internal: add comments

internal/atlas/image.go

@@ -156,6 +156,7 @@ const (
 	// A screen image is also unmanaged.
 	ImageTypeScreen
 
+	// ImageTypeVolatile is a volatile image that is cleared every frame.
 	ImageTypeVolatile
 
 	// ImageTypeUnmanaged is an unmanaged image that is not on an atlas.

internal/graphicscommand/shader.go

@@ -31,6 +31,8 @@ type Shader struct {
 	shader graphicsdriver.Shader
 	ir     *shaderir.Program
 	id     int
+
+	// name is used only for logging.
 	name string
 }