From 1059f7b0225dec924ef18fd5fbef57ae7a00c89e Mon Sep 17 00:00:00 2001
From: ed <eddavies95@gmail.com>
Date: Wed, 1 Dec 2021 12:46:06 +0000
Subject: [PATCH] DropShadower:  Check for deletion after calling
 isWindowOnCurrentVirtualDesktop()

---
 modules/juce_gui_basics/misc/juce_DropShadower.cpp | 7 +++++++
 modules/juce_gui_basics/misc/juce_DropShadower.h   | 1 +
 2 files changed, 8 insertions(+)

diff --git a/modules/juce_gui_basics/misc/juce_DropShadower.cpp b/modules/juce_gui_basics/misc/juce_DropShadower.cpp
index c98c4b7939..cbd05cc7f0 100644
--- a/modules/juce_gui_basics/misc/juce_DropShadower.cpp
+++ b/modules/juce_gui_basics/misc/juce_DropShadower.cpp
@@ -157,9 +157,16 @@ private:
 
     void timerCallback() override
     {
+        WeakReference<DropShadower> deletionChecker { static_cast<DropShadower*> (listener) };
+
         const auto wasOnVirtualDesktop = std::exchange (isOnVirtualDesktop,
                                                         isWindowOnCurrentVirtualDesktop (root->getWindowHandle()));
 
+        // on Windows, isWindowOnCurrentVirtualDesktop() may cause synchronous messages to be dispatched
+        // to the HWND so we need to check if the shadower is still valid after calling
+        if (deletionChecker == nullptr)
+            return;
+
         if (isOnVirtualDesktop != wasOnVirtualDesktop)
             listener->componentVisibilityChanged (*root);
     }
diff --git a/modules/juce_gui_basics/misc/juce_DropShadower.h b/modules/juce_gui_basics/misc/juce_DropShadower.h
index a142bd3bcd..38babb5a30 100644
--- a/modules/juce_gui_basics/misc/juce_DropShadower.h
+++ b/modules/juce_gui_basics/misc/juce_DropShadower.h
@@ -79,6 +79,7 @@ private:
     std::unique_ptr<ParentVisibilityChangedListener> visibilityChangedListener;
 
     JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (DropShadower)
+    JUCE_DECLARE_WEAK_REFERENCEABLE (DropShadower)
 };
 
 } // namespace juce