Patch for te::ExternalPlugin for async instantiation of AUv3 plugins on iOS

auv3-ios-tracktion-develop.patch

diff --git a/modules/tracktion_engine/plugins/external/tracktion_ExternalPlugin.cpp b/modules/tracktion_engine/plugins/external/tracktion_ExternalPlugin.cpp
index 46d380c2b3..b490fabdb1 100644
--- a/modules/tracktion_engine/plugins/external/tracktion_ExternalPlugin.cpp
+++ b/modules/tracktion_engine/plugins/external/tracktion_ExternalPlugin.cpp
@@ -823,19 +823,40 @@ void ExternalPlugin::doFullInitialisation()
         identiferString = createIdentifierString (desc);
         updateDebugName();
 
-        if (processing && pluginInstance == nullptr && engine.getEngineBehaviour().shouldLoadPlugin (*this))
+      if ((processing && pluginInstance == nullptr && engine.getEngineBehaviour().shouldLoadPlugin (*this)) ||
+          waitingForInstance)
         {
             if (isDisabled())
                 return;
 
             CRASH_TRACER_PLUGIN (getDebugName());
             loadError = {};
-
+          
+            #if JUCE_IOS
+            // AUv3 requires async instantiation on iOS
+            if (isAU())
+            {
+              if (!waitingForInstance)
+              {
+                waitingForInstance = true;
+                createPluginInstanceAsync (*foundDesc);
+                return;
+              }
+              if (!asyncError.isEmpty())
+              {
+                loadError = asyncError;
+                asyncError = {};
+              }
+              jassert (pluginInstance);
+              waitingForInstance = false;
+            }
+            #else
             callBlocking ([this, &foundDesc]
             {
                 CRASH_TRACER_PLUGIN (getDebugName());
                 loadError = createPluginInstance (*foundDesc);
             });
+            #endif
 
             if (pluginInstance != nullptr)
             {
@@ -1301,7 +1322,7 @@ void ExternalPlugin::applyToBuffer (const PluginRenderContext& fc)
 {
     const bool processedBypass = fc.allowBypassedProcessing && ! isEnabled();
 
-    if (pluginInstance != nullptr && (processedBypass || isEnabled()))
+    if (pluginInstance != nullptr && (processedBypass || isEnabled()) && !waitingForInstance)
     {
         CRASH_TRACER_PLUGIN (getDebugName());
         const juce::ScopedLock sl (lock);
@@ -1715,6 +1736,31 @@ juce::String ExternalPlugin::createPluginInstance (const juce::PluginDescription
     return error;
 }
 
+void ExternalPlugin::createPluginInstanceAsync (const juce::PluginDescription& description)
+{
+  jassert (! pluginInstance); // This should have already been deleted!
+
+  auto& dm = engine.getDeviceManager();
+
+  fullyInitialised = false;
+
+  juce::String error;
+  engine.getPluginManager().pluginFormatManager
+  .createPluginInstanceAsync (description, dm.getSampleRate(), dm.getBlockSize(),
+                              [&](auto _instance, const auto& err) -> void {
+    pluginInstance = std::move(_instance);
+    asyncError = err;
+
+    if (pluginInstance != nullptr)
+    {
+      pluginInstance->enableAllBuses();
+      processorChangedManager = std::make_unique<ProcessorChangedManager> (*this);
+      initialiseFully();
+      initialise({ 0_tp, sampleRate, blockSizeSamples });
+    }
+  });
+}
+
 void ExternalPlugin::deletePluginInstance()
 {
     processorChangedManager.reset();
diff --git a/modules/tracktion_engine/plugins/external/tracktion_ExternalPlugin.h b/modules/tracktion_engine/plugins/external/tracktion_ExternalPlugin.h
index 450473f5d0..5b050a16d8 100644
--- a/modules/tracktion_engine/plugins/external/tracktion_ExternalPlugin.h
+++ b/modules/tracktion_engine/plugins/external/tracktion_ExternalPlugin.h
@@ -150,6 +150,8 @@ private:
     std::unique_ptr<PluginPlayHead> playhead;
 
     bool fullyInitialised = false, supportsMPE = false, isFlushingLayoutToState = false;
+    bool waitingForInstance = false;
+    juce::String asyncError;
 
     struct MPEChannelRemapper;
     std::unique_ptr<MPEChannelRemapper> mpeRemapper;
@@ -160,6 +162,7 @@ private:
 
     //==============================================================================
     juce::String createPluginInstance (const juce::PluginDescription&);
+    void createPluginInstanceAsync (const juce::PluginDescription&);
     void deletePluginInstance();
 
     //==============================================================================