Image transparent colors and local appearance

Reference: pinned TortoiseGit 7338078f8ddd924b8cddee35f512f2286072136d, TortoiseIDiff/MainWindow.cpp ID_VIEW_TRANSPARENTCOLOR, ID_VIEW_DARKMODE and SetTheme, PicWindow.cpp GetTransparentThemedColor, the two View menu resources and Utils/Theme.cpp GetThemeColor.

Comparison and conflict View menus provide “Transparent color…” and “Dark Mode”. The native owned sheet contains an AppKit color well with OK/Cancel. Only OK commits the selected opaque RGB color; Cancel retains the prior value. All panes in the same image window share one presentation model. The selected color fills transparent image pixels and the canvas, including alpha and XOR composition.

Dark Mode and the unmodified D key switch the containing image window between native Aqua and Dark Aqua. They do not change the application's appearance or other open windows. The containing application replaces a standalone image-diff process, so this preserves independent viewer behavior. Theme switching clears the custom transparency color for all panes, matching upstream SetTheme. White uses the macOS text background in dark appearance; other custom colors use the existing source CTheme HSL conversion. Default colors follow native appearance. The chooser stores the original RGB value rather than its themed projection.

Owned sheets and generation fences prevent a retired window's response from changing its model. Native close/key routing is fenced while a sheet is attached. Selection color is session-local; the source does not persist it. Reloading comparison content retains the window-owned chosen RGB color, matching SetPic. Pane updates retain an attached chooser; pane retirement cancels its pending response, and a newly loaded pane reattaches to the owning presentation. The source resource's B accelerator refers to ID_VIEW_BACKGROUNDCOLOR without a matching MainWindow command case; no unimplemented behavior is claimed for that entry.

Verification and remaining work

The final native receiver passed with system and bundled Git. It exercised actual color wells and OK/Cancel sheet buttons, transparent-pixel raster colors in both comparison panes and three conflict panes, alpha/XOR composition, native D-key routing and appearance reset. Same-window native swatches account for the display profile; a fixed source HSL RGB result checks custom dark colors. Close/Quit guards, chooser survival across native view updates, color retention across source reload and retirement of a pending chooser also passed. Comparison HEAD/raw index/image bytes and conflict raw index/working bytes stayed unchanged. Native light/dark captures were visually inspected. Existing comparison/player regressions passed with both engines, including original slider/keyboard/XOR behavior and multi-frame conflict selection. Final unsigned Debug and AppStore builds and bundle audits passed, including all 116 original icon resources and the required AppStore runtimes. These checks do not establish signing, sandbox runtime acceptance or App Review eligibility. See the QA record. Physical color-picker gestures and focus return, VoiceOver, high contrast and exact Windows/macOS color-management matching remain incomplete. Standalone Load Images is now implemented; see Open parity. Full image and application parity and signed App Store/Finder acceptance remain open.