In the Sencha Examples for the Dialog - Auto Size keeps growing when you hit the add button. If you move the dialog close to one of the boundaries of the viewport and click add. The button jumps to the center and stops working - ie. you cannot add or remove anything anymore. Hiding and reshowing the dialog doesn't help, you have to reload the browser for it to work again.

I'm working with a GWT DialogBox and was trying to see how you handle Viewport Boundaries... that's how I came accross this bug.