Automatic overlay inspection

Reference: pinned TortoiseGit 7338078f8ddd924b8cddee35f512f2286072136d, src/TortoiseIDiff/PicWindow.cpp, PicWindow.h and TortoiseIDiff.rc. This family completes the related overlay controls and temporal comparison flow; it does not change image decoding, Git operations or conflict-side selection.

Source controls and native behavior

PicWindow.cpp:397–410 distinguishes an ordinary alpha-button click from BN_DOUBLECLICKED. A normal click kills ID_ALPHATOGGLETIMER and calls ToggleAlpha: every nonzero alpha becomes zero, then zero becomes one. The double-click notification presses the button and starts a 1,000 ms timer. Its callback (459–462) calls the same endpoint toggle. The first click of an actual double-click sequence has already applied the ordinary toggle; starting the clock does not invent another immediate change.

The native image viewer now uses an actual NSButton with the existing original alpha-toggle artwork. Its native mouse-down distinguishes the second click; ordinary target/action and accessibility activation stop the clock and toggle. Automatic state has a pressed native appearance and an accessible On/Off value. The model owns the one-second task and checks its generation, exact window, current image command owner, overlay/Alpha mode and modal availability before any tick or control response. Native text editing and other windows retain their own input routing. No global event monitor is installed.

The image model owns a weak subscription to comparison-owner changes, delivered on the main scheduler after the owner fields change. This refreshes native button/slider enabled state when an operation ends without changing alpha or restarting timers. Retirement cancels the subscription; dynamic action and timer guards remain authoritative during the operation.

The shared comparison host disables automatic sizing and reapplies its explicit 800×440 content minimum on owned layout/appearance callbacks when needed. Disabling automatic sizing alone was insufficient: hosting attachment could still clear the minimum. Without lifecycle ownership, hosting layout overwrote the minimum with 66×142, allowing a severely cropped image window. The native fixture checks the actual minimum after loading and resizing, then captures it.

Source keyboard alpha commands and slider changes do not kill the source timer. The native model retains that behavior: Space/arrow commands, the 17-position slider and Control-Shift-wheel can change alpha while blinking remains armed. A normal button click is the explicit stop-and-toggle action. Repeated start replaces the previous generation, so an already scheduled callback cannot toggle the replacement clock.

PositionTrackBar (63–80) sizes the vertical alpha channel to the image pane. The native channel now grows and shrinks with its pane instead of keeping a fixed 180-point height. Its top endpoint remains the first image, the bottom the second, with the existing immediate click/drag behavior and 17 positions. Live slider help follows the source %i%% alpha; button help uses the pinned three-line percentage/click/double-click text (TortoiseIDiff.rc:273 and PicWindow.cpp:475–489). The native alpha row keeps its compact percentage label and original image icon in light and dark appearance.

HasMultipleImages (1501–1504) returns false when a second picture is overlaid. The source button layout (1477–1493) therefore hides frame/navigation/player controls in overlay mode. Native controls now follow this rule, and the model also refuses retained Previous/Next/Play actions while overlay is active. Entering overlay stops both frame players as before. Returning to separate panes restores frame controls at the retained frame; it does not restart playback. Conflict panes remain independent and do not gain overlay controls.

Timer and window ownership

Both frame and blink tasks stop when an input is replaced or dropped, when the image view is removed, when an owned sheet starts, when the viewer closes or when the application receives its termination notification. Close/termination also detach the timer window. Old button/slider callbacks revalidate the exact window; dismantled controls clear their targets and actions. The frame tick now revalidates command availability too. Pending task cancellation drains without holding the image model or source bytes indefinitely. Display-only timers do not block ordinary application Quit or acquire repository/file mutation leases.

Stopping hidden alpha blinking on XOR/overlay exit and stopping display timers for an owned modal sheet are explicit macOS ownership adaptations. The pinned Windows handler can leave its alpha timer running while those controls are hidden. This port stops that work and never silently resumes it when the mode or sheet returns. The selected alpha and normal blend mode remain unchanged. Underlying image bytes, animation formats, source frame delays, frame-index policy, native background colors and existing zoom/pan behavior remain intact.

Grouped verification and limits

The cached native receiver adds scripts/test-image-command-family.py --only overlay. It creates private two-frame/three-frame GIF files, preferences and a Git repository, and exercises the actual native button/slider targets and second-click mouse-down. Assertions cover delayed real ticks, pressed state, actual endpoint pixels, manual stop, live percentage help, resize geometry, retained frame controls, XOR return, sheet ownership, busy owner fencing, actual drop/reload, Quit notification, window retirement and task drain. HEAD, raw index and both original GIF byte streams must remain unchanged. Every owned window/sheet is offscreen or invisible, and failure cleanup closes those owners. --captures deliberately permits brief owned light/dark visual acceptance using the existing current-process capture path, then hides the window.

The final Debug application passed all eight affected native pairs: overlay, frames, toolbar and pointer cases with both system and bundled Git. The overlay case verifies the actual minimum after load and resize; its light/dark captures were inspected at that minimum, with the full toolbar, slider and footer fitting. Retained comparison/selection toolbar captures were also inspected in both appearances. All eight owned receiver processes were reaped. Focused repair attempts before these final passes exposed and corrected owner-enabled-state publication and hosting minimum ownership; their failures remain in the QA logs. The batch evidence records all attempts and focused repairs. No Core suite was rerun for this native-only family. Physical double-click timing, all trackpads, VoiceOver announcement, high-contrast appearance and signed minimum-OS/App Store acceptance remain separate requirements. No whole-viewer or whole-application completion claim follows from this family.