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Windows transparent margins composite as black: bundled GLFW redirection alpha is uninitialized

Aperta
  • Qualcosa non va?
#109 1 commento 0 reazioni 0 assegnatari Vedi su GitHub

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@Linductor-alkaid ci sta già lavorando.

Dal 14/10/2026.

  • #112 di @Linductor-alkaid — aperta

Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
22/100
Tipo di issue
Bug
Chiarezza
Abbastanza chiara
Stato di attività
Attiva
Stack tecnologico
cpp
Ambito
computer-graphics, desktop

Direzione di ricerca

Start with the bundled GLFW 3.4 Win32 windowProc, specifically the WM_PAINT branch, and compare it with the upstream fix in glfw/glfw#2815 that is referenced in the issue. Then run the transparent_window_viewer fixture on Windows and check the corner RGBA values. Done means the transparent margin shows the desktop instead of black, opaque windows are unchanged, and the four backend Release build/test checks pass. The work is already in progress by the author, so coordinate before starting.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Reproduction

Windows 11 build 26200, NVIDIA RTX 3070 Ti Laptop GPU, driver 32.0.15.9174, MSVC 19.44 x64. EUI dev 89c2d0f.
Build and launch the GLFW/OpenGL transparent_window_viewer fixture. Its 36px outer margin intermittently becomes black even though framebufferTransparent is true. The user confirmed black margins on the actual desktop. Mirage reproduces black rounded corners with the same dependency.

Confirmed isolation and repair

Instrumenting the actual fixture reports corner RGBA=0,0,0,0 with glGetError=0. Clearing the GL default framebuffer was an initial hypothesis; it did not reliably fix the real fixture and has been discarded. A controlled compositor test can also pass on the old code when DWM's backing allocation happens to be zeroed, which explains the intermittent behavior.

The missing initialization is in GLFW's Win32 DWM redirection surface, independently of GL framebuffer alpha. GLFW already tracks this issue in https://github.com/glfw/glfw/issues/2816 and proposed fix https://github.com/glfw/glfw/pull/2815. The bundled 3.4 windowProc has only a damage notification for WM_PAINT and does not define that surface's alpha.

Backporting the small transparent-only WM_PAINT PatBlt(BLACKNESS) repair restores actual desktop transparency on this machine: the formerly black outer margin now shows the wallpaper and desktop icons. Opaque window handling, renderer framebuffer and application geometry stay unchanged; no region crop or color key is used.

A compositor regression uses an owned known-color background and cached UI rendering. Four backend Release build/test checks and relevant fixture inspection are in progress. The separate existing Windows SDL2 compilation blocker is tracked in #110 so it can be reviewed independently.

Lingua principale
C++
Stelle
2k
Fork
177
Merge medio
19h 58m
PR unite (30g)
9

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