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Bug 1810 - xxx_RenderReadPixels - incorrect behaviour in certain conditions
Summary: xxx_RenderReadPixels - incorrect behaviour in certain conditions
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: video (show other bugs)
Version: HG 2.0
Hardware: All Other
: P2 normal
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2013-04-18 02:35 UTC by PoopiSan
Modified: 2013-07-12 03:55 UTC (History)
0 users

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Description PoopiSan 2013-04-18 02:35:32 UTC 
GLES2_RenderReadPixels, GLES_RenderReadPixels, GL_RenderReadPixels and possibly other backends is incorrectly implemented.

If the current target viewport is different than window size the function is reading garbage and according to the function documentation should work with any rendering target "Read pixels from the current rendering target.".

this seems to be caused by this line:

...
SDL_GetWindowSize(window, &w, &h);
...

quick fix and change to 


if(renderer->target == NULL)
{
  SDL_GetWindowSize(window, &w, &h);
}
else
{
  w=rect->w;h=rect->h;
}

seem to solve my case ( viewport is equal to texture size, no scaling ).

After this change all textures are read correctly. This function is very useful for texture rendering debugging.
Comment 1 Sam Lantinga 2013-07-12 02:41:36 UTC 
Can you double check this in the current snapshot?
http://www.libsdl.org/tmp/SDL-2.0.zip

I think this was fixed at some point, since the viewport is actually used now:
    real_rect.x = renderer->viewport.x;
    real_rect.y = renderer->viewport.y;
    real_rect.w = renderer->viewport.w;
    real_rect.h = renderer->viewport.h;
Comment 2 Sam Lantinga 2013-07-12 03:55:50 UTC 
Actually, I just ran into this bug myself and fixed it.  Thanks!
http://hg.libsdl.org/SDL/rev/fe82b639c4d6