GUIBaseContext :: doBeforeInsertData - Pre-event handler for Insert-data events

The pre-event handler for a DEV_Insert event is called from within an AppendEntry or InsertEntry action after initializing the new instance. The handler allows modifying the key or data for the new instance to be created. In order to update instance data, the new instance can be provided by calling newInstance().

In order to refuse creating a new instance the handler may return 1.

The handler should return one of the following values:

• -1 (not handled) - the event handler will be removed from the handler list and is not called anymore.
• 1 (refuse) - Requested action will not be executed.
• 0 (ok) - Action is permitted to be executed.