From bad650042437dbec10f632f081f137a10c64bd3f Mon Sep 17 00:00:00 2001
From: ed <eddavies95@gmail.com>
Date: Mon, 6 Jan 2020 14:20:57 +0000
Subject: [PATCH] Added activeEditorLock to AudioProcessor to replace
 callbackLock when accessing its activeEditor member to prevent priority
 inversion issues

---
 .../processors/juce_AudioProcessor.cpp        | 20 ++++++++++++++-----
 .../processors/juce_AudioProcessor.h          | 11 ++++++----
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/modules/juce_audio_processors/processors/juce_AudioProcessor.cpp b/modules/juce_audio_processors/processors/juce_AudioProcessor.cpp
index 9f09963478..bd40623c53 100644
--- a/modules/juce_audio_processors/processors/juce_AudioProcessor.cpp
+++ b/modules/juce_audio_processors/processors/juce_AudioProcessor.cpp
@@ -52,8 +52,12 @@ AudioProcessor::AudioProcessor (const BusesProperties& ioConfig)
 
 AudioProcessor::~AudioProcessor()
 {
-    // ooh, nasty - the editor should have been deleted before its AudioProcessor.
-    jassert (activeEditor == nullptr);
+    {
+        const ScopedLock sl (activeEditorLock);
+
+        // ooh, nasty - the editor should have been deleted before its AudioProcessor.
+        jassert (activeEditor == nullptr);
+    }
 
    #if JUCE_DEBUG && ! JUCE_DISABLE_AUDIOPROCESSOR_BEGIN_END_GESTURE_CHECKING
     // This will fail if you've called beginParameterChangeGesture() for one
@@ -803,14 +807,22 @@ void AudioProcessor::audioIOChanged (bool busNumberChanged, bool channelNumChang
 //==============================================================================
 void AudioProcessor::editorBeingDeleted (AudioProcessorEditor* const editor) noexcept
 {
-    const ScopedLock sl (callbackLock);
+    const ScopedLock sl (activeEditorLock);
 
     if (activeEditor == editor)
         activeEditor = nullptr;
 }
 
+AudioProcessorEditor* AudioProcessor::getActiveEditor() const noexcept
+{
+    const ScopedLock sl (activeEditorLock);
+    return activeEditor;
+}
+
 AudioProcessorEditor* AudioProcessor::createEditorIfNeeded()
 {
+    const ScopedLock sl (activeEditorLock);
+
     if (activeEditor != nullptr)
         return activeEditor;
 
@@ -820,8 +832,6 @@ AudioProcessorEditor* AudioProcessor::createEditorIfNeeded()
     {
         // you must give your editor comp a size before returning it..
         jassert (ed->getWidth() > 0 && ed->getHeight() > 0);
-
-        const ScopedLock sl (callbackLock);
         activeEditor = ed;
     }
 
diff --git a/modules/juce_audio_processors/processors/juce_AudioProcessor.h b/modules/juce_audio_processors/processors/juce_AudioProcessor.h
index a91f1ed2ba..ba11e3131d 100644
--- a/modules/juce_audio_processors/processors/juce_AudioProcessor.h
+++ b/modules/juce_audio_processors/processors/juce_AudioProcessor.h
@@ -964,10 +964,13 @@ public:
     virtual bool hasEditor() const = 0;
 
     //==============================================================================
-    /** Returns the active editor, if there is one.
-        Bear in mind this can return nullptr, even if an editor has previously been opened.
+    /** Returns the active editor, if there is one. Bear in mind this can return nullptr
+        even if an editor has previously been opened.
+
+        Note that you should only call this method from the message thread as the active
+        editor may be deleted by the message thread, causing a dangling pointer.
     */
-    AudioProcessorEditor* getActiveEditor() const noexcept             { return activeEditor; }
+    AudioProcessorEditor* getActiveEditor() const noexcept;
 
     /** Returns the active editor, or if there isn't one, it will create one.
         This may call createEditor() internally to create the component.
@@ -1465,7 +1468,7 @@ private:
     int blockSize = 0, latencySamples = 0;
     bool suspended = false, nonRealtime = false;
     ProcessingPrecision processingPrecision = singlePrecision;
-    CriticalSection callbackLock, listenerLock;
+    CriticalSection callbackLock, listenerLock, activeEditorLock;
 
     friend class Bus;
     mutable OwnedArray<Bus> inputBuses, outputBuses;