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modMessage function

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The modMessage function is the entry-point function for musical instrument digital interface (MIDI) output drivers and for internal synthesizer drivers. For more information about audio device messages related to MIDI, see Audio Device Messages for MIDI.

Syntax

DWORD modMessage(
   UINT      uDeviceID,
   UINT      uMsg,
   DWORD_PTR dwUser,
   DWORD_PTR dwParam1,
   DWORD_PTR dwParam2
);

Parameters

  • uDeviceID
    Specifies the ID of the target device. Device IDs are sequential and have an initial value of zero and a final value equal to one less than the number of devices the driver supports.

  • uMsg
    Specifies the message that WINMM sends to the driver in response to a call from the client application.

  • dwUser
    For the MODM_OPEN message, the driver should fill this location with its instance data. For any other messages, the instance data is returned to the driver. Drivers that support multiple clients can use this instance data to track which client is associated with the message.

  • dwParam1
    Specifies a message-dependent parameter.

  • dwParam2
    Specifies a message-dependent parameter. If there are flags that provide additional information to the driver that works with modMessage, WINMM uses this parameter to pass the flags.

Return value

The modMessage function returns MMSYSERR_NOERROR if it can successfully process the message it received from MMSYSTEM. Otherwise, it returns one of the following error messages.

Return code Description
MMSYSERR_ERROR

Unspecified error.
MMSYSERR_BADDEVICEID

The specified device ID is out of range.
MMSYSERR_NOTENABLED

The driver failed to load or initialize.
MMSYSERR_ALLOCATED

The specified device is already allocated.
MMSYSERR_INVALHANDLE

The handle of the specified device is invalid.
MMSYSERR_NODRIVER

No device driver is present.
MMSYSERR_NOMEM

Memory allocation error.
MMSYSERR_NOTSUPPORTED

The function requested by the message is not supported.
MMSYSERR_BADERRNUM

Error value is out of range. See Remarks section for more details.
MMSYSERR_INVALFLAG

An invalid flag was passed to modMessage(by using dwParam2).
MMSYSERR_INVALPARAM

An invalid parameter was passed to modMessage.
MMSYSERR_HANDLEBUSY

The specified handle is being used simultaneously by another thread (for example, a callback thread).
MMSYSERR_INVALIDALIAS

The specified alias was not found.
MMSYSERR_BADDB

Bad registry database.
MMSYSERR_KEYNOTFOUND

The specified registry key was not found.
MMSYSERR_READERROR

Registry read error.
MMSYSERR_WRITEERROR

Registry write error.
MMSYSERR_DELETEERROR

Registry delete error.
MMSYSERR_VALNOTFOUND

The specified registry value was not found.
MMSYSERR_NODRIVERCB

The driver that works with modMessage does not call DriverCallback.
MMSYSERR_MOREDATA

modMessage has more data to return.
MMSYSERR_LASTERROR

Indicates that this is the last error in the range of error values. See the Remarks section for more details.

Remarks

Audio device messages are system-defined constants. So when modMessage receives an audio device message, it uses a switch statement to determine the action to perform, based on the value of the message.

The range of error messages that modMessage can return depends on the message that it was processing when the error occurred. The numerical values of the MMSYSERR_ error messages start with zero (for MMSYSERR_NOERROR) and continue with MMSYSERR_BASE + n, where n is an integer from 1 to 21. The value for MMSYSERR_BASE is a defined constant. For more information about MSYSERR_BASE and the MMSYSERR_ error messages, see Mmsystem.h in the Windows SDK and Mmddk.h in the WDK respectively.

Requirements

Target platform

 Desktop

Version

Available with Windows XP and later Windows operating systems.

Header

 Mmddk.h (include Mmddk.h, Mmsystem.h, or Windows.h)

See also

MODM_OPEN