var rectColor: Color = Color.BLUE;
Stage {
   title: "Application title"
   width: 250
   height: 250
   scene: Scene {
       content: Group{
           content: [
               Rectangle{
                   fill: bind rectColor
                   width: 100
                   height: 100
                   onMousePressed: function( e: MouseEvent ):Void {
                       println("pressed");
                       rectColor = Color.RED
                   }

                   onMouseReleased: function( e: MouseEvent ):Void {
                       println("released");
                       rectColor = Color.BLUE
                   }
               },
               TextBox {
                   translateX: 0
                   translateY: 150
               }
           ]
       }
   }
}

When I run this on both Mac and PC, I see alot of weird delays between when I click on the rectangle and when it responds to it. Sometimes I wont see the color change if i click quickly, sometime when it turns to red it will stay like that for half a second after I've released. Now if I delete the TextBox from the group and run the app, clicking on the rectangle is snappy and responds exactly as I would expect.