Start a new extension for a new direct_channels state

So existing behavior remains consistent for anything that needs it, and new
behavior is opt-in.

al/source.cpp

@@ -1276,9 +1276,10 @@ bool SetSourceiv(ALsource *Source, ALCcontext *Context, SourceProp prop, const a
 
     case AL_DIRECT_CHANNELS_SOFT:
         CHECKSIZE(values, 1);
-        CHECKVAL(values[0] == AL_FALSE || values[0] == AL_TRUE);
+        CHECKVAL(values[0] == AL_FALSE || values[0] == AL_DROP_UNMATCHED_SOFT /* aka AL_TRUE */
+            || values[0] == AL_REMIX_UNMATCHED_SOFT);
 
-        Source->DirectChannels = values[0] != AL_FALSE;
+        Source->DirectChannels = static_cast<DirectMode>(values[0]);
         return UpdateSourceProps(Source, Context);
 
     case AL_DISTANCE_MODEL:
@@ -1826,7 +1827,7 @@ bool GetSourceiv(ALsource *Source, ALCcontext *Context, SourceProp prop, const a
 
     case AL_DIRECT_CHANNELS_SOFT:
         CHECKSIZE(values, 1);
-        values[0] = Source->DirectChannels;
+        values[0] = static_cast<int>(Source->DirectChannels);
         return true;
 
     case AL_DISTANCE_MODEL:
@@ -3277,7 +3278,7 @@ ALsource::ALsource(ALuint num_sends)
     Looping = AL_FALSE;
     mDistanceModel = DistanceModel::Default;
     mResampler = ResamplerDefault;
-    DirectChannels = AL_FALSE;
+    DirectChannels = DirectMode::Off;
     mSpatialize = SpatializeAuto;
 
     StereoPan[0] = Deg2Rad( 30.0f);

al/source.h

@@ -53,7 +53,7 @@ struct ALsource {
     bool Looping;
     DistanceModel mDistanceModel;
     Resampler mResampler;
-    bool DirectChannels;
+    DirectMode DirectChannels;
     SpatializeMode mSpatialize;
 
     bool DryGainHFAuto;

alc/alu.cpp

@@ -731,7 +731,7 @@ void CalcPanningAndFilters(ALvoice *voice, const ALfloat xpos, const ALfloat ypo
     const auto Frequency = static_cast<ALfloat>(Device->Frequency);
     const ALuint NumSends{Device->NumAuxSends};
 
-    bool DirectChannels{props->DirectChannels != AL_FALSE};
+    DirectMode DirectChannels{props->DirectChannels};
     const ALuint num_channels{voice->mNumChannels};
     const ChanMap *chans{nullptr};
     ALfloat downmix_gain{1.0f};
@@ -740,11 +740,11 @@ void CalcPanningAndFilters(ALvoice *voice, const ALfloat xpos, const ALfloat ypo
     case FmtMono:
         chans = MonoMap;
         /* Mono buffers are never played direct. */
-        DirectChannels = false;
+        DirectChannels = DirectMode::Off;
         break;
 
     case FmtStereo:
-        if(!DirectChannels)
+        if(DirectChannels == DirectMode::Off)
         {
             /* Convert counter-clockwise to clockwise. */
             StereoMap[0].angle = -props->StereoPan[0];
@@ -785,7 +785,7 @@ void CalcPanningAndFilters(ALvoice *voice, const ALfloat xpos, const ALfloat ypo
 
     case FmtBFormat2D:
     case FmtBFormat3D:
-        DirectChannels = false;
+        DirectChannels = DirectMode::Off;
         break;
     }
     ASSUME(num_channels > 0);
@@ -934,7 +934,8 @@ void CalcPanningAndFilters(ALvoice *voice, const ALfloat xpos, const ALfloat ypo
             }
         }
     }
-    else if(DirectChannels && Device->FmtChans != DevFmtMono && Device->FmtChans != DevFmtAmbi3D)
+    else if(DirectChannels != DirectMode::Off && Device->FmtChans != DevFmtMono
+        && Device->FmtChans != DevFmtAmbi3D)
     {
         /* Direct source channels always play local. Skip the virtual channels
          * and write inputs to the matching real outputs.
@@ -946,7 +947,7 @@ void CalcPanningAndFilters(ALvoice *voice, const ALfloat xpos, const ALfloat ypo
             ALuint idx{GetChannelIdxByName(Device->RealOut, chans[c].channel)};
             if(idx != INVALID_CHANNEL_INDEX)
                 voice->mChans[c].mDryParams.Gains.Target[idx] = DryGain.Base;
-            else
+            else if(DirectChannels == DirectMode::RemixMismatch)
             {
                 auto match_channel = [chans,c](const InputRemixMap &map) noexcept -> bool
                 { return chans[c].channel == map.channel; };
@@ -1575,7 +1576,8 @@ void CalcSourceParams(ALvoice *voice, ALCcontext *context, bool force)
         AtomicReplaceHead(context->mFreeVoiceProps, props);
     }
 
-    if(voice->mProps.DirectChannels || voice->mProps.mSpatializeMode == SpatializeOff
+    if(voice->mProps.DirectChannels != DirectMode::Off
+        || voice->mProps.mSpatializeMode == SpatializeOff
         || (voice->mProps.mSpatializeMode == SpatializeAuto && voice->mFmtChannels != FmtMono))
         CalcNonAttnSourceParams(voice, &voice->mProps, context);
     else

alc/inprogext.h

@@ -92,6 +92,12 @@ AL_API void AL_APIENTRY alGetPointervSOFT(ALenum pname, void **values);
 #define AL_N3D_SOFT                              0x0002
 #endif
 
+#ifndef AL_SOFT_direct_channels_remix
+#define AL_SOFT_direct_channels_remix
+#define AL_DROP_UNMATCHED_SOFT                   0x0001
+#define AL_REMIX_UNMATCHED_SOFT                  0x0002
+#endif
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif

alc/voice.h

@@ -24,6 +24,12 @@ enum SpatializeMode {
     SpatializeAuto = AL_AUTO_SOFT
 };
 
+enum class DirectMode : unsigned char {
+    Off = AL_FALSE,
+    DropMismatch = AL_DROP_UNMATCHED_SOFT,
+    RemixMismatch = AL_REMIX_UNMATCHED_SOFT
+};
+
 enum class Resampler {
     Point,
     Linear,
@@ -134,7 +140,7 @@ struct ALvoicePropsBase {
     bool HeadRelative;
     DistanceModel mDistanceModel;
     Resampler mResampler;
-    bool DirectChannels;
+    DirectMode DirectChannels;
     SpatializeMode mSpatializeMode;
 
     bool DryGainHFAuto;