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Bug 1586

Summary: SDL_LockTexture has inconsistent behaviour with different render drivers
Product: SDL Reporter: Pallav Nawani <pallavnawani>
Component: videoAssignee: Sam Lantinga <slouken>
Status: RESOLVED WONTFIX QA Contact: Sam Lantinga <slouken>
Severity: major    
Priority: P2    
Version: HG 2.0   
Hardware: All   
OS: All   

Description Pallav Nawani 2012-08-27 04:38:05 UTC 
Under OpenGL, SDL_LockTexture () provides access to potentially random data from system RAM. Under Direct3D, SDL_LockTexture() does actually provide access to Texture Data.

In particular this sequence will completely clobber the texture data under OpenGL:

SDL_LockTexture();
SDL_UnlockTexture();

While it will work fine under Direct3D.

This bug just caused me 3 wasted days >/
Comment 1 Sam Lantinga 2012-09-28 03:30:40 UTC 
This is an intentional optimization to make streaming textures as fast as possible.
The documentation on the wiki has been clarified:
http://wiki.libsdl.org/moin.cgi/SDL_LockTexture

Thanks!