wmme: document default device selection algorithm

diff --git a/src/hostapi/wmme/pa_win_wmme.c b/src/hostapi/wmme/pa_win_wmme.c
index 5a3458833d468b201caebc92d13428c1272c08f2..5f373f549fcaa17adf33ace348ae8eba590a320e 100644 (file)
--- a/src/hostapi/wmme/pa_win_wmme.c
+++ b/src/hostapi/wmme/pa_win_wmme.c
@@ -1018,6 +1018,16 @@ PaError PaWinMme_Initialize( PaUtilHostApiRepresentation **hostApi, PaHostApiInd
     winMmeHostApi->inputDeviceCount = 0;
     winMmeHostApi->outputDeviceCount = 0;
 
+    /* Default device determination:
+       Here we query for the system preferred input and output devices using
+       DRVM_MAPPER_PREFERRED_GET; on error fall back to WAVE_MAPPER. Preferred
+       devices are stored in wave{In, Out}PreferredDevice.
+
+       When enumerating devices, set PA default devices to the MME devices
+       with ids matching wave{In, Out}PreferredDevice. If such devices are not
+       encountered during enumeration, the first device enumerated for each of
+       {input, output} will be selected as the PA default device.
+    */
     preferredDeviceStatusFlags = 0;
     waveInPreferredDevice = WAVE_MAPPER;
     if( waveInMessage( (HWAVEIN)WAVE_MAPPER, DRVM_MAPPER_PREFERRED_GET, (DWORD_PTR)&waveInPreferredDevice, (DWORD_PTR)&preferredDeviceStatusFlags ) != MMSYSERR_NOERROR )