From acddcd550d6dd88915c23a63f0b843bd820860d7 Mon Sep 17 00:00:00 2001
From: reuk <reuk@users.noreply.github.com>
Date: Thu, 14 Oct 2021 19:57:44 +0100
Subject: [PATCH] DropShadower:  Detect when window is no longer being
 displayed on the current desktop and hide shadows

---
 modules/juce_gui_basics/juce_gui_basics.cpp   | 53 ++++++++++++++++++-
 .../misc/juce_DropShadower.cpp                | 25 +++++----
 2 files changed, 67 insertions(+), 11 deletions(-)

diff --git a/modules/juce_gui_basics/juce_gui_basics.cpp b/modules/juce_gui_basics/juce_gui_basics.cpp
index 521949f7bb..d150073588 100644
--- a/modules/juce_gui_basics/juce_gui_basics.cpp
+++ b/modules/juce_gui_basics/juce_gui_basics.cpp
@@ -122,6 +122,8 @@ namespace juce
     {
         return Process::isForegroundProcess() || isEmbeddedInForegroundProcess (viewComponent);
     }
+
+    bool isWindowOnCurrentVirtualDesktop (void*);
 }
 
 #include "accessibility/juce_AccessibilityHandler.cpp"
@@ -373,7 +375,56 @@ namespace juce
 }
 
 //==============================================================================
-#if ! JUCE_WINDOWS
+#if JUCE_WINDOWS
+bool juce::isWindowOnCurrentVirtualDesktop (void* x)
+{
+    if (x == nullptr)
+        return false;
+
+    static auto* desktopManager = []
+    {
+        // IVirtualDesktopManager Copied from ShObjdl_core.h, because it may not be defined
+        MIDL_INTERFACE ("a5cd92ff-29be-454c-8d04-d82879fb3f1b")
+        juce_IVirtualDesktopManager : public IUnknown
+        {
+        public:
+            virtual HRESULT STDMETHODCALLTYPE IsWindowOnCurrentVirtualDesktop(
+                 __RPC__in HWND topLevelWindow,
+                 __RPC__out BOOL * onCurrentDesktop) = 0;
+
+            virtual HRESULT STDMETHODCALLTYPE GetWindowDesktopId(
+                 __RPC__in HWND topLevelWindow,
+                 __RPC__out GUID * desktopId) = 0;
+
+            virtual HRESULT STDMETHODCALLTYPE MoveWindowToDesktop(
+                 __RPC__in HWND topLevelWindow,
+                 __RPC__in REFGUID desktopId) = 0;
+        };
+
+        juce_IVirtualDesktopManager* result = nullptr;
+
+        JUCE_BEGIN_IGNORE_WARNINGS_GCC_LIKE ("-Wlanguage-extension-token")
+
+        class DECLSPEC_UUID("aa509086-5ca9-4c25-8f95-589d3c07b48a") juce_VirtualDesktopManager;
+
+        if (SUCCEEDED (CoCreateInstance (__uuidof (juce_VirtualDesktopManager), nullptr, CLSCTX_ALL, IID_PPV_ARGS (&result))))
+            return result;
+
+        JUCE_END_IGNORE_WARNINGS_GCC_LIKE
+
+        return static_cast<juce_IVirtualDesktopManager*> (nullptr);
+    }();
+
+    BOOL current = false;
+
+    if (auto* dm = desktopManager)
+        if (SUCCEEDED (dm->IsWindowOnCurrentVirtualDesktop (static_cast<HWND> (x), &current)))
+            return current != false;
+
+    return true;
+}
+#else
+ bool juce::isWindowOnCurrentVirtualDesktop (void*) { return true; }
  juce::ScopedDPIAwarenessDisabler::ScopedDPIAwarenessDisabler()  { ignoreUnused (previousContext); }
  juce::ScopedDPIAwarenessDisabler::~ScopedDPIAwarenessDisabler() {}
 #endif
diff --git a/modules/juce_gui_basics/misc/juce_DropShadower.cpp b/modules/juce_gui_basics/misc/juce_DropShadower.cpp
index 6decf6d5f7..d8458df7cc 100644
--- a/modules/juce_gui_basics/misc/juce_DropShadower.cpp
+++ b/modules/juce_gui_basics/misc/juce_DropShadower.cpp
@@ -75,7 +75,8 @@ private:
     JUCE_DECLARE_NON_COPYABLE (ShadowWindow)
 };
 
-class ParentVisibilityChangedListener  : public ComponentListener
+class ParentVisibilityChangedListener  : public ComponentListener,
+                                         private Timer
 {
 public:
     ParentVisibilityChangedListener (Component& r, ComponentListener& l)
@@ -83,6 +84,9 @@ public:
     {
         if (auto* firstParent = root->getParentComponent())
             updateParentHierarchy (firstParent);
+
+        if ((SystemStats::getOperatingSystemType() & SystemStats::Windows) != 0)
+            startTimerHz (20);
     }
 
     ~ParentVisibilityChangedListener() override
@@ -146,6 +150,11 @@ private:
         withDifference (observedComponents, lastSeenComponents, [this] (auto& comp) { comp.addComponentListener (this); });
     }
 
+    void timerCallback() override
+    {
+        listener->componentVisibilityChanged (*root);
+    }
+
     Component* root = nullptr;
     ComponentListener* listener = nullptr;
     std::set<ComponentWithWeakReference> observedComponents;
@@ -246,15 +255,11 @@ void DropShadower::updateShadows()
 
     const ScopedValueSetter<bool> setter (reentrant, true);
 
-    if (owner == nullptr)
-    {
-        shadowWindows.clear();
-        return;
-    }
-
-    if (owner->isShowing()
-         && owner->getWidth() > 0 && owner->getHeight() > 0
-         && (Desktop::canUseSemiTransparentWindows() || owner->getParentComponent() != nullptr))
+    if (owner != nullptr
+        && owner->isShowing()
+        && owner->getWidth() > 0 && owner->getHeight() > 0
+        && (Desktop::canUseSemiTransparentWindows() || owner->getParentComponent() != nullptr)
+        && isWindowOnCurrentVirtualDesktop (owner->getWindowHandle()))
     {
         while (shadowWindows.size() < 4)
             shadowWindows.add (new ShadowWindow (owner, shadow));