Of COURSE that trick wouldn't work on all renderers. Fall back to something for now, hopefully figure out a better way to do this later. If we have to, we can use vertical line and horizontal line textures for vertical and horizontal lines, and then create custom textures for diagonal lines and software render those. It's terrible, but at least it would be pixel perfect.

/**
 * Part of SDL test suite.
 *
 * Written by Edgar Simo "bobbens"
 *
 * Released under Public Domain.
 */


#ifndef _TEST_RENDER
#  define _TEST_RENDER


int test_render (void);


#endif /* _TEST_RENDER */