile = makeSshProfile();
+    profile.tags = QStringLiteral(" prod ,, Prod , linux ,linux");
+    const std::optional<Profile> created = m_repo->createProfile(profile);
+    QVERIFY(created.has_value());
+
+    // createProfile()'s return value echoes the input as-is; normalization
+    // only happens on the DB round trip, so re-fetch to observe it.
+    const std::optional<Profile> fetched = m_repo->getProfile(created->id);
+    QVERIFY(fetched.has_value());
+    // Case-insensitive de-dup keeps the first-seen casing of each tag.
+    QCOMPARE(fetched->tags, QStringLiteral("prod, linux"));
+}
+
+void TestProfileRepository::emptyTagsRoundTripAsEmpty()
+{
+    const std::optional<Profile> created = m_repo->createProfile(makeRdpProfile());
+    QVERIFY(created.has_value());
+    const std::optional<Profile> fetched = m_repo->getProfile(created->id);
+    QVERIFY(fetched.has_value());
+    QCOMPARE(fetched->tags, QString());
+}
+
+void TestProfileRepository::folderCreateAndListRoundTrips()
+{
+    QVERIFY(m_repo->createFolder(QStringLiteral("Work/Servers")));
+    const auto folders = m_repo->listFolders();
+    QCOMPARE(folders.size(), size_t(1));
+    QCOMPARE(folders[0], QStringLiteral("Work/Servers"));
+}
+
+void TestProfileRepository::folderCreateIgnoresDuplicates()
+{
+    QVERIFY(m_repo->createFolder(QStringLiteral("Work")));
+    QVERIFY(m_repo->createFolder(QStringLiteral("Work")));
+    QCOMPARE(m_repo->listFolders().size(), size_t(1));
+}
+
+void TestProfileRepository::folderPathIsNormalized()
+{
+    QVERIFY(m_repo->createFolder(QStringLiteral("\\Work\\\\Servers\\")));
+    const auto folders = m_repo->listFolders();
+    QCOMPARE(folders.size(), size_t(1));
+    QCOMPARE(folders[0], QStringLiteral("Work/Servers"));
+}
+
+void TestProfileRepository::deleteEmptyFolderRemovesIt()
+{
+    QVERIFY(m_repo->createFolder(QStringLiteral("Empty")));
+    QVERIFY(m_repo->deleteFolder(QStringLiteral("Empty")));
+    QCOMPARE(m_repo->listFolders().size(), size_t(0));
+}
+
+void TestProfileRepository::deleteFolderMovesDirectProfilesToParent()
+{
+    QVERIFY(m_repo->createFolder(QStringLiteral("Work")));
+    Profile profile = makeSshProfile();
+    profile.folderPath = QStringLiteral("Work");
+    const std::optional<Profile> created = m_repo->createProfile(profile);
+    QVERIFY(created.has_value());
+
+    QVERIFY(m_repo->deleteFolder(QStringLiteral("Work")));
+    QCOMPARE(m_repo->listFolders().size(), size_t(0));
+
+    const std::optional<Profile> fetched = m_repo->getProfile(created->id);
+    QVERIFY(fetched.has_value());
+    // Deleting a folder is never destructive to profiles -- they shift up
+    // to take its place, here landing at the root since "Work" had no
+    // parent of its own.
+    QCOMPARE(fetched->folderPath, QString());
+}
+
+void TestProfileRepository::deleteRootLevelFolderMovesProfilesToRoot()
+{
+    Profile profile = makeRdpProfile();
+    profile.folderPath = QStringLiteral("Solo");
+    const std::optional<Profile> created = m_repo->createProfile(profile);
+    QVERIFY(created.has_value());
+
+    QVERIFY(m_repo->deleteFolder(QStringLiteral("Solo")));
+    const std::optional<Profile> fetched = m_repo->getProfile(created->id);
+    QVERIFY(fetched.has_value());
+    QCOMPARE(fetched->folderPath, QString());
+}
+
+void TestProfileRepository::deleteFolderShiftsSubfoldersAndTheirProfilesUp()
+{
+    QVERIFY(m_repo->createFolder(QStringLiteral("Work/Servers")));
+
+    Profile inTarget = makeSshProfile(QStringLiteral("InWork"));
+    inTarget.folderPath = QStringLiteral("Work");
+    const std::optional<Profile> createdInTarget = m_repo->createProfile(inTarget);
+    QVERIFY(createdInTarget.has_value());
+
+    Profile inSubfolder = makeRdpProfile(QStringLiteral("InServers"));
+    inSubfolder.folderPath = QStringLiteral("Work/Servers");
+    const std::optional<Profile> createdInSubfolder = m_repo->createProfile(inSubfolder);
+    QVERIFY(createdInSubfolder.has_value());
+
+    QVERIFY(m_repo->deleteFolder(QStringLiteral("Work")));
+
+    // "Work/Servers" shifts up to become root-level "Servers"; the profile
+    // that was directly in "Work" moves to root; nothing is deleted.
