Merging upstream version 126.0.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

80 files changed, 1386 insertions, 1906 deletions

diff --git a/widget/BasicEvents.h b/widget/BasicEvents.h
index b3707f1cf4..affc58f3be 100644
--- a/widget/BasicEvents.h
+++ b/widget/BasicEvents.h
@@ -440,6 +440,10 @@ class WidgetEvent : public WidgetEventTime {
         mFlags.mCancelable = false;
         mFlags.mBubbles = mFlags.mIsTrusted;
         break;
+      case eLegacyTextEventClass:
+        mFlags.mCancelable = mFlags.mIsTrusted && mMessage == eLegacyTextInput;
+        mFlags.mBubbles = mFlags.mIsTrusted && mMessage == eLegacyTextInput;
+        break;
       case eMouseEventClass:
         mFlags.mCancelable =
             (mMessage != eMouseEnter && mMessage != eMouseLeave);
diff --git a/widget/EventClassList.h b/widget/EventClassList.h
index c8870d84e5..937047e8ba 100644
--- a/widget/EventClassList.h
+++ b/widget/EventClassList.h
@@ -26,6 +26,7 @@ NS_EVENT_CLASS(Widget, CompositionEvent)
 NS_EVENT_CLASS(Widget, QueryContentEvent)
 NS_EVENT_CLASS(Widget, SelectionEvent)
 NS_EVENT_CLASS(Internal, EditorInputEvent)
+NS_EVENT_CLASS(Internal, LegacyTextEvent)
 
 // MouseEvents.h
 NS_EVENT_CLASS(Widget, MouseEventBase)
diff --git a/widget/EventForwards.h b/widget/EventForwards.h
index e6a1ad6274..4a6d796cd1 100644
--- a/widget/EventForwards.h
+++ b/widget/EventForwards.h
@@ -270,9 +270,6 @@ inline bool IsCancelableBeforeInputEvent(EditorInputType aInputType) {
       return true;
     case EditorInputType::eInsertLink:
       return true;
-    case EditorInputType::eDeleteByComposition:
-      MOZ_ASSERT(!StaticPrefs::dom_input_events_conform_to_level_1());
-      return true;
     case EditorInputType::eDeleteCompositionText:
       MOZ_ASSERT(!StaticPrefs::dom_input_events_conform_to_level_1());
       return false;
diff --git a/widget/EventMessageList.h b/widget/EventMessageList.h
index f42c1e3b2c..4247403770 100644
--- a/widget/EventMessageList.h
+++ b/widget/EventMessageList.h
@@ -432,6 +432,9 @@ NS_EVENT_MESSAGE_FIRST_LAST(eGamepadEvent, eGamepadButtonDown,
 NS_EVENT_MESSAGE(eEditorInput)
 NS_EVENT_MESSAGE(eEditorBeforeInput)
 
+// textInput event which is a default action of beforeinput
+NS_EVENT_MESSAGE(eLegacyTextInput)
+
 // selection events
 NS_EVENT_MESSAGE(eSelectStart)
 NS_EVENT_MESSAGE(eSelectionChange)
@@ -450,11 +453,6 @@ NS_EVENT_MESSAGE(eToggle)
 NS_EVENT_MESSAGE(eClose)
 NS_EVENT_MESSAGE(eCancel)
 
-// Marquee element events.
-NS_EVENT_MESSAGE(eMarqueeBounce)
-NS_EVENT_MESSAGE(eMarqueeStart)
-NS_EVENT_MESSAGE(eMarqueeFinish)
-
 NS_EVENT_MESSAGE(eScrollend)
 
