Dev:UIWindow

UIWindow is a specialized UIView that represents a root node in the view hierarchy. There may be multiple UIWindows.

Non-rectangular windows
By default UIWindows are rectangular. While you may modify the interaction shape of a UIView by overriding -pointInside:withEvent:, this method will be ignored in UIWindow. Instead, there is an undocumented method -acceptsGlobalPoint: that does this job: The global point is always in portrait coordinate.

Getting an array of all windows
You can use the following class method to get an array of all windows.