DTWAIN_SetCallback64
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The DTWAIN_SetCallback64 allows an application to use a callback function for DTWAIN notifications.
DTWAIN_CALLBACK_PROC64 DTWAIN_SetCallback64 (
Parameters lpProc A pointer to a function that will be called whenever a DTWAIN notification is sent, or NULL (0) to turn off the callback mechanism.
UserData Optional 64-bit user-defined data that will be passed when Callback function is invoked. If the UserData requires a 32-bit type, use DTWAIN_SetCallback.
Return Values If a callback function was previously set, this function returns the last callback function. Otherwise a NULL is returned.
Comments DTWAIN_SetCallback64 operates the same way as DTWAIN_SetCallback. The only difference is that the UserData is specified as a 64-bit type instead of a 32-bit type, and that the callback function, lProc, must have the following prototype:
LRESULT CALLBACK DTWAINCallbackProc(WPARAM wParam, LPARAM lParam, DTWAIN_LONG64 UserData);
If your application has set callback functions using both DTWAIN_SetCallback and DTWAIN_SetCallback64, the callback function associated with DTWAIN_SetCallback is always called prior to calling the callback function associated with DTWAIN_SetCallback64. Therefore, if you have both callbacks invoked, the callback associated with DTWAIN_SetCallback64 must return the proper LRESULT value, else the program will invoke erratic behavior.
For Windows C/C++ programmers: A DTWAIN_LONG64 type is equivalent to a 64-bit integer type. Most compilers also recognize __int64 or equivalent integer types as a 64-bit type, and therefore can be used as the UserData parameter.
See DTWAIN Notifications Using a Callback Function for more details.
TWAIN State Transitions None.
Prerequisite Function Call(s)
See Also |