The OnHide event is called when a shown frame is about to be hidden or when a hidden frame is about to become visible on screen. Hiding / Showing a frame that is already hidden / visible does not invoke the OnHide event.
- no known arguments
Have a look at Handling UI Events for an explanation of event handling and some code examples.
Note that "OnHide" also fires whenever any parent frame is hidden, since a parent-frame becoming invisible also makes its entire child-hierarchy invisible, including your frame.