static const char *demo_vshader_glsl =
"uniform mat4 u_matViewProjection;\n"
"\n"
"attribute vec4 a_glyph_vertex;\n"
"\n"
"varying vec4 v_glyph;\n"
"\n"
"vec4\n"
"glyph_vertex_transcode (vec2 v)\n"
"{\n"
"  ivec2 g = ivec2 (v);\n"
"  ivec2 corner = ivec2 (mod (v, 2.));\n"
"  g /= 2;\n"
"  ivec2 nominal_size = ivec2 (mod (vec2(g), 64.));\n"
"  return vec4 (corner * nominal_size, g * 4);\n"
"}\n"
"\n"
"void\n"
"main()\n"
"{\n"
"  gl_Position = u_matViewProjection * vec4 (a_glyph_vertex.xy, 0, 1);\n"
"  v_glyph = glyph_vertex_transcode (a_glyph_vertex.zw);\n"
"}\n"
;