From 3bc38d1e3be3d830f7b00c50c0d4de9908a5ee8e Mon Sep 17 00:00:00 2001
From: jules <jules@juce.com>
Date: Thu, 7 Jan 2016 09:41:36 +0000
Subject: [PATCH] AudioUnit hosting: added code to handle plugin latency
 changes

---
 .../juce_AudioUnitPluginFormat.mm             | 47 +++++++++++--------
 1 file changed, 28 insertions(+), 19 deletions(-)

diff --git a/modules/juce_audio_processors/format_types/juce_AudioUnitPluginFormat.mm b/modules/juce_audio_processors/format_types/juce_AudioUnitPluginFormat.mm
index d42534cb66..24063c6a5a 100644
--- a/modules/juce_audio_processors/format_types/juce_AudioUnitPluginFormat.mm
+++ b/modules/juce_audio_processors/format_types/juce_AudioUnitPluginFormat.mm
@@ -445,12 +445,7 @@ public:
                                   (int) (numOutputBusChannels * numOutputBusses),
                                   (double) newSampleRate, estimatedSamplesPerBlock);
 
-            Float64 latencySecs = 0.0;
-            UInt32 latencySize = sizeof (latencySecs);
-            AudioUnitGetProperty (audioUnit, kAudioUnitProperty_Latency, kAudioUnitScope_Global,
-                                  0, &latencySecs, &latencySize);
-
-            setLatencySamples (roundToInt (latencySecs * newSampleRate));
+            updateLatency();
 
             {
                 AudioStreamBasicDescription stream;
@@ -889,6 +884,16 @@ public:
         }
     }
 
+    void updateLatency()
+    {
+        Float64 latencySecs = 0.0;
+        UInt32 latencySize = sizeof (latencySecs);
+        AudioUnitGetProperty (audioUnit, kAudioUnitProperty_Latency, kAudioUnitScope_Global,
+                              0, &latencySecs, &latencySize);
+
+        setLatencySamples (roundToInt (latencySecs * getSampleRate()));
+    }
+
     void handleIncomingMidiMessage (void*, const MidiMessage& message)
     {
         const ScopedLock sl (midiInLock);
@@ -993,22 +998,24 @@ private:
                 AUEventListenerAddEventType (eventListenerRef, nullptr, &event);
             }
 
-            // Add a listener for program changes
-            AudioUnitEvent event;
-            event.mArgument.mProperty.mAudioUnit = audioUnit;
-            event.mArgument.mProperty.mPropertyID = kAudioUnitProperty_PresentPreset;
-            event.mArgument.mProperty.mScope = kAudioUnitScope_Global;
-            event.mArgument.mProperty.mElement = 0;
-
-            event.mEventType = kAudioUnitEvent_PropertyChange;
-            AUEventListenerAddEventType (eventListenerRef, nullptr, &event);
-
-            // Add a listener for parameter list changes
-            event.mArgument.mProperty.mPropertyID = kAudioUnitProperty_ParameterList;
-            AUEventListenerAddEventType (eventListenerRef, nullptr, &event);
+            addPropertyChangeListener (kAudioUnitProperty_PresentPreset);
+            addPropertyChangeListener (kAudioUnitProperty_ParameterList);
+            addPropertyChangeListener (kAudioUnitProperty_Latency);
         }
     }
 
+    void addPropertyChangeListener (AudioUnitPropertyID type) const
+    {
+        AudioUnitEvent event;
+        event.mEventType = kAudioUnitEvent_PropertyChange;
+        event.mArgument.mProperty.mPropertyID = type;
+        event.mArgument.mProperty.mAudioUnit = audioUnit;
+        event.mArgument.mProperty.mPropertyID = kAudioUnitProperty_PresentPreset;
+        event.mArgument.mProperty.mScope = kAudioUnitScope_Global;
+        event.mArgument.mProperty.mElement = 0;
+        AUEventListenerAddEventType (eventListenerRef, nullptr, &event);
+    }
+
     void eventCallback (const AudioUnitEvent& event, AudioUnitParameterValue newValue)
     {
         switch (event.mEventType)
@@ -1040,6 +1047,8 @@ private:
                     updateHostDisplay();
                 else if (event.mArgument.mProperty.mPropertyID == kAudioUnitProperty_PresentPreset)
                     sendAllParametersChangedEvents();
+                else if (event.mArgument.mProperty.mPropertyID == kAudioUnitProperty_Latency)
+                    updateLatency();
 
                 break;
         }