+    const auto folders = m_repo->listFolders();
+    QCOMPARE(folders.size(), size_t(1));
+    QCOMPARE(folders[0], QStringLiteral("Servers"));
+
+    const std::optional<Profile> fetchedInTarget = m_repo->getProfile(createdInTarget->id);
+    QVERIFY(fetchedInTarget.has_value());
+    QCOMPARE(fetchedInTarget->folderPath, QString());
+
+    const std::optional<Profile> fetchedInSubfolder = m_repo->getProfile(createdInSubfolder->id);
+    QVERIFY(fetchedInSubfolder.has_value());
+    QCOMPARE(fetchedInSubfolder->folderPath, QStringLiteral("Servers"));
+}
+
+void TestProfileRepository::deleteFolderRejectsEmptyPath()
+{
+    QVERIFY(!m_repo->deleteFolder(QString()));
+    QVERIFY(!m_repo->lastError().isEmpty());
+}
+
+void TestProfileRepository::deleteNonexistentFolderSucceedsAsNoOp()
+{
+    QVERIFY(m_repo->deleteFolder(QStringLiteral("Never/Created")));
+}
+
+QTEST_GUILESS_MAIN(TestProfileRepository)
+#include "test_profile_repository.moc"

tests/test_rdp_session_backend.cpp

@@ -0,0 +1,281 @@
+#include "rdp_session_backend.h"
+
+#include <QTest>
+
+#include <freerdp/error.h>
+#include <freerdp/locale/keyboard.h>
+#include <freerdp/scancode.h>
+
+class TestRdpSessionBackend : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void normalizedRdpSecurityModeRecognizesKnownValues();
+    void normalizedRdpSecurityModeFallsBackToNegotiate();
+    void normalizedRdpPerformanceProfileRecognizesKnownValues();
+    void normalizedRdpPerformanceProfileFallsBackToBalanced();
+    void nearestFreeRdpScaleValueMapsToLegalValues();
+
+    void sanitizeDesktopWidthClampsToLegalRange();
+    void sanitizeDesktopHeightClampsToLegalRange();
+
+    void scancodeFromNativeScanCodeHandlesZero();
+#if defined(Q_OS_LINUX)
+    void scancodeFromNativeScanCodeDelegatesToX11TableOnLinux();
+    void scancodeFromNativeScanCodeDoesNotTreatX11KeycodeAsPcAtScancode();
+#endif
+
+    void scancodeForQtKeyMapsDirectKeys();
+    void scancodeForQtKeyRespectsKeypadModifier();
+    void scancodeForQtKeyDisambiguatesLeftRightModifiers();
+    void scancodeForQtKeyReturnsUnknownForUnhandledKey();
+
+    void mapRdpErrorRecognizesAuthFailureCodes();
+    void mapRdpErrorRecognizesAccountStateCodes();
+    void mapRdpErrorRecognizesNetworkCodes();
+    void mapRdpErrorFallsBackForUnknownCode();
+
+    void isExpectedDisconnectCodeRecognizesBenignCodes();
+    void isExpectedDisconnectCodeRejectsAuthFailure();
+
+    void isExpectedConnectAbortCodeRecognizesCancellation();
+    void isExpectedConnectAbortCodeRejectsAuthFailure();
+
+    void disconnectMessageForCodeRecognizesKnownCodes();
+    void disconnectMessageForCodeFallsBackForUnknownCode();
+
+    void rdpErrorRawIncludesHexCode();
+};
+
+void TestRdpSessionBackend::normalizedRdpSecurityModeRecognizesKnownValues()
+{
+    QCOMPARE(RdpSessionBackend::normalizedRdpSecurityMode(QStringLiteral("nla")),
+             QStringLiteral("NLA"));
+    QCOMPARE(RdpSessionBackend::normalizedRdpSecurityMode(QStringLiteral(" TLS ")),
+             QStringLiteral("TLS"));
+    QCOMPARE(RdpSessionBackend::normalizedRdpSecurityMode(QStringLiteral("Rdp")),