 #ifdef UNDEF_NS_EVENT_MESSAGE_FIRST_LAST
diff --git a/widget/InitData.h b/widget/InitData.h
index aed5e0a551..a073362065 100644
--- a/widget/InitData.h
+++ b/widget/InitData.h
@@ -17,7 +17,6 @@ enum class WindowType : uint8_t {
   TopLevel,   // default top level window
   Dialog,     // top level window but usually handled differently
               // by the OS
-  Sheet,      // MacOSX sheet (special dialog class)
   Popup,      // used for combo boxes, etc
   Child,      // child windows (contained inside a window on the
               // desktop (has no border))
diff --git a/widget/InputData.cpp b/widget/InputData.cpp
index 3d1695dd8e..8f06a51c1c 100644
--- a/widget/InputData.cpp
+++ b/widget/InputData.cpp
@@ -303,6 +303,9 @@ MouseInput::MouseInput(const WidgetMouseEventBase& aMouseEvent)
     case eMouseHitTest:
       mType = MOUSE_HITTEST;
       break;
+    case eContextMenu:
+      mType = MOUSE_CONTEXTMENU;
+      break;
     default:
       MOZ_ASSERT_UNREACHABLE("Mouse event type not supported");
       break;
@@ -364,6 +367,9 @@ WidgetMouseEvent MouseInput::ToWidgetEvent(nsIWidget* aWidget) const {
     case MOUSE_HITTEST:
       msg = eMouseHitTest;
       break;
+    case MOUSE_CONTEXTMENU:
+      msg = eContextMenu;
+      break;
     default:
       MOZ_ASSERT_UNREACHABLE(
           "Did not assign a type to WidgetMouseEvent in MouseInput");
diff --git a/widget/InputData.h b/widget/InputData.h
index 855cfcd178..fa011f8451 100644
--- a/widget/InputData.h
+++ b/widget/InputData.h
@@ -275,7 +275,8 @@ class MouseInput : public InputData {
       MOUSE_WIDGET_ENTER,
       MOUSE_WIDGET_EXIT,
       MOUSE_HITTEST,
-      MOUSE_EXPLORE_BY_TOUCH
+      MOUSE_EXPLORE_BY_TOUCH,
+      MOUSE_CONTEXTMENU
   ));
 
   MOZ_DEFINE_ENUM_AT_CLASS_SCOPE(
diff --git a/widget/LSBUtils.cpp b/widget/LSBUtils.cpp
index 9ebffacd7e..718c43d26e 100644
--- a/widget/LSBUtils.cpp
+++ b/widget/LSBUtils.cpp
@@ -45,6 +45,7 @@ bool GetOSRelease(nsACString& aDistributor, nsACString& aDescription,
   bool seen_id = false, seen_pretty_name = false, seen_version_id = false;
   std::string rawline;
   nsAutoCString name;
+  nsAutoCString build_id;
   while (std::getline(stream, rawline)) {
     std::string_view line(rawline);
     size_t pos = line.find('=');
@@ -68,6 +69,8 @@ bool GetOSRelease(nsACString& aDistributor, nsACString& aDescription,
         if (ExtractAndSetValue(aDescription, value)) seen_pretty_name = true;
       } else if (key == "VERSION_ID") {
         if (ExtractAndSetValue(aRelease, value)) seen_version_id = true;
+      } else if (key == "BUILD_ID") {
+        ExtractAndSetValue(build_id, value);
       } else if (key == "VERSION_CODENAME") {
         ExtractAndSetValue(aCodename, value);
       }
@@ -77,6 +80,11 @@ bool GetOSRelease(nsACString& aDistributor, nsACString& aDescription,
   if (seen_id && !name.IsEmpty() && name.EqualsIgnoreCase(aDistributor)) {
     aDistributor = name;
   }
+  // If VERSION_ID is not set but BUILD_ID is, use BUILD_ID.
+  if (!seen_version_id && !build_id.IsEmpty()) {
+    aRelease = build_id;
+    seen_version_id = true;
+  }
   // Only consider our work done if we've seen at least ID, PRETTY_NAME and
   // VERSION_ID.
   return seen_id && seen_pretty_name && seen_version_id;
diff --git a/widget/LookAndFeel.h b/widget/LookAndFeel.h
index 0cab187410..13219ff54b 100644
--- a/widget/LookAndFeel.h
+++ b/widget/LookAndFeel.h
@@ -53,8 +53,6 @@ class LookAndFeel {
     CaretBlinkCount,
     // pixel width of caret
     CaretWidth,
-    // show the caret when text is selected?
-    ShowCaretDuringSelection,
     // select textfields when focused via tab/accesskey?
     SelectTextfieldsOnKeyFocus,
     // delay before submenus open
@@ -119,6 +117,9 @@ class LookAndFeel {
      */
     MacRTL,
 
+    /* Native macOS titlebar height. */
+    MacTitlebarHeight,
+
     /*
      * AlertNotificationOrigin indicates from which corner of the
      * screen alerts slide in, and from which direction (horizontal/vertical).
@@ -186,6 +187,7 @@ class LookAndFeel {
      */
     ContextMenuOffsetVertical,
     ContextMenuOffsetHorizontal,
+    TooltipOffsetVertical,
 
