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Clarified SDL_RenderReadPixels() documentation

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Clarified that the rect to be read is clipped against the current viewport, not actually relative to it.

Also added a note for people using SDL_SetRenderLogicalPresentation() so they know they have to map between logical space and render space if they want to read back.
This commit is contained in:
Sam Lantinga 2025-02-25 10:25:17 -08:00
parent 2f77558bad
commit 29df99ee38
1 changed files with 5 additions and 3 deletions
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8
include/SDL3/SDL_render.h
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@ -2247,15 +2247,17 @@ extern SDL_DECLSPEC bool SDLCALL SDL_RenderGeometryRaw(SDL_Renderer *renderer,
/**
* Read pixels from the current rendering target.
*
* The returned surface should be freed with SDL_DestroySurface()
* The returned surface contains pixels inside the desired area clipped to the current viewport, and should be freed with SDL_DestroySurface().
*
* Note that this returns the actual pixels on the screen, so if you are using logical presentation you should use SDL_GetRenderLogicalPresentationRect() to get the area containing your content.
*
* **WARNING**: This is a very slow operation, and should not be used
* frequently. If you're using this on the main rendering target, it should be
* called after rendering and before SDL_RenderPresent().
*
* \param renderer the rendering context.
* \param rect an SDL_Rect structure representing the area in pixels relative
* to the to current viewport, or NULL for the entire viewport.
* \param rect an SDL_Rect structure representing the area to read, which will be clipped to the current viewport,
* or NULL for the entire viewport.
* \returns a new SDL_Surface on success or NULL on failure; call
* SDL_GetError() for more information.
*