+             QStringLiteral("RDP"));
+}
+
+void TestRdpSessionBackend::normalizedRdpSecurityModeFallsBackToNegotiate()
+{
+    QCOMPARE(RdpSessionBackend::normalizedRdpSecurityMode(QStringLiteral("bogus")),
+             QStringLiteral("Negotiate"));
+    QCOMPARE(RdpSessionBackend::normalizedRdpSecurityMode(QString()),
+             QStringLiteral("Negotiate"));
+}
+
+void TestRdpSessionBackend::normalizedRdpPerformanceProfileRecognizesKnownValues()
+{
+    QCOMPARE(RdpSessionBackend::normalizedRdpPerformanceProfile(QStringLiteral("best quality")),
+             QStringLiteral("Best Quality"));
+    QCOMPARE(RdpSessionBackend::normalizedRdpPerformanceProfile(QStringLiteral(" Best Performance ")),
+             QStringLiteral("Best Performance"));
+    QCOMPARE(RdpSessionBackend::normalizedRdpPerformanceProfile(QStringLiteral("auto detect")),
+             QStringLiteral("Auto Detect"));
+}
+
+void TestRdpSessionBackend::normalizedRdpPerformanceProfileFallsBackToBalanced()
+{
+    QCOMPARE(RdpSessionBackend::normalizedRdpPerformanceProfile(QStringLiteral("bogus")),
+             QStringLiteral("Balanced"));
+}
+
+void TestRdpSessionBackend::nearestFreeRdpScaleValueMapsToLegalValues()
+{
+    // MS-RDPEDISP legally permits only {100, 140, 180} -- anything else is
+    // silently ignored by the server.
+    QCOMPARE(RdpSessionBackend::nearestFreeRdpScaleValue(1.0), quint32(100));
+    QCOMPARE(RdpSessionBackend::nearestFreeRdpScaleValue(1.2), quint32(100));
+    QCOMPARE(RdpSessionBackend::nearestFreeRdpScaleValue(1.25), quint32(140));
+    QCOMPARE(RdpSessionBackend::nearestFreeRdpScaleValue(1.6), quint32(140));
+    QCOMPARE(RdpSessionBackend::nearestFreeRdpScaleValue(2.0), quint32(180));
+    QCOMPARE(RdpSessionBackend::nearestFreeRdpScaleValue(3.0), quint32(180));
+}
+
+void TestRdpSessionBackend::sanitizeDesktopWidthClampsToLegalRange()
+{
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopWidth(0), 1280);
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopWidth(-100), 1280);
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopWidth(100), 640);
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopWidth(1920), 1920);
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopWidth(99999), 8192);
+}
+
+void TestRdpSessionBackend::sanitizeDesktopHeightClampsToLegalRange()
+{
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopHeight(0), 720);
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopHeight(-100), 720);
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopHeight(100), 360);
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopHeight(1080), 1080);
+    QCOMPARE(RdpSessionBackend::sanitizeDesktopHeight(99999), 4320);
+}
+
+void TestRdpSessionBackend::scancodeFromNativeScanCodeHandlesZero()
+{
+    QCOMPARE(RdpSessionBackend::scancodeFromNativeScanCode(0), quint32(RDP_SCANCODE_UNKNOWN));
+}
+
+#if defined(Q_OS_LINUX)
+void TestRdpSessionBackend::scancodeFromNativeScanCodeDelegatesToX11TableOnLinux()
+{
+    // Our wrapper must be a faithful passthrough to FreeRDP's own
+    // authoritative X11-keycode table, not a reimplementation of it.
