[KnifeLemon]

Summary

Sometimes, after double-clicking the tray icon several times, two main windows were open at once.

• Cause: Avalonia's Windows tray raises Clicked synchronously from its window procedure (WM_TRAYMOUSE → OnClicked, not posted). ShowMain only set _main after building the view model, the window, the restored placement and the restored page. A tray click handled during that work re-entered ShowMain, saw _main == null and built a second window. The outer call then overwrote _main, so the first window became an orphan that nothing tracked. After the first trip to the tray the build path is longer (placement and last page, e.g. Theme), which fits the bug showing up mid-session rather than on a fresh start.
• A click that arrived while a window that went to the tray was being closed for good (the posted release, issue Reduce background memory footprint: ~177 MB in the tray, ~500 MB after conversions #119) re-showed that dying window instead of opening a new one, leaving no window.
• Fix (WindowService.ShowMain):
  • A flag marks that a window is being built. Calls made meanwhile go to that window and keep the page they asked for.
  • A tracked window that is being released (or is already closed) is left to close, and a new one opens.
  • ShowMain keeps a list of every main window it built that isn't closed yet. Any other still alive goes to the tray (and is released), so there is never more than one main window.
• MainWindow exposes IsReleased and clears _releasing again if the release close is cancelled.
• Placement restore and releasing the window's memory when it goes to the tray (Reduce background memory footprint: ~177 MB in the tray, ~500 MB after conversions #119) stay as they were.

Test plan

• New SingleMainWindowTests (headless). All three fail on main and pass with the fix:
  • a tray click handled while the window is built, after a few tray round trips (restored Theme page), with and without a page
  • a tray click while the released window closes
  • seeded random sequences of single and double clicks, title-bar closes, HideToTray, pumped and unpumped, with clicks injected during build and release (3 seeds)
• MainWindowReleaseTests, CloseActionTests, TrayServiceTests, WhatsNewTests, ToolbarEditorTests, ThemePageTests pass
• dotnet format Filee.slnx --verify-no-changes, build
• Windows: double-click the tray icon repeatedly across several close-to-tray cycles; only one window ever appears

🤖 Generated with Claude Code