     /*
      * A boolean value indicating whether client-side decorations are
@@ -299,7 +301,6 @@ class LookAndFeel {
      * 1: High
      */
     DynamicRange,
-    VideoDynamicRange,
 
     /** Whether XUL panel animations are enabled. */
     PanelAnimations,
@@ -321,6 +322,11 @@ class LookAndFeel {
     return GetInt(IntID::UseOverlayScrollbars);
   }
 
+  static constexpr int32_t kDefaultTooltipOffset = 21;
+  static int32_t TooltipOffsetVertical() {
+    return GetInt(IntID::TooltipOffsetVertical, kDefaultTooltipOffset);
+  }
+
   // Returns keyCode value of a modifier key which is used for accesskey.
   // Returns 0 if the platform doesn't support access key.
   static uint32_t GetMenuAccessKey();
diff --git a/widget/Screen.cpp b/widget/Screen.cpp
index 71a1624624..ccc78a9413 100644
--- a/widget/Screen.cpp
+++ b/widget/Screen.cpp
@@ -30,7 +30,7 @@ Screen::Screen(LayoutDeviceIntRect aRect, LayoutDeviceIntRect aAvailRect,
                uint32_t aPixelDepth, uint32_t aColorDepth,
                uint32_t aRefreshRate, DesktopToLayoutDeviceScale aContentsScale,
                CSSToLayoutDeviceScale aDefaultCssScale, float aDPI,
-               IsPseudoDisplay aIsPseudoDisplay,
+               IsPseudoDisplay aIsPseudoDisplay, IsHDR aIsHDR,
                hal::ScreenOrientation aOrientation,
                OrientationAngle aOrientationAngle)
     : mRect(aRect),
@@ -45,7 +45,8 @@ Screen::Screen(LayoutDeviceIntRect aRect, LayoutDeviceIntRect aAvailRect,
       mDPI(aDPI),
       mScreenOrientation(EffectiveOrientation(aOrientation, aRect)),
       mOrientationAngle(aOrientationAngle),
-      mIsPseudoDisplay(aIsPseudoDisplay == IsPseudoDisplay::Yes) {}
+      mIsPseudoDisplay(aIsPseudoDisplay == IsPseudoDisplay::Yes),
+      mIsHDR(aIsHDR == IsHDR::Yes) {}
 
 Screen::Screen(const dom::ScreenDetails& aScreen)
     : mRect(aScreen.rect()),
@@ -60,7 +61,8 @@ Screen::Screen(const dom::ScreenDetails& aScreen)
       mDPI(aScreen.dpi()),
       mScreenOrientation(aScreen.orientation()),
       mOrientationAngle(aScreen.orientationAngle()),
-      mIsPseudoDisplay(aScreen.isPseudoDisplay()) {}
+      mIsPseudoDisplay(aScreen.isPseudoDisplay()),
+      mIsHDR(aScreen.isHDR()) {}
 
 Screen::Screen(const Screen& aOther)
     : mRect(aOther.mRect),
@@ -75,13 +77,14 @@ Screen::Screen(const Screen& aOther)
       mDPI(aOther.mDPI),
       mScreenOrientation(aOther.mScreenOrientation),
       mOrientationAngle(aOther.mOrientationAngle),
-      mIsPseudoDisplay(aOther.mIsPseudoDisplay) {}
+      mIsPseudoDisplay(aOther.mIsPseudoDisplay),
+      mIsHDR(aOther.mIsHDR) {}
 
 dom::ScreenDetails Screen::ToScreenDetails() const {
   return dom::ScreenDetails(
       mRect, mRectDisplayPix, mAvailRect, mAvailRectDisplayPix, mPixelDepth,
       mColorDepth, mRefreshRate, mContentsScale, mDefaultCssScale, mDPI,
-      mScreenOrientation, mOrientationAngle, mIsPseudoDisplay);
+      mScreenOrientation, mOrientationAngle, mIsPseudoDisplay, mIsHDR);
 }
 
