UIHANDLER OnDragStart

Fires when starting to drag a Frame. (self, button)

Arguments

 * self : - The widget on which the mouse button was pressed.
 * button : - "LeftButton", "RightButton", "MiddleButton", "Button4", "Button5", ..., "ButtonN"

Details

 * The mouse button must be pressed down within the frame and moved more than several (~10) pixels in any direction without being released.
 * Preceeded by
 * Replaces and  with.