imaqSetEventCallback

Usage

int imaqSetEventCallback(EventCallback callback, int synchronous);

Purpose

Sets a callback function that NI Vision calls when an event occurs in a window. When a user generates an event, NI Vision calls the callback function using the following parameters: event, window number, tool, and location of the event. For a full description of these parameters, refer to imaqGetLastEvent().

Parameters

Name	Type	Description
callback	EventCallback	The function to call. Set this parameter to NULL if you want to disable event processing using a callback. If you disable callbacks, you can process events using imaqGetLastEvent().
synchronous	int	Set this parameter to TRUE to call the callback function in the thread that calls imaqSetEventCallback(). Set this parameter to FALSE to call the callback function asynchronously in a separate thread. To process callbacks synchronously, your application must have a message pump. In LabWindows/CVI, calling RunUserInterface() starts a message pump. The function ignores this parameter if callback is NULL.

Return Value

Type	Description
int	On success, this function returns a non-zero value. On failure, this function returns 0. To get extended error information, call imaqGetLastError().

Parameter Discussion

callback—callback should have the following prototype: void IMAQ_CALLBACK MyCallback(WindowEventType, int windowNumber, Tool tool, Rect rect);