Event processing in visual extensions

A visual extension can have a window procedure that can process any Windows message or user-defined message. The PBVM passes all such messages to the visual extension, which can intercept messages and either process or ignore them.

WindowProc is an application-defined callback function that processes messages sent to a window. In the example in this section, a WM_PAINT message is sent to the extension when an action in the PowerBuilder application causes the window to be redrawn. When the extension receives the message, it repaints an area in the window using the current values for text and color set by the user of the application.

The following example also captures mouse clicks and double clicks, and triggers the Onclick and Ondoubleclick event scripts in the PowerBuilder application. You can use two different syntaxes for describing events:

event returnType eventName(args_desc) newline

event eventName pbevent_token newline