The MIM_MOREDATA callback message notifies a client that a user-mode driver has received a MIDI short message, and the client is not processing MIM_DATA messages fast enough to keep up with the driver.
Parameters
dwMsg
MIM_MOREDATA
dwParam1
MIDI short message contents (one to three bytes).
dwParam2
Time stamp. Number of milliseconds since MIDM_START was received.
Comments
A user-mode MIDI input driver sends a MIM_MOREDATA message to its client, by means of a callback, when the driver has received a MIDI short message and the client is not processing MIM_DATA messages fast enough to keep up with the driver. The driver sends the message to the client by calling DriverCallback, passing the specified parameters.
The driver sends the MIM_MOREDATA message only if the client has previously specified a notification target with a MIDM_OPEN message, and only if the MIDI_IO_STATUS flag was included with the MIDM_OPEN message.
Currently, mmdrv.dll and drvlib.lib do not send MIM_MOREDATA messages.
If the driver detects that the message is invalid, it should send MIM_ERROR instead of MIM_MOREDATA.
Win32 SDK documentation states that clients receive a MM_MIM_MOREDATA message if the notification target is a window handle. MIM_MOREDATA and MM_MIM_MOREDATA are equivalent.
For additional information, see Notifying Clients from Audio Drivers and Transferring MIDI Input Data.