The MOM_OPEN callback message notifies a client that a user-mode driver has finished processing a MODM_OPEN message.
Parameters
dwMsg
MOM_OPEN
dwParam1
NULL
dwParam2
NULL
Comments
A user-mode MIDI output driver sends a MOM_OPEN message to its client, by means of a callback, when the driver finishes processing a MODM_OPEN message. The driver sends the message to the client by calling DriverCallback, passing the specified parameters.
The driver sends the MOM_OPEN message only if the client has specified a notification target with the MODM_OPEN message.
Win32 SDK documentation states that clients receive an MM_MOM_OPEN message if the notification target is a window handle. MOM_OPEN and MM_MOM_OPEN are equivalent.
For more information, see Notifying Clients from Audio Drivers and Transferring MIDI Output Data.