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Fixed bug 3309 - SDL_ConvertSurface adds AlphaMod when input surface …
…has ColorKey

Sylvain

Let's you have a SDL_Surface that has ColorKey, but no Alpha Modulation.
When this surface is duplicated with SDL_ConvertSurface function, the result has ColorKey and Alpha Modulation (BLEND, and Opaque 255).

I think SDL_ConvertSurface should strictly keeps the input format.


example
=======

SDL_Surface *input; // ... Set up a surface with ColorKey and no AlphaMod

SDL_Surface *output = SDL_ConvertSurface(input, input->format, input->flags);

// "output" surface has a ColorKey but *also* AlphaMod (BLEND, and Opaque 255).
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slouken committed Aug 12, 2017
1 parent e4124ff commit 1a5441451c31c71bd6e673268dcca62cc84f3210
Showing with 1 addition and 1 deletion.
  1. +1 −1 src/video/SDL_surface.c
@@ -986,7 +986,7 @@ SDL_ConvertSurface(SDL_Surface * surface, const SDL_PixelFormat * format,
/* Enable alpha blending by default if the new surface has an
* alpha channel or alpha modulation */
if ((surface->format->Amask && format->Amask) ||
(copy_flags & (SDL_COPY_COLORKEY|SDL_COPY_MODULATE_ALPHA))) {
(copy_flags & SDL_COPY_MODULATE_ALPHA)) {
SDL_SetSurfaceBlendMode(convert, SDL_BLENDMODE_BLEND);
}
if ((copy_flags & SDL_COPY_RLE_DESIRED) || (flags & SDL_RLEACCEL)) {

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