Minor edits

crates/render/shaders/ui.wgsl

@@ -33,12 +33,12 @@ var sampler_array: binding_array<sampler>;
 
 // INCLUDE: anchor.wgsl
 
-@vertex
-fn vertex_main(
-	vertex: VertexInput,
-	instance: InstanceInput,
-) -> VertexOutput {
 
+fn transform_vertex(
+	instance: InstanceInput,
+	vertex_position: vec3<f32>,
+	texture_index: u32,
+) -> vec4<f32> {
 	
 	let window_dim = global_data.window_size / global_data.window_scale.x;
 	let scale = instance.size / window_dim.y;
@@ -50,8 +50,8 @@ fn vertex_main(
 	// Apply scale and sprite aspect
 	// Note that our mesh starts centered at (0, 0). This is important!
 	var pos: vec2<f32> = vec2(
-		vertex.position.x * scale * aspect,
-		vertex.position.y * scale
+		vertex_position.x * scale * aspect,
+		vertex_position.y * scale
 	);
 
 	// Apply rotation (and adjust sprite angle, since sprites point north)
@@ -72,10 +72,27 @@ fn vertex_main(
 		vec2(instance.size * aspect, instance.size)
 	);
 
-	var out: VertexOutput;
-	out.position = vec4<f32>(pos, 1.0, 1.0);
-	out.color_transform = instance.color_transform;
+	return vec4<f32>(pos, 0.0, 1.0);
+}
 
+@vertex
+fn vertex_main(
+	vertex: VertexInput,
+	instance: InstanceInput,
+) -> VertexOutput {
+
+	// TODO: this will break if we try to use texture 0.
+	// implement animations for ui sprites & fix that here.
+
+	let pos = transform_vertex(
+		instance,
+		vertex.position,
+		instance.texture_index.x,
+	);
+
+	var out: VertexOutput;
+	out.position = pos;
+	out.color_transform = instance.color_transform;
 
 
 	// TODO: function to get texture from sprite
@@ -108,7 +125,6 @@ fn vertex_main(
 		out.mask_index = vec2(0u, 0u);
 	}
 
-
 	return out;
 }