WINMM sends the
MODM_GETNUMDEVS message to the modMessage function of a MIDI output driver to request the number of MIDI output devices available.
DWORD modMessage( UINT uDeviceID, UINT uMsg, DWORD_PTR dwUser, DWORD_PTR dwParam1, DWORD_PTR dwParam2 );
Specifies the ID of the target device. Device IDs are sequential and have an initial value of zero and a final value that is equal to one less than the number of devices that the driver supports.
WINMM sets this parameter to MODM_GETNUMDEVS when it calls modMessage to process this message.
Use this parameter to return instance data to the driver. Drivers that support multiple clients can use this instance data to keep track of the client that is associated with the message.
The modMessage function returns the number of MIDI output devices that the driver supports.
Drivers can be structured in several ways. The simplest and most common drivers use one physical device to support one logical device. Drivers can also support multiple logical devices by using a single physical device. For example, a driver can use a single digital signal processor (DSP) to support two different types of internal synthesizers. Such a driver would return a value of "2" in response to the
|Available in Windows XP and later Windows operating systems.|
Build date: 11/16/2013