MXDM_GETLINEINFO
Sent to an audio mixer device driver to get information on the specified line. This message is normally sent to an audio mixer driver in response to a mixerGetLineInfo call.
- The return value is an error code, or zero (MMSYSERR_NOERROR) if the operation is successful. Possible error codes are:
| MMSYSERR_NOTENABLED |
The driver failed to load or initialize. |
| MIXERR_INVALLINE |
The audio mixer device line reference is invalid. |
- dwParam1
- Specifies a pointer to a MIXERLINE structure that is to receive the line information being requested.
- dwParam2
- Specifies flags for getting the line information. This argument is identical to the fdwInfo argument passed to the mixerGetLineInfo function. Refer to the description for mixerGetLineInfo for specific flag information.
An audio mixer driver must support this message. The Mixer Manager will validate the following parameters for the MXDM_GETLINEINFO message before calling the driver. Your driver does not need to check for the following conditions:
- dwParam1 will contain a valid pointer to a MIXERLINE structure. This structure will be at least large enough to hold the base MIXERLINE structure members. This buffer has also been validated to insure it is big enough to hold at least cbStruct bytes of information.
- dwParam2 will be a valid combination of flags.
A mixer device driver must validate the dwDestination, dwSource and dwLineID members of the MIXERLINE structure when they apply to the query request. The driver must also verify that the dwComponentType and Target structure members are valid for the MIXER_GETLINEINFOF_COMPONENTTYPE and MIXER_GETLINEINFOF_TARGETTYPE queries.
An application can generate the following queries for retrieving mixer line information. A driver must use the bitwise AND operator with dwParam2 and the MIXER_GETLINEINFOF_QUERYMASK constant to obtain the query type.
- If the result matches the MIXER_GETLINEINFOF_DESTINATION constant, the query requests information about the destination line specified by MIXERLINE.dwDestination.
- If the result matches the MIXER_GETLINEINFOF_SOURCE constant, the query requests information about the source line (specified by MIXERLINE.dwSource) associated with the destination line specified by MIXERLINE.dwDestination.
- If the result matches the MIXER_GETLINEINFOF_LINEID constant, the query requests information about the line specified by MIXERLINE.dwLineID.
- If the result matches the MIXER_GETLINEINFOF_COMPONENTTYPE constant, the query requests information about the first component of the specified type (MIXERLINE.dwComponentType) on the specifie line.
- If the result matches the MIXER_GETLINEINFOF_TARGETTYPE constant, the query requests information for a line that matches the specified audio line type in MIXERLINE.Target.dwType. For example, if the value of MIXERLINE.Target.dwType is wPid, the query would search for a wave input audio line.
All mixer drivers must support these queries. If a query other than those previously mentioned is sent, the mixer driver must return MMSYSERR_NOTSUPPORTED.