GUIBaseContext :: doAfterOpen - Control open handler

The handler handles the GEV_Opened GUI event. The event is fired after opening a control. When the event is fired, the control and its subordinated elements are created, but the data source is usually not yet opened. The event is typically used to enable/disable controls or buttons or to open application defined data sources.

The handler should return one of the following return codes:

• -1 (not handled) - the event handler will be removed from the handler list and is not called anymore.
• 1 (error) - Returning an error has no effect for post-events.
• 0 (ok) - Event handler terminated successfully.