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