The handler executes the following snippets in a restricted environment: _onclick (self, button, down) : The snippet is executed when button is clicked. self : Secure frame handle to the frame being clicked. button : String - mouse button being clicked ("LeftButton", ...) down : Boolean (1/nil) - If true-equivalent, the click is fired by a down-stroke, i.e. the button being pushed down. If false-equivalent, the click is fired by an up-stroke, i.e. the button being released.