+    const quint32 apostropheKeycode = 0x30;
+#if defined(__GNUC__) || defined(__clang__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
+    const quint32 expected =
+        static_cast<quint32>(freerdp_keyboard_get_rdp_scancode_from_x11_keycode(apostropheKeycode));
+#if defined(__GNUC__) || defined(__clang__)
+#pragma GCC diagnostic pop
+#endif
+    QCOMPARE(RdpSessionBackend::scancodeFromNativeScanCode(apostropheKeycode), expected);
+}
+
+void TestRdpSessionBackend::scancodeFromNativeScanCodeDoesNotTreatX11KeycodeAsPcAtScancode()
+{
+    // Regression guard for the historical bug this table replaced: X11
+    // keycode 0x30 (apostrophe/quote) must NOT resolve to whatever a naive
+    // "treat the X11 keycode as a PC/AT set-1 scancode" interpretation
+    // would give (PC/AT 0x30 is the B key).
+    const quint32 apostropheKeycode = 0x30;
+    const quint32 naivePcAtInterpretation = MAKE_RDP_SCANCODE(apostropheKeycode, FALSE);
+    QVERIFY(RdpSessionBackend::scancodeFromNativeScanCode(apostropheKeycode)
+            != naivePcAtInterpretation);
+}
+#endif
+
+void TestRdpSessionBackend::scancodeForQtKeyMapsDirectKeys()
+{
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_Escape, Qt::NoModifier, 0),
+             quint32(RDP_SCANCODE_ESCAPE));
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_A, Qt::NoModifier, 0),
+             quint32(RDP_SCANCODE_KEY_A));
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_F1, Qt::NoModifier, 0),
+             quint32(RDP_SCANCODE_F1));
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_Space, Qt::NoModifier, 0),
+             quint32(RDP_SCANCODE_SPACE));
+}
+
+void TestRdpSessionBackend::scancodeForQtKeyRespectsKeypadModifier()
+{
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_Insert, Qt::NoModifier, 0),
+             quint32(RDP_SCANCODE_INSERT));
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_Insert, Qt::KeypadModifier, 0),
+             quint32(RDP_SCANCODE_NUMPAD0));
+
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_Delete, Qt::NoModifier, 0),
+             quint32(RDP_SCANCODE_DELETE));
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_Delete, Qt::KeypadModifier, 0),
+             quint32(RDP_SCANCODE_DECIMAL));
+}
+
+void TestRdpSessionBackend::scancodeForQtKeyDisambiguatesLeftRightModifiers()
+{
+    // With no reliable native scancode (0 -> RDP_SCANCODE_UNKNOWN, which
+    // matches neither side), both Shift and Control must default to their
+    // left variant rather than picking arbitrarily.
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_Shift, Qt::NoModifier, 0),
+             quint32(RDP_SCANCODE_LSHIFT));
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_Control, Qt::NoModifier, 0),
+             quint32(RDP_SCANCODE_LCONTROL));
+}
+
+void TestRdpSessionBackend::scancodeForQtKeyReturnsUnknownForUnhandledKey()
+{
+    QCOMPARE(RdpSessionBackend::scancodeForQtKey(Qt::Key_MediaPlay, Qt::NoModifier, 0),
+             quint32(RDP_SCANCODE_UNKNOWN));
+}
+
+void TestRdpSessionBackend::mapRdpErrorRecognizesAuthFailureCodes()
+{
+    const QString expected = QStringLiteral("Authentication failed. Check username and password.");
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_CONNECT_LOGON_FAILURE), expected);
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_CONNECT_WRONG_PASSWORD), expected);
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_CONNECT_ACCESS_DENIED), expected);
+}
+
+void TestRdpSessionBackend::mapRdpErrorRecognizesAccountStateCodes()
+{
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_CONNECT_ACCOUNT_DISABLED),
+             QStringLiteral("Account is disabled."));
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_CONNECT_ACCOUNT_LOCKED_OUT),
+             QStringLiteral("Account is locked out."));
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_CONNECT_ACCOUNT_EXPIRED),
+             QStringLiteral("Account has expired."));
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_CONNECT_PASSWORD_EXPIRED),
+             QStringLiteral("Password has expired."));
+}
+
+void TestRdpSessionBackend::mapRdpErrorRecognizesNetworkCodes()
+{
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_DNS_NAME_NOT_FOUND),
+             QStringLiteral("Host could not be resolved."));
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_CONNECT_TRANSPORT_FAILED),
+             QStringLiteral("Network transport failed while connecting."));
+    QCOMPARE(RdpSessionBackend::mapRdpError(FREERDP_ERROR_SECURITY_NEGO_CONNECT_FAILED),
+             QStringLiteral("RDP security negotiation failed. Try a different RDP security mode."));
+}
+
+void TestRdpSessionBackend::mapRdpErrorFallsBackForUnknownCode()
+{
+    // Not a code mapRdpError special-cases; must still return something
+    // non-empty rather than crashing or returning an empty string.