 NS_IMETHODIMP
diff --git a/widget/Screen.h b/widget/Screen.h
index f3f8b4a628..ca2efa1f59 100644
--- a/widget/Screen.h
+++ b/widget/Screen.h
@@ -26,12 +26,13 @@ class Screen final : public nsIScreen {
 
   using OrientationAngle = uint16_t;
   enum class IsPseudoDisplay : bool { No, Yes };
+  enum class IsHDR : bool { No, Yes };
 
   Screen(LayoutDeviceIntRect aRect, LayoutDeviceIntRect aAvailRect,
          uint32_t aPixelDepth, uint32_t aColorDepth, uint32_t aRefreshRate,
          DesktopToLayoutDeviceScale aContentsScale,
          CSSToLayoutDeviceScale aDefaultCssScale, float aDpi, IsPseudoDisplay,
-         hal::ScreenOrientation = hal::ScreenOrientation::None,
+         IsHDR, hal::ScreenOrientation = hal::ScreenOrientation::None,
          OrientationAngle = 0);
   explicit Screen(const dom::ScreenDetails& aScreenDetails);
   Screen(const Screen& aOther);
@@ -60,6 +61,8 @@ class Screen final : public nsIScreen {
   enum class IncludeOSZoom : bool { No, Yes };
   CSSToLayoutDeviceScale GetCSSToLayoutDeviceScale(IncludeOSZoom) const;
 
+  bool GetIsHDR() const { return mIsHDR; }
+
  private:
   virtual ~Screen() = default;
 
@@ -76,6 +79,7 @@ class Screen final : public nsIScreen {
   const hal::ScreenOrientation mScreenOrientation;
   const OrientationAngle mOrientationAngle;
   const bool mIsPseudoDisplay;
+  const bool mIsHDR;
 };
 
 }  // namespace widget
diff --git a/widget/ScreenManager.cpp b/widget/ScreenManager.cpp
index 58e20806eb..84d7316af7 100644
--- a/widget/ScreenManager.cpp
+++ b/widget/ScreenManager.cpp
@@ -139,7 +139,8 @@ already_AddRefed<Screen> ScreenManager::ScreenForRect(
     auto screen = MakeRefPtr<Screen>(
         LayoutDeviceIntRect(), LayoutDeviceIntRect(), 0, 0, 0,
         DesktopToLayoutDeviceScale(), CSSToLayoutDeviceScale(), 96 /* dpi */,
-        Screen::IsPseudoDisplay::No, hal::ScreenOrientation::None, 0);
+        Screen::IsPseudoDisplay::No, Screen::IsHDR::No,
+        hal::ScreenOrientation::None, 0);
     return screen.forget();
   }
 
@@ -219,10 +220,11 @@ already_AddRefed<Screen> ScreenManager::GetPrimaryScreen() {
   if (mScreenList.IsEmpty()) {
     MOZ_LOG(sScreenLog, LogLevel::Warning,
             ("No screen available. This can happen in xpcshell."));
-    return MakeAndAddRef<Screen>(
-        LayoutDeviceIntRect(), LayoutDeviceIntRect(), 0, 0, 0,
-        DesktopToLayoutDeviceScale(), CSSToLayoutDeviceScale(), 96 /* dpi */,
-        Screen::IsPseudoDisplay::No, hal::ScreenOrientation::None, 0);
+    return MakeAndAddRef<Screen>(LayoutDeviceIntRect(), LayoutDeviceIntRect(),
+                                 0, 0, 0, DesktopToLayoutDeviceScale(),
+                                 CSSToLayoutDeviceScale(), 96 /* dpi */,
+                                 Screen::IsPseudoDisplay::No, Screen::IsHDR::No,
+                                 hal::ScreenOrientation::None, 0);
   }
 
   return do_AddRef(mScreenList[0]);
diff --git a/widget/TextEvents.h b/widget/TextEvents.h
index 71d2e656e2..3f42561c75 100644
--- a/widget/TextEvents.h
+++ b/widget/TextEvents.h
@@ -1442,13 +1442,8 @@ class WidgetSelectionEvent : public WidgetGUIEvent {
  ******************************************************************************/
 
