From 78a0fc6fa593042d22b5613748d84fdd22f7c7b8 Mon Sep 17 00:00:00 2001
From: reuk <reuk@users.noreply.github.com>
Date: Wed, 30 Nov 2022 17:03:47 +0000
Subject: [PATCH] VST3 Client:  Allow setBusArrangements to succeed if called
 during setActive

---
 .../VST3/juce_VST3_Wrapper.cpp                | 35 +++++++++++--------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp b/modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp
index 2aae192862..04fce34f58 100644
--- a/modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp
+++ b/modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp
@@ -2551,26 +2551,31 @@ public:
     //==============================================================================
     tresult PLUGIN_API setActive (TBool state) override
     {
-        active = (state != 0);
+        const auto willBeActive = (state != 0);
 
-        if (! state)
+        active = false;
+        // Some hosts may call setBusArrangements in response to calls made during prepareToPlay
+        // or releaseResources. Specifically, Wavelab 11.1 calls setBusArrangements in the same
+        // call stack when the AudioProcessor calls setLatencySamples inside prepareToPlay.
+        // In order for setBusArrangements to return successfully, the plugin must not be activated
+        // until after prepareToPlay has completely finished.
+        const ScopeGuard scope { [&] { active = willBeActive; } };
+
+        if (willBeActive)
         {
-            getPluginInstance().releaseResources();
+            const auto sampleRate = processSetup.sampleRate > 0.0
+                                  ? processSetup.sampleRate
+                                  : getPluginInstance().getSampleRate();
+
+            const auto bufferSize = processSetup.maxSamplesPerBlock > 0
+                                  ? (int) processSetup.maxSamplesPerBlock
+                                  : getPluginInstance().getBlockSize();
+
+            preparePlugin (sampleRate, bufferSize, CallPrepareToPlay::yes);
         }
         else
         {
-            auto sampleRate = getPluginInstance().getSampleRate();
-            auto bufferSize = getPluginInstance().getBlockSize();
-
-            sampleRate = processSetup.sampleRate > 0.0
-                            ? processSetup.sampleRate
-                            : sampleRate;
-
-            bufferSize = processSetup.maxSamplesPerBlock > 0
-                            ? (int) processSetup.maxSamplesPerBlock
-                            : bufferSize;
-
-            preparePlugin (sampleRate, bufferSize, CallPrepareToPlay::yes);
+            getPluginInstance().releaseResources();
         }
 
         return kResultOk;