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Bug 4998

Summary: OpenGL renderer doesn't always enable GL_TEXTURE_2D
Product: SDL Reporter: Juha Niemimäki <juha.niemimaki>
Component: renderAssignee: Ryan C. Gordon <icculus>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 Keywords: target-2.0.14
Version: HG 2.1   
Hardware: PowerPC   
OS: AmigaOS   

Description Juha Niemimäki 2020-02-21 08:10:59 UTC 
It seems that when SDL_UpdateTexture() is called in a draw loop, GL_TEXTURE_2D gets disabled. This issue may only impact platforms without shaders.

A potential workaround is to add glEnable(data->textype) in SetCopyState:

http://hg.libsdl.org/SDL/file/28fcb5ef7ff1/src/render/opengl/SDL_render_gl.c#l1115

Can be reproduced on Linux when shaders are deactivated.
Comment 1 Ryan C. Gordon 2020-03-20 20:47:32 UTC 
So this is cached state, so if we're turning it on and off, we need to check/update:

GL_RenderData::drawstate.texturing

It looks like several places (not just SDL_UpdateTexture) enable and disable it. This is likely a holdover from before we were aggressively caching state.

I need to go back and read up on the legacy rules of GL_TEXTURE_2D...I suspect we don't need to enable it every time we bind a texture, but only when drawing with one, which would mean the correct thing to do is remove all these enable/disable calls outside of the one in SetDrawState().

--ryan.
Comment 2 Ryan C. Gordon 2020-03-22 18:34:03 UTC 
Ok, this is fixed by https://hg.libsdl.org/SDL/rev/1c73cc1e4a3a ...we don't need to enable GL_TEXTURE_* to change texture state, just to enable texturing during rendering.

--ryan.