 class InternalEditorInputEvent : public InternalUIEvent {
- private:
-  InternalEditorInputEvent()
-      : mData(VoidString()),
-        mInputType(EditorInputType::eUnknown),
-        mIsComposing(false) {}
-
  public:
+  InternalEditorInputEvent() = delete;
   virtual InternalEditorInputEvent* AsEditorInputEvent() override {
     return this;
   }
@@ -1457,9 +1452,7 @@ class InternalEditorInputEvent : public InternalUIEvent {
                            nsIWidget* aWidget = nullptr,
                            const WidgetEventTime* aTime = nullptr)
       : InternalUIEvent(aIsTrusted, aMessage, aWidget, eEditorInputEventClass,
-                        aTime),
-        mData(VoidString()),
-        mInputType(EditorInputType::eUnknown) {}
+                        aTime) {}
 
   virtual WidgetEvent* Duplicate() const override {
     MOZ_ASSERT(mClass == eEditorInputEventClass,
@@ -1472,13 +1465,13 @@ class InternalEditorInputEvent : public InternalUIEvent {
     return result;
   }
 
-  nsString mData;
+  nsString mData = VoidString();
   RefPtr<dom::DataTransfer> mDataTransfer;
   OwningNonNullStaticRangeArray mTargetRanges;
 
-  EditorInputType mInputType;
+  EditorInputType mInputType = EditorInputType::eUnknown;
 
-  bool mIsComposing;
+  bool mIsComposing = false;
 
   void AssignEditorInputEventData(const InternalEditorInputEvent& aEvent,
                                   bool aCopyTargets) {
@@ -1502,10 +1495,51 @@ class InternalEditorInputEvent : public InternalUIEvent {
 
  private:
   static const char16_t* const kInputTypeNames[];
-  typedef nsTHashMap<nsStringHashKey, EditorInputType> InputTypeHashtable;
+  using InputTypeHashtable = nsTHashMap<nsStringHashKey, EditorInputType>;
   static InputTypeHashtable* sInputTypeHashtable;
 };
 
+/******************************************************************************
+ * mozilla::InternalLegacyTextEvent
+ ******************************************************************************/
+
+class InternalLegacyTextEvent : public InternalUIEvent {
+ public:
+  InternalLegacyTextEvent() = delete;
+
+  virtual InternalLegacyTextEvent* AsLegacyTextEvent() override { return this; }
+
+  InternalLegacyTextEvent(bool aIsTrusted, EventMessage aMessage,
+                          nsIWidget* aWidget = nullptr,
+                          const WidgetEventTime* aTime = nullptr)
+      : InternalUIEvent(aIsTrusted, aMessage, aWidget, eLegacyTextEventClass,
+                        aTime) {}
+
+  virtual WidgetEvent* Duplicate() const override {
+    MOZ_ASSERT(mClass == eLegacyTextEventClass,
+               "Duplicate() must be overridden by sub class");
+    // Not copying widget, it is a weak reference.
+    InternalLegacyTextEvent* result =
+        new InternalLegacyTextEvent(false, mMessage, nullptr, this);
+    result->AssignLegacyTextEventData(*this, true);
+    result->mFlags = mFlags;
+    return result;
+  }
+
+  nsString mData;
+  RefPtr<dom::DataTransfer> mDataTransfer;
+  EditorInputType mInputType = EditorInputType::eUnknown;
+
+  void AssignLegacyTextEventData(const InternalLegacyTextEvent& aEvent,
+                                 bool aCopyTargets) {
+    AssignUIEventData(aEvent, aCopyTargets);
+
+    mData = aEvent.mData;
+    mDataTransfer = aEvent.mDataTransfer;
+    mInputType = aEvent.mInputType;
+  }
+};
+
 }  // namespace mozilla
 
 #endif  // mozilla_TextEvents_h__
diff --git a/widget/Theme.cpp b/widget/Theme.cpp
index 1fcd3d4bc3..15bf68ec01 100644
--- a/widget/Theme.cpp
+++ b/widget/Theme.cpp
@@ -296,6 +296,9 @@ std::pair<sRGBColor, sRGBColor> Theme::ComputeButtonColors(
   bool isHovered = aState.HasState(ElementState::HOVER);
 
   nscolor backgroundColor = [&] {
+    if (aState.HasState(ElementState::AUTOFILL)) {
+      return aColors.SystemNs(StyleSystemColor::MozAutofillBackground);
+    }
     if (isDisabled) {
       return aColors.SystemNs(StyleSystemColor::MozButtondisabledface);
     }
@@ -308,12 +311,6 @@ std::pair<sRGBColor, sRGBColor> Theme::ComputeButtonColors(
     return aColors.SystemNs(StyleSystemColor::Buttonface);
   }();
 