+    const QString result = RdpSessionBackend::mapRdpError(0x7FFFFFFF);
+    QVERIFY(!result.isEmpty());
+}
+
+void TestRdpSessionBackend::isExpectedDisconnectCodeRecognizesBenignCodes()
+{
+    QVERIFY(RdpSessionBackend::isExpectedDisconnectCode(FREERDP_ERROR_SUCCESS));
+    QVERIFY(RdpSessionBackend::isExpectedDisconnectCode(FREERDP_ERROR_NONE));
+    QVERIFY(RdpSessionBackend::isExpectedDisconnectCode(FREERDP_ERROR_LOGOFF_BY_USER));
+    QVERIFY(RdpSessionBackend::isExpectedDisconnectCode(FREERDP_ERROR_IDLE_TIMEOUT));
+}
+
+void TestRdpSessionBackend::isExpectedDisconnectCodeRejectsAuthFailure()
+{
+    // An authentication failure must be treated as a real error, never as
+    // an expected/benign disconnect -- otherwise the user would see no
+    // error message at all for a failed login.
+    QVERIFY(!RdpSessionBackend::isExpectedDisconnectCode(FREERDP_ERROR_CONNECT_LOGON_FAILURE));
+}
+
+void TestRdpSessionBackend::isExpectedConnectAbortCodeRecognizesCancellation()
+{
+    QVERIFY(RdpSessionBackend::isExpectedConnectAbortCode(FREERDP_ERROR_CONNECT_CANCELLED));
+    QVERIFY(RdpSessionBackend::isExpectedConnectAbortCode(FREERDP_ERROR_SUCCESS));
+}
+
+void TestRdpSessionBackend::isExpectedConnectAbortCodeRejectsAuthFailure()
+{
+    QVERIFY(!RdpSessionBackend::isExpectedConnectAbortCode(FREERDP_ERROR_CONNECT_LOGON_FAILURE));
+}
+
+void TestRdpSessionBackend::disconnectMessageForCodeRecognizesKnownCodes()
+{
+    QCOMPARE(RdpSessionBackend::disconnectMessageForCode(FREERDP_ERROR_IDLE_TIMEOUT),
+             QStringLiteral("RDP session disconnected due to idle timeout."));
+    QCOMPARE(RdpSessionBackend::disconnectMessageForCode(FREERDP_ERROR_LOGOFF_BY_USER),
+             QStringLiteral("RDP session signed out."));
+    QCOMPARE(RdpSessionBackend::disconnectMessageForCode(FREERDP_ERROR_CONNECT_CANCELLED),
+             QStringLiteral("Connection cancelled."));
+}
+
+void TestRdpSessionBackend::disconnectMessageForCodeFallsBackForUnknownCode()
+{
+    QCOMPARE(RdpSessionBackend::disconnectMessageForCode(0x7FFFFFFF),
+             QStringLiteral("RDP session ended."));
+}
+
+void TestRdpSessionBackend::rdpErrorRawIncludesHexCode()
+{
+    const QString result = RdpSessionBackend::rdpErrorRaw(FREERDP_ERROR_SUCCESS);
+    QVERIFY(result.contains(QStringLiteral("(0x00000000)")));
+}
+
+QTEST_GUILESS_MAIN(TestRdpSessionBackend)
+#include "test_rdp_session_backend.moc"

tests/test_ssh_session_backend.cpp

@@ -0,0 +1,236 @@
+#include "ssh_session_backend.h"
+
+#include <QTest>
+
+#include <memory>
+
+#ifndef ORBITHUB_TEST_FIXTURES_DIR
+#error "ORBITHUB_TEST_FIXTURES_DIR must be defined by the build"
+#endif
+
+namespace {
+Profile makeProfile(const QString& fixtureHost)
+{
+    Profile profile;
+    profile.name = QStringLiteral("Test Profile");
+    profile.host = fixtureHost;
+    profile.port = 22;
+    profile.username = QStringLiteral("tester");
+    profile.protocol = QStringLiteral("SSH");
+    profile.authMode = QStringLiteral("Password");
+    return profile;
+}
+
+SessionConnectOptions makeOptions()
+{
+    SessionConnectOptions options;
+    options.password = QStringLiteral("dummy-password");
+    return options;
+}
+}
+
+class TestSshSessionBackend : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    // Pure-function coverage -- no process involved.
