Added code to fallback to Yosemite or pre-Yosemite system font in case current system font can't be found or is in an unusable format. San Francisco font used on current OS X versions is in a .otf file whih presumably means it has CFF outlines that stb_truetype can't use.

#version 110

attribute vec2 pos;
varying vec2 texcoord;
uniform float width, height;

void main()
{
	gl_Position = vec4(pos, 0.0, 1.0);
	texcoord = sign(pos) * vec2(width/1024.0, height/-1024.0) + vec2(width/1024.0, height/1024.0);
}