-  if (aState.HasState(ElementState::AUTOFILL)) {
-    backgroundColor = NS_ComposeColors(
-        backgroundColor,
-        aColors.SystemNs(StyleSystemColor::MozAutofillBackground));
-  }
-
   const sRGBColor borderColor =
       ComputeBorderColor(aState, aColors, OutlineCoversBorder::Yes);
   return std::make_pair(sRGBColor::FromABGR(backgroundColor), borderColor);
@@ -323,18 +320,15 @@ std::pair<sRGBColor, sRGBColor> Theme::ComputeTextfieldColors(
     const ElementState& aState, const Colors& aColors,
     OutlineCoversBorder aOutlineCoversBorder) {
   nscolor backgroundColor = [&] {
+    if (aState.HasState(ElementState::AUTOFILL)) {
+      return aColors.SystemNs(StyleSystemColor::MozAutofillBackground);
+    }
     if (aState.HasState(ElementState::DISABLED)) {
       return aColors.SystemNs(StyleSystemColor::MozDisabledfield);
     }
     return aColors.SystemNs(StyleSystemColor::Field);
   }();
 
-  if (aState.HasState(ElementState::AUTOFILL)) {
-    backgroundColor = NS_ComposeColors(
-        backgroundColor,
-        aColors.SystemNs(StyleSystemColor::MozAutofillBackground));
-  }
-
   const sRGBColor borderColor =
       ComputeBorderColor(aState, aColors, aOutlineCoversBorder);
   return std::make_pair(sRGBColor::FromABGR(backgroundColor), borderColor);
diff --git a/widget/android/EventDispatcher.cpp b/widget/android/EventDispatcher.cpp
index 6e414c11ce..2054d822d7 100644
--- a/widget/android/EventDispatcher.cpp
+++ b/widget/android/EventDispatcher.cpp
@@ -21,12 +21,6 @@
 #include "mozilla/java/EventCallbackWrappers.h"
 #include "mozilla/jni/GeckoBundleUtils.h"
 
-// Disable the C++ 2a warning. See bug #1509926
-#if defined(__clang__)
-#  pragma clang diagnostic push
-#  pragma clang diagnostic ignored "-Wc++2a-compat"
-#endif
-
 namespace mozilla {
 namespace widget {
 
@@ -770,7 +764,3 @@ nsresult EventDispatcher::UnboxBundle(JSContext* aCx, jni::Object::Param aData,
 
 }  // namespace widget
 }  // namespace mozilla
-
-#if defined(__clang__)
-#  pragma clang diagnostic pop
-#endif
diff --git a/widget/android/GfxInfo.cpp b/widget/android/GfxInfo.cpp
index 6e6d3bf47b..267beaf330 100644
--- a/widget/android/GfxInfo.cpp
+++ b/widget/android/GfxInfo.cpp
@@ -667,6 +667,14 @@ nsresult GfxInfo::GetFeatureStatusImpl(
     return NS_OK;
   }
 
+  if (aFeature == FEATURE_WEBGPU) {
+    // Ensure WebGPU is disabled by default on Android until it is better
+    // tested.
+    *aStatus = nsIGfxInfo::FEATURE_BLOCKED_DEVICE;
+    aFailureId = "FEATURE_FAILURE_WEBGPU_ANDROID";
+    return NS_OK;
+  }
+
   return GfxInfoBase::GetFeatureStatusImpl(
       aFeature, aStatus, aSuggestedDriverVersion, aDriverInfo, aFailureId, &os);
 }
diff --git a/widget/android/ScreenHelperAndroid.cpp b/widget/android/ScreenHelperAndroid.cpp
index 33c91fe6e0..141b38e01b 100644
--- a/widget/android/ScreenHelperAndroid.cpp
+++ b/widget/android/ScreenHelperAndroid.cpp
@@ -38,14 +38,15 @@ static already_AddRefed<Screen> MakePrimaryScreen() {
   uint32_t depth = java::GeckoAppShell::GetScreenDepth();
   float density = java::GeckoAppShell::GetDensity();
   float dpi = java::GeckoAppShell::GetDpi();
+  bool isHDR = false;  // Bug 1884960: report this accurately
   auto orientation =
       hal::ScreenOrientation(java::GeckoAppShell::GetScreenOrientation());
   uint16_t angle = java::GeckoAppShell::GetScreenAngle();
   float refreshRate = java::GeckoAppShell::GetScreenRefreshRate();
-  return MakeAndAddRef<Screen>(bounds, bounds, depth, depth, refreshRate,
-                               DesktopToLayoutDeviceScale(density),
-                               CSSToLayoutDeviceScale(1.0f), dpi,
-                               Screen::IsPseudoDisplay::No, orientation, angle);
+  return MakeAndAddRef<Screen>(
+      bounds, bounds, depth, depth, refreshRate,
+      DesktopToLayoutDeviceScale(density), CSSToLayoutDeviceScale(1.0f), dpi,
+      Screen::IsPseudoDisplay::No, Screen::IsHDR(isHDR), orientation, angle);
 }
 
