Apply HiDPI scaling to quads

The anti-aliasing strategy is pretty naive, but we will manage for now.

wgpu/src/shader/quad.frag

@@ -3,7 +3,7 @@
 layout(location = 0) in vec4 v_Color;
 layout(location = 1) in vec2 v_Pos;
 layout(location = 2) in vec2 v_Scale;
-layout(location = 3) in flat uint v_BorderRadius;
+layout(location = 3) in float v_BorderRadius;
 
 layout(location = 0) out vec4 o_Color;
 
@@ -27,11 +27,7 @@ float rounded(in vec2 frag_coord, in vec2 position, in vec2 size, float radius,
 }
 
 void main() {
-    float radius_alpha = 1.0;
-
-    if(v_BorderRadius > 0.0) {
-        radius_alpha = rounded(gl_FragCoord.xy, v_Pos, v_Scale, v_BorderRadius, 0.5);
-    }
+    float radius_alpha = rounded(gl_FragCoord.xy, v_Pos, v_Scale, v_BorderRadius, 0.5);
 
     o_Color = vec4(v_Color.xyz, v_Color.w * radius_alpha);
 }

wgpu/src/shader/quad.vert

@@ -4,29 +4,33 @@ layout(location = 0) in vec2 v_Pos;
 layout(location = 1) in vec2 i_Pos;
 layout(location = 2) in vec2 i_Scale;
 layout(location = 3) in vec4 i_Color;
-layout(location = 4) in uint i_BorderRadius;
+layout(location = 4) in float i_BorderRadius;
 
 layout (set = 0, binding = 0) uniform Globals {
     mat4 u_Transform;
+    float u_Scale;
 };
 
 layout(location = 0) out vec4 o_Color;
 layout(location = 1) out vec2 o_Pos;
 layout(location = 2) out vec2 o_Scale;
-layout(location = 3) out uint o_BorderRadius;
+layout(location = 3) out float o_BorderRadius;
 
 void main() {
+    vec2 p_Pos = i_Pos * u_Scale;
+    vec2 p_Scale = i_Scale  * u_Scale;
+
     mat4 i_Transform = mat4(
-        vec4(i_Scale.x, 0.0, 0.0, 0.0),
-        vec4(0.0, i_Scale.y, 0.0, 0.0),
+        vec4(p_Scale.x + 1.0, 0.0, 0.0, 0.0),
+        vec4(0.0, p_Scale.y + 1.0, 0.0, 0.0),
         vec4(0.0, 0.0, 1.0, 0.0),
-        vec4(i_Pos, 0.0, 1.0)
+        vec4(p_Pos - vec2(0.5, 0.5), 0.0, 1.0)
     );
 
     o_Color = i_Color;
-    o_Pos = i_Pos;
-    o_Scale = i_Scale;
-    o_BorderRadius = i_BorderRadius;
+    o_Pos = p_Pos;
+    o_Scale = p_Scale;
+    o_BorderRadius = i_BorderRadius * u_Scale;
 
     gl_Position = u_Transform * i_Transform * vec4(v_Pos, 0.0, 1.0);
 }