Type PressKind
type PressKind = platform.PressKindPressKind is what a press at a window point does in a custom-titlebar window: the application takes it, a control takes it, the platform moves the window at once, or the application takes it and the platform moves the window if the pointer drags. The platform asks the same question of the painted page when a button goes down (see ui.Canvas.MoveRegion).