MIDIOPENDESC

typedef struct midiopendesc_tag {
    HMIDI hMidi;
    DWORD dwCallback;
    DWORD dwInstance;
    DWORD cIds;
    MIDIOPENSTRMID rgIds[1];
} MIDIOPENDESC;
 

The MIDIOPENDESC structure contains information needed by user-mode MIDI input and MIDI output drivers for sending callback messages to clients. The structure is created by winmm.dll and passed to the user-mode driver along with a MODM_OPEN or MIDM_OPEN message.

Members

hMidi

Specifies the client’s handle to the device, as assigned by winmm.dll. User-mode drivers specify this handle as the hDriver parameter to DriverCallback, when sending a callback message.

dwCallback

Specifies either the address of a callback function, a window handle, an event handle, or a task handle, depending on the flag specified in the dwParam2 parameter of the MODM_OPEN or MIDM_OPEN message.

dwInstance

Contains the dwCallbackInstance argument that the client specified when calling the midiInOpen or midiOutOpen function. This value is returned to the client as the dwInstance parameter to DriverCallback.

cIds

Number of rgIds array elements.

rgIds

Array of stream identifiers, containing one element for each open stream.