AU Host: Refactor PositionInfo usage

This avoids repeating the 'fallback' values in the case that the
AudioPlayHead or PositionInfo is not available.

As a side-effect of this change, when an AudioPlayHead is available but
does not supply a valid BPM value, a fallback of 120 will be used,
instead of 0. This fixes an issue where the Microtonic sequencer failed
to play in the AudioPluginHost.

modules/juce_audio_processors/format_types/juce_AudioUnitPluginFormat.mm

@@ -2293,43 +2293,43 @@ private:
         if (p != nullptr) *p = value;
     }
 
-    OSStatus getBeatAndTempo (Float64* outCurrentBeat, Float64* outCurrentTempo) const
+    /*  If the AudioPlayHead is available, and has valid PositionInfo, this will return the result
+        of calling the specified getter on that PositionInfo. Otherwise, this will return a
+        default-constructed instance of the same type.
+
+        For getters that return an Optional, this function will return a nullopt if the playhead or
+        position info is invalid.
+
+        For getters that return a bool, this function will return false if the playhead or position
+        info is invalid.
+    */
+    template <typename Result>
+    Result getFromPlayHead (Result (AudioPlayHead::PositionInfo::* member)() const) const
     {
         if (auto* ph = getPlayHead())
-        {
             if (const auto pos = ph->getPosition())
-            {
-                setIfNotNull (outCurrentBeat, pos->getPpqPosition().orFallback (0.0));
-                setIfNotNull (outCurrentTempo, pos->getBpm().orFallback (0.0));
-                return noErr;
-            }
-        }
+                return ((*pos).*member)();
 
-        setIfNotNull (outCurrentBeat, 0);
-        setIfNotNull (outCurrentTempo, 120.0);
+        return {};
+    }
+
+    OSStatus getBeatAndTempo (Float64* outCurrentBeat, Float64* outCurrentTempo) const
+    {
+        setIfNotNull (outCurrentBeat,  getFromPlayHead (&AudioPlayHead::PositionInfo::getPpqPosition).orFallback (0));
+        setIfNotNull (outCurrentTempo, getFromPlayHead (&AudioPlayHead::PositionInfo::getBpm).orFallback (120.0));
         return noErr;
     }
 
     OSStatus getMusicalTimeLocation (UInt32* outDeltaSampleOffsetToNextBeat, Float32* outTimeSig_Numerator,
                                      UInt32* outTimeSig_Denominator, Float64* outCurrentMeasureDownBeat) const
     {
-        if (auto* ph = getPlayHead())
-        {
-            if (const auto pos = ph->getPosition())
-            {
-                const auto signature = pos->getTimeSignature().orFallback (AudioPlayHead::TimeSignature{});
-                setIfNotNull (outDeltaSampleOffsetToNextBeat, (UInt32) 0); //xxx
-                setIfNotNull (outTimeSig_Numerator,   (UInt32) signature.numerator);
-                setIfNotNull (outTimeSig_Denominator, (UInt32) signature.denominator);
-                setIfNotNull (outCurrentMeasureDownBeat, pos->getPpqPositionOfLastBarStart().orFallback (0.0)); //xxx wrong
-                return noErr;
-            }
-        }
+        setIfNotNull (outDeltaSampleOffsetToNextBeat, (UInt32) 0); //xxx
+        setIfNotNull (outCurrentMeasureDownBeat, getFromPlayHead (&AudioPlayHead::PositionInfo::getPpqPositionOfLastBarStart).orFallback (0.0));
+
+        const auto signature = getFromPlayHead (&AudioPlayHead::PositionInfo::getTimeSignature).orFallback (AudioPlayHead::TimeSignature{});
+        setIfNotNull (outTimeSig_Numerator,   (UInt32) signature.numerator);
+        setIfNotNull (outTimeSig_Denominator, (UInt32) signature.denominator);
 
-        setIfNotNull (outDeltaSampleOffsetToNextBeat, (UInt32) 0);
-        setIfNotNull (outTimeSig_Numerator, (UInt32) 4);
-        setIfNotNull (outTimeSig_Denominator, (UInt32) 4);
-        setIfNotNull (outCurrentMeasureDownBeat, 0);
         return noErr;
     }
 
@@ -2337,34 +2337,16 @@ private:
                                 Float64* outCurrentSampleInTimeLine, Boolean* outIsCycling,
                                 Float64* outCycleStartBeat, Float64* outCycleEndBeat)
     {
-        if (auto* ph = getPlayHead())
-        {
-            AudioPlayHead::CurrentPositionInfo result;
+        const auto nowPlaying = getFromPlayHead (&AudioPlayHead::PositionInfo::getIsPlaying);
+        setIfNotNull (outIsPlaying, nowPlaying);
+        setIfNotNull (outTransportStateChanged, std::exchange (wasPlaying, nowPlaying) != nowPlaying);
+        setIfNotNull (outCurrentSampleInTimeLine, getFromPlayHead (&AudioPlayHead::PositionInfo::getTimeInSamples).orFallback (0));
+        setIfNotNull (outIsCycling, getFromPlayHead (&AudioPlayHead::PositionInfo::getIsLooping));
 
-            if (ph->getCurrentPosition (result))
-            {
-                setIfNotNull (outIsPlaying, result.isPlaying);
-
-                if (outTransportStateChanged != nullptr)
-                {
-                    *outTransportStateChanged = result.isPlaying != wasPlaying;
-                    wasPlaying = result.isPlaying;
-                }
-
-                setIfNotNull (outCurrentSampleInTimeLine, result.timeInSamples);
-                setIfNotNull (outIsCycling, result.isLooping);
-                setIfNotNull (outCycleStartBeat, result.ppqLoopStart);
-                setIfNotNull (outCycleEndBeat, result.ppqLoopEnd);
-                return noErr;
-            }
-        }
+        const auto loopPoints = getFromPlayHead (&AudioPlayHead::PositionInfo::getLoopPoints).orFallback (AudioPlayHead::LoopPoints{});
+        setIfNotNull (outCycleStartBeat, loopPoints.ppqStart);
+        setIfNotNull (outCycleEndBeat, loopPoints.ppqEnd);
 
-        setIfNotNull (outIsPlaying, false);
-        setIfNotNull (outTransportStateChanged, false);
-        setIfNotNull (outCurrentSampleInTimeLine, 0);
-        setIfNotNull (outIsCycling, false);
-        setIfNotNull (outCycleStartBeat, 0.0);
-        setIfNotNull (outCycleEndBeat, 0.0);
         return noErr;
     }