Windows, user objects, controls, menus, and Application objects each have a predefined set of events. In most cases, the predefined events are all you need, but there are times when you want to declare your own user event. You can use predefined event IDs to trigger a user event, or you can trigger it exclusively from within your application scripts.
Features that you might want to add to your application by creating user events include keystroke processing, providing multiple ways to perform a task, and communication between a user object and a window.
Suppose that you want to modify the way keystrokes are processed in your application. For example, in a DataWindow control, you want the user to be able to press the Down Arrow and Up Arrow keys to scroll among radio buttons in a DataWindow column. Normally, pressing these keys moves the focus to the next or preceding row.
To do this, you define user events corresponding to Windows events that PowerBuilder does not define.
Suppose that you want to provide several ways to accomplish a certain task within a window. For example, you want the user to be able to update the database by either clicking a button or selecting a menu item. In addition, you want to provide the option of updating the database when the user closes the window.
To do this, you define a user event to update the database.
Suppose that you have placed a custom visual user object in a window and need to communicate between the user object and the window. For information, see “Communicating between a window and a user object”.
