The ACMDM_DRIVER_ABOUT message requests an ACM driver to display its About dialog box.
Parameters
dwDriverID
Driver instance identifier. This is the value returned by the driver in response to the DRV_OPEN message.
hDriver
Driver handle.
uMsg
ACMDM_DRIVER_ABOUT
lParam1
Contains a validated window handle, which the driver should use to specify the parent window for the About dialog box. The value can also be -1L (See the Comments section below).
lParam2
Not used.
Return Value
The driver should return MMSYSERR_NOERROR if the operation succeeds. Otherwise it should return one of the MMSYSERR error codes defined in mmsystem.h, or one of the ACMERR error codes defined in msacm.h. If the driver does not provide an about box, it should return MMSYSERR_NOTSUPPORTED.
Comments
A client sends the ACMDM_DRIVER_ABOUT message by calling the driver’s DriverProc entry point, passing the specified parameters.
Typically, this message is sent by the Control Panel’s Multimedia applet.
An ACM driver does not have to provide an About dialog box. If it does not, it should always return MMSYSERR_NOTSUPPORTED in response to this message. The ACM provides a default About dialog box, which is displayed if the driver does not provide one.
If the driver does provide an About box, it should display it when it receives this message.
If lParam1 is -1L, the driver should not display its About dialog box. It should just return MMSYSERR_NOERROR if it provides an About box, and MMSYSERR_NOTSUPPORTED if it does not.
For more information about custom About boxes, see Providing a Custom About Box.