Cleaned up UI renderer a little and added color parameter for quads (WIP).

assets/shaders/glsl/ui.vert

@@ -12,13 +12,20 @@ in vec2 i_position;
 layout(location = 1)
 in vec2 i_texCoord;
 
+layout(location = 2)
+in vec4 i_color;
+
 layout(location = 0)
 out vec2 o_texCoord;
 
+layout(location = 1)
+out vec4 o_color;
+
 void main()
 {
     vec2 relativePos = 2.0 * (i_position / u_windowSize) - vec2(1.0);
     relativePos.y *= -1.0;
     gl_Position = vec4(relativePos, 0.0, 1.0);
     o_texCoord = i_texCoord;
+    o_color = i_color;
 }