[Scummvm-tracker] [ScummVM :: Bugs] #15151: BACKENDS: OPENGL: Alpha channel changes cause color regression on PowerBook G4

[ScummVM :: Bugs]

#15151: BACKENDS: OPENGL: Alpha channel changes cause color regression on PowerBook
G4
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Reporter:  dwatteau  |       Owner:  (none)
    Type:  defect    |      Status:  new
Priority:  normal    |   Component:  Graphics
 Version:            |  Resolution:
Keywords:            |        Game:
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Comment (by dwatteau):

 FWIW, as suggested by lephilousophe, doing this change in
 `backends/graphics/opengl/framebuffer.cpp`:

 {{{
                 case kBlendModeOpaque:
                         GL_CALL(glEnable(GL_BLEND));
 -                       GL_CALL(glBlendColor(1.f, 1.f, 1.f, 0.f));
 +                       GL_CALL(glBlendColor(1.f, 1.f, 0.f, 1.f));
                         GL_CALL(glBlendFunc(GL_CONSTANT_COLOR,
 GL_ONE_MINUS_CONSTANT_COLOR));
                         break;
 }}}

 or using `glBlendColor(1.f, 1.f, 1.f, 1.f)`, make the color problem go
 away. Putting a value of `0.f` for the red or green parameters doesn't fix
 the issue, however.

 I see that both my Debian and OpenBSD systems use the same Mesa release;
 I'll try updating one of them to Mesa 23.x to see if it fixes anything.
-- 
Ticket URL: <https://bugs.scummvm.org/ticket/15151#comment:1>
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