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Bug 4026 - SDL_RenderClear() with transparency doesn't work
Summary: SDL_RenderClear() with transparency doesn't work
Status: RESOLVED INVALID
Alias: None
Product: SDL
Classification: Unclassified
Component: render (show other bugs)
Version: 2.0.7
Hardware: x86_64 Linux
: P2 normal
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2018-01-06 11:45 UTC by Ellie
Modified: 2018-09-12 08:51 UTC (History)
1 user (show)

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Description Ellie 2018-01-06 11:45:32 UTC 
According to the documentation, SDL_RenderClear() will "clear the current rendering target with the drawing color". Therefore, the following code should intuitively clear the render target with transparency:

        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0);
        SDL_RenderClear(renderer);

However, the result in my tests is a black color. This user seems to have identified some relation to blend modes:

 https://forums.libsdl.org/viewtopic.php?p=39909

Since SDL_RenderClear() is not intended for blending on top and the documentation makes no mention of blend modes but clearly suggests that the color is replaced unconditionally with the specified render color, I think this is a bug that should be fixed.
Comment 1 Ellie 2018-01-06 12:05:23 UTC 
Oops, I was running it on a completely invalid memory address and for some divine reason it didn't crash (but it also didn't work, unsurprisingly). Sorry :-)