Reserve mixer channel for MIDI playback

Author: benstone

kauai/src/sndsdl.cpp

@@ -13,15 +13,16 @@ ASSERTNAME
 
 #define AssertDoMix(x) AssertDo(x >= 0, Mix_GetError());
 
-typedef int SDLChannelId;
-
 // Maximum number of SDL channels that will be allocated
 const SDLChannelId kSDLChannelIdMac = 32;
 const SDLChannelId kSDLChannelIdInvalid = -1;
 
 const int32_t klwFrequency = 44100;
 const int32_t klwChunkSize = 1024;
 
+// Channel ID reserved for MIDI playback
+const SDLChannelId kSDLChannelIdMidi = 0;
+
 // Number of milliseconds after playing a new sound that pause will be ignored.
 // This is a hack to work around a difference in behaviour in AudioMan.
 // When AudioMan plays a sound it will mix and write a chunk of the sound to the
@@ -492,6 +493,9 @@ PSNQUE SDLSoundDevice::_PsnqueNew(void)
     bool rgfAllocated[kSDLChannelIdMac];
     ClearPb(rgfAllocated, SIZEOF(rgfAllocated));
 
+    // Reserve channel for MIDI playback
+    rgfAllocated[kSDLChannelIdMidi] = fTrue;
+
     for (int32_t iqueue = 0; iqueue < _pglsnqd->IvMac(); iqueue++)
     {
         SNQD snqd;
@@ -505,6 +509,7 @@ PSNQUE SDLSoundDevice::_PsnqueNew(void)
 
         if (ichannel >= 0 && ichannel < CvFromRgv(rgfAllocated))
         {
+            Assert(!rgfAllocated[ichannel], "Mixer channel used by multiple sound queues");
             rgfAllocated[ichannel] = fTrue;
         }
         else

kauai/src/sndsdl.h

@@ -13,6 +13,11 @@
 // Kauai command ID used to indicate that a sound finished playing
 #define cidSDLSoundChannelFinished 110001
 
+typedef int SDLChannelId;
+
+// Channel ID reserved for MIDI playback
+extern const SDLChannelId kSDLChannelIdMidi;
+
 typedef class SDLSoundDevice *PSDLSoundDevice;
 typedef class SDLSoundNotifier *PSDLSoundNotifier;