Font alignment

Author: mhochsteger

webgpu/shaders/font.wgsl

@@ -12,7 +12,7 @@ struct FontUniforms {
 fn fontGetTexCoord(char: u32, vertexId: u32) -> vec2<f32> {
     return vec2<f32>(
         f32((char - 32) * u_font.width),
-        f32(u_font.height)
+        f32(u_font.height-1)
     );
 }
 
@@ -25,7 +25,7 @@ struct FontFragmentInput {
 fn fragmentFont(@location(0) tex_coord: vec2<f32>) -> @location(0) vec4<f32> {
     let alpha: f32 = textureLoad(
         u_font_texture,
-        vec2i(floor(tex_coord)),
+        vec2i(tex_coord+0.5),
         0
     ).x;
 
@@ -47,7 +47,7 @@ fn fontCalc(char: u32, position: vec4<f32>, vertexId: u32) -> FontFragmentInput
 
     if vertexId == 1 || vertexId == 2 || vertexId == 4 {
         p.x += u_font.width_normalized * p.w;
-        tex_coord.x += f32(u_font.width);
+        tex_coord.x += f32(u_font.width-1);
     }
   return FontFragmentInput(p, tex_coord);
 }

webgpu/shaders/text.wgsl

@@ -56,5 +56,14 @@ fn vertexText(@builtin(vertex_index) vertexId: u32, @builtin(instance_index) cha
     position.x += w * shift.x * f32(text.length);
     position.y += h * shift.y;
 
+    // snap position to pixel grid
+    let resolution = vec2f(f32(u_font.width), f32(u_font.height)) / vec2f(u_font.width_normalized, u_font.height_normalized);
+    let ndc = position.xy / position.w;
+    let screen = (ndc * 0.5 + vec2f(0.5)) * resolution;
+    let snapped_screen = floor(screen) + 0.5;
+    let snapped_ndc = (snapped_screen / resolution - vec2f(0.5)) * 2.0;
+    position.x = snapped_ndc.x * position.w;
+    position.y = snapped_ndc.y * position.w;
+
     return fontCalc(text.char, position, vertexId);
 }