Sets func to be called when a popup is about to be shown.
func should use one of
to set a popup for this. If func is non-null,
this will always be sensitive.
Using this function will not reset the menu widget attached to this. Instead, this can be done manually
in func.
| this |
a `GtkMenuButton` |
| func |
function to call when a popup is about to be shown, but none has been provided via other means, or null to reset to default behavior. |
| destroy_notify |
destroy notify for |
| user_data |
user data to pass to |