Button takes advantage of the rendering hints

elements/core/core.go

@@ -112,10 +112,13 @@ func (control CoreControl) HasImage () (has bool) {
 
 // DamageRegion pushes the selected region of pixels to the parent element. This
 // does not need to be called when responding to a resize event.
-func (control CoreControl) DamageRegion (bounds image.Rectangle) {
+func (control CoreControl) DamageRegion (regions ...image.Rectangle) {
 	if control.core.canvas == nil { return }
 	if control.core.onDamage != nil {
-		control.core.onDamage(canvas.Cut(control.core.canvas, bounds))
+		for _, region := range regions {
+			control.core.onDamage (
+				canvas.Cut(control.core.canvas, region))
+		}
 	}
 }