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Bug 3870

Summary: opengles2 renderer by default do rgb/bgr conversion
Product: SDL Reporter: Sylvain <sylvain.becker>
Component: *don't know*Assignee: Ryan C. Gordon <icculus>
Status: RESOLVED INVALID QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2    
Version: don't know   
Hardware: All   
OS: All   
Attachments: patch

Description Sylvain 2017-10-10 18:03:05 UTC 
For a texture that has a format SDL_PIXELFORMAT_ARGB8888 (default, as texture_format[0]), opengles2 renderer selects a gl format "GL_RGBA" in GLES2_CreateTexture(). This parameter is used for loading the pixels data with glTexImage2D().
But this leads to have a fragment shader that have to swap r/b.
This is the default path that does swapping for each RenderCopy.

Event if we don't notice anything, could this has a (very) little performance impact ?

Other renderers: 
opengl render uses format = GL_BGRA. 
D3D11 is also using DXGI_FORMAT_B8G8R8A8_UNORM.

maybe opengles2 renderer should also use GL_BGRA and do no swapping in his shader.
Comment 1 Sylvain 2017-10-11 09:34:50 UTC 
Created attachment 2974 [details]
patch

In openGLES2, GL_BGRA_EXT depends on the extension GL_EXT_texture_format_BGRA8888.

Here's the patch I thought to submit, to use minimal shader path.
I tested both on desktop and android device. But I see no fps improvements.
So just discarding it, and closing the issue.
Comment 2 Sylvain 2017-10-11 09:35:23 UTC 
Closing as invalid.