gpu: pack 2D transforms in vec4 values

Instead of separate 2d scale and transform, pack them into a single
4d value.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/shaders/blit.vert

@@ -5,11 +5,9 @@
 precision highp float;
 
 layout(binding = 0) uniform Block {
+	vec4 transform;
+	vec4 uvTransform;
 	float z;
-	vec2 scale;
-	vec2 offset;
-	vec2 uvScale;
-	vec2 uvOffset;
 };
 
 layout(location = 0) in vec2 pos;
@@ -19,9 +17,7 @@ layout(location = 1) in vec2 uv;
 layout(location = 0) out vec2 vUV;
 
 void main() {
-	vec2 p = pos;
-	p *= scale;
-	p += offset;
+	vec2 p = pos*transform.xy + transform.zw;
 	gl_Position = vec4(p, z, 1);
-	vUV = uv*uvScale + uvOffset;
+	vUV = uv*uvTransform.xy + uvTransform.zw;
 }