 ScreenHelperAndroid::ScreenHelperAndroid() {
diff --git a/widget/android/nsLookAndFeel.cpp b/widget/android/nsLookAndFeel.cpp
index 6d9f8c634f..45c556f6d1 100644
--- a/widget/android/nsLookAndFeel.cpp
+++ b/widget/android/nsLookAndFeel.cpp
@@ -253,6 +253,7 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aColorScheme,
       break;
     case ColorID::Marktext:
     case ColorID::Mark:
+    case ColorID::MozAutofillBackground:
     case ColorID::SpellCheckerUnderline:
       aColor = GetStandinForNativeColor(aID, aColorScheme);
       break;
@@ -298,10 +299,6 @@ nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
       aResult = 1;
       break;
 
-    case IntID::ShowCaretDuringSelection:
-      aResult = 0;
-      break;
-
     case IntID::SelectTextfieldsOnKeyFocus:
       // Select textfield content when focused by kbd
       // used by EventStateManager::sTextfieldSelectModel
diff --git a/widget/android/nsWindow.cpp b/widget/android/nsWindow.cpp
index e9756c3f92..a654c8e848 100644
--- a/widget/android/nsWindow.cpp
+++ b/widget/android/nsWindow.cpp
@@ -609,6 +609,22 @@ class NPZCSupport final
     PostInputEvent([input = std::move(input), result](nsWindow* window) {
       WidgetMouseEvent mouseEvent = input.ToWidgetEvent(window);
       window->ProcessUntransformedAPZEvent(&mouseEvent, result);
+      if (MouseInput::SECONDARY_BUTTON == input.mButtonType) {
+        if ((StaticPrefs::ui_context_menus_after_mouseup() &&
+             MouseInput::MOUSE_UP == input.mType) ||
+            (!StaticPrefs::ui_context_menus_after_mouseup() &&
+             MouseInput::MOUSE_DOWN == input.mType)) {
+          MouseInput contextMenu = input;
+
+          // Actually we don't dispatch context menu event to APZ since we don't
+          // handle it on APZ yet. If handling it, we need to consider how to
+          // dispatch it on APZ thread. It may cause a race condition.
+          contextMenu.mType = MouseInput::MOUSE_CONTEXTMENU;
+
+          WidgetMouseEvent contextMenuEvent = contextMenu.ToWidgetEvent(window);
+          window->ProcessUntransformedAPZEvent(&contextMenuEvent, result);
+        }
+      }
     });
 
     switch (result.GetStatus()) {
diff --git a/widget/cocoa/MacThemeGeometryType.h b/widget/cocoa/MacThemeGeometryType.h
index 4691dbdec2..91879503e1 100644
--- a/widget/cocoa/MacThemeGeometryType.h
+++ b/widget/cocoa/MacThemeGeometryType.h
@@ -7,11 +7,7 @@
 
 enum MacThemeGeometryType {
   eThemeGeometryTypeTitlebar = 1,
-  eThemeGeometryTypeToolbar,
-  eThemeGeometryTypeToolbox,
   eThemeGeometryTypeWindowButtons,
-  eThemeGeometryTypeMenu,
-  eThemeGeometryTypeTooltip,
 };
 
 #endif
diff --git a/widget/cocoa/ScreenHelperCocoa.mm b/widget/cocoa/ScreenHelperCocoa.mm
index 57e1313320..2f1408e345 100644
--- a/widget/cocoa/ScreenHelperCocoa.mm
+++ b/widget/cocoa/ScreenHelperCocoa.mm
@@