+    void mapSshErrorRecognizesKnownPatterns();
+    void mapSshErrorFallsBackForUnknownText();
+    void mapSshErrorHandlesEmptyInput();
+    void escapeForShellSingleQuotesNeutralizesQuotes();
+    void escapeForShellSingleQuotesLeavesPlainTextAlone();
+
+    // State-machine coverage, driven against tests/fixtures/fake_ssh.sh
+    // instead of a real ssh binary or network.
+    void init();
+    void cleanup();
+    void successfulConnectReachesConnectedThenDisconnects();
+    void authFailureReachesFailedStateWithMappedMessage();
+    void connectionRefusedReachesFailedState();
+    void sendInputEchoesThroughOutputReceived();
+    void reconnectRestartsAndReachesConnectedAgain();
+
+private:
+    QString fixturePath() const;
+    void createBackend(const QString& fixtureHost);
+
+    std::unique_ptr<SshSessionBackend> m_backend;
+    SessionState m_lastState = SessionState::Disconnected;
+    QString m_lastErrorDisplay;
+    QString m_lastErrorRaw;
+    QString m_receivedOutput;
+};
+
+QString TestSshSessionBackend::fixturePath() const
+{
+    return QStringLiteral(ORBITHUB_TEST_FIXTURES_DIR "/fake_ssh.sh");
+}
+
+void TestSshSessionBackend::createBackend(const QString& fixtureHost)
+{
+    m_backend =
+        std::make_unique<SshSessionBackend>(makeProfile(fixtureHost), fixturePath(), nullptr);
+    connect(m_backend.get(),
+            &SessionBackend::stateChanged,
+            this,
+            [this](SessionState state, const QString&) { m_lastState = state; });
+    connect(m_backend.get(),
+            &SessionBackend::connectionError,
+            this,
+            [this](const QString& display, const QString& raw) {
+                m_lastErrorDisplay = display;
+                m_lastErrorRaw = raw;
+            });
+    connect(m_backend.get(),
+            &SessionBackend::outputReceived,
+            this,
+            [this](const QString& chunk) { m_receivedOutput += chunk; });
+}
+
+void TestSshSessionBackend::mapSshErrorRecognizesKnownPatterns()
+{
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("Permission denied (publickey,password).")),
+             QStringLiteral("Authentication failed. Check username and credentials."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("Host key verification failed.")),
+             QStringLiteral("Host key verification failed."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("ssh: Could not resolve hostname bogus")),
+             QStringLiteral("Host could not be resolved."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("ssh: connect to host x port 22: Connection timed out")),
+             QStringLiteral("Connection timed out."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("ssh: connect to host x port 22: Connection refused")),
+             QStringLiteral("Connection refused by remote host."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("ssh: connect to host x port 22: No route to host")),
+             QStringLiteral("No route to host."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("Identity file /nope not accessible: No such file.")),
+             QStringLiteral("Private key file is not accessible."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("posix_spawn: /usr/bin/ssh-askpass: No such file or directory")),
+             QStringLiteral("SSH password helper is missing or failed to launch."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("open /some/other/path: No such file or directory")),
+             QStringLiteral("Required file was not found."));
+}
+
+void TestSshSessionBackend::mapSshErrorFallsBackForUnknownText()
+{
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("some completely novel ssh error text")),
+             QStringLiteral("SSH connection failed."));
+}
+
+void TestSshSessionBackend::mapSshErrorHandlesEmptyInput()
+{
+    QCOMPARE(SshSessionBackend::mapSshError(QString()),
+             QStringLiteral("SSH connection failed for an unknown reason."));
+    QCOMPARE(SshSessionBackend::mapSshError(QStringLiteral("   ")),
+             QStringLiteral("SSH connection failed for an unknown reason."));
+}
+
+void TestSshSessionBackend::escapeForShellSingleQuotesNeutralizesQuotes()
+{
+    // A password containing a single quote must not be able to break out
+    // of the single-quoted printf argument in the askpass script -- this
+    // is the actual security boundary, not just cosmetic escaping.
+    const QString malicious = QStringLiteral("pw' ; rm -rf ~ ; echo '");
+    const QString escaped = SshSessionBackend::escapeForShellSingleQuotes(malicious);
+    const QString reconstructedScriptArg = QStringLiteral("'") + escaped + QStringLiteral("'");
+    // Every single quote in the reconstructed argument must be either the
+    // outer boundary quote (open at index 0, close at the very end) or the
+    // start of a full '"'"' re-opening sequence -- never a bare, unescaped
+    // quote that could close the argument early.
+    int index = 0;
+    while (index < reconstructedScriptArg.length()) {
+        if (reconstructedScriptArg.at(index) != QChar::fromLatin1('\'')) {
+            ++index;
+            continue;
+        }
+        if (index == 0 || index == reconstructedScriptArg.length() - 1) {
+            ++index;
+            continue;
+        }
+        QCOMPARE(reconstructedScriptArg.mid(index, 5), QStringLiteral("'\"'\"'"));
+        index += 5;
+    }
+}
+
+void TestSshSessionBackend::escapeForShellSingleQuotesLeavesPlainTextAlone()
+{
+    QCOMPARE(SshSessionBackend::escapeForShellSingleQuotes(QStringLiteral("plain-password-123")),
+             QStringLiteral("plain-password-123"));
+}
+
+void TestSshSessionBackend::init()
+{
+#ifdef Q_OS_WIN
+    // fixtures/fake_ssh.sh is a POSIX shell script; there's no Windows
+    // fixture yet, so skip only the tests that actually launch it. The
+    // pure-function tests above (mapSshError*, escapeForShellSingleQuotes*)
+    // don't touch the fixture and still run everywhere.
+    const QByteArray currentTest = QTest::currentTestFunction();
+    if (!currentTest.startsWith("mapSshError") && !currentTest.startsWith("escapeForShellSingleQuotes")) {
+        QSKIP("No Windows equivalent of tests/fixtures/fake_ssh.sh yet");
+    }
+#endif
+
+    m_lastState = SessionState::Disconnected;
+    m_lastErrorDisplay.clear();
+    m_lastErrorRaw.clear();
+    m_receivedOutput.clear();
+    // Individual tests call createBackend() with the fixture host they
+    // need; most want "succeed", so provide it as the default here.
+    createBackend(QStringLiteral("succeed"));
+}
+
+void TestSshSessionBackend::cleanup()
+{
+    if (m_backend) {
+        m_backend->disconnectSession();
+    }
+    m_backend.reset();
+}
+
+void TestSshSessionBackend::successfulConnectReachesConnectedThenDisconnects()
+{
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Connected);
+
+    m_backend->disconnectSession();
+    QTRY_COMPARE(m_lastState, SessionState::Disconnected);
+}
+
+void TestSshSessionBackend::authFailureReachesFailedStateWithMappedMessage()
+{
+    createBackend(QStringLiteral("fail-auth"));
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Failed);
+    QCOMPARE(m_lastErrorDisplay, QStringLiteral("Authentication failed. Check username and credentials."));
+    QVERIFY(m_lastErrorRaw.contains(QStringLiteral("Permission denied")));
+}
+
+void TestSshSessionBackend::connectionRefusedReachesFailedState()
+{
+    createBackend(QStringLiteral("refuse"));
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Failed);
+    QCOMPARE(m_lastErrorDisplay, QStringLiteral("Connection refused by remote host."));
+}
+
+void TestSshSessionBackend::sendInputEchoesThroughOutputReceived()
+{
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Connected);
+
+    m_backend->sendInput(QStringLiteral("hello-from-test\n"));
+    QTRY_VERIFY(m_receivedOutput.contains(QStringLiteral("hello-from-test")));
+}
+
+void TestSshSessionBackend::reconnectRestartsAndReachesConnectedAgain()
+{
+    m_backend->connectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Connected);
+
+    m_lastState = SessionState::Connecting;
+    m_backend->reconnectSession(makeOptions());
+    QTRY_COMPARE(m_lastState, SessionState::Connected);
+}
+
+QTEST_GUILESS_MAIN(TestSshSessionBackend)
+#include "test_ssh_session_backend.moc"

third_party/FreeRDP/.source_tag

@@ -0,0 +1 @@
+3.23.1-dev0