internal/builtinshader: move a clearing shader to builtinshader

internal/atlas/shader.go

@@ -104,13 +104,7 @@ func init() {
 		return nil
 	})
 	wg.Go(func() error {
-		ir, err := graphics.CompileShader([]byte(`//kage:unit pixels
+		ir, err := graphics.CompileShader([]byte(builtinshader.ClearShaderSource))
-
-package main
-
-func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
-	return vec4(0)
-}`))
 		if err != nil {
 			return fmt.Errorf("atlas: compiling the clear shader failed: %w", err)
 		}

internal/builtinshader/shader.go

@@ -188,3 +188,12 @@ func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
 	return mix(mix(c0, c1, rate.x), mix(c2, c3, rate.x), rate.y)
 }
 `)
+
+var ClearShaderSource = []byte(`//kage:unit pixels
+
+package main
+
+func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
+	return vec4(0)
+}
+`)