initial commit

src/glyph_shader.wgsl

@@ -0,0 +1,48 @@
+// Glyph rendering shader for terminal emulator
+
+struct VertexInput {
+    @location(0) position: vec2<f32>,
+    @location(1) uv: vec2<f32>,
+    @location(2) color: vec4<f32>,
+    @location(3) bg_color: vec4<f32>,
+}
+
+struct VertexOutput {
+    @builtin(position) clip_position: vec4<f32>,
+    @location(0) uv: vec2<f32>,
+    @location(1) color: vec4<f32>,
+    @location(2) bg_color: vec4<f32>,
+}
+
+@vertex
+fn vs_main(in: VertexInput) -> VertexOutput {
+    var out: VertexOutput;
+    out.clip_position = vec4<f32>(in.position, 0.0, 1.0);
+    out.uv = in.uv;
+    out.color = in.color;
+    out.bg_color = in.bg_color;
+    return out;
+}
+
+@group(0) @binding(0)
+var atlas_texture: texture_2d<f32>;
+@group(0) @binding(1)
+var atlas_sampler: sampler;
+
+@fragment
+fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
+    // If UV is at origin (0,0), this is a background-only quad
+    let is_background_only = in.uv.x == 0.0 && in.uv.y == 0.0;
+    
+    if is_background_only {
+        // Just render the background color (fully opaque)
+        return in.bg_color;
+    }
+    
+    // Sample the glyph alpha from the atlas
+    let glyph_alpha = textureSample(atlas_texture, atlas_sampler, in.uv).r;
+    
+    // Output foreground color with glyph alpha for blending
+    // The background was already rendered, so we just blend the glyph on top
+    return vec4<f32>(in.color.rgb, in.color.a * glyph_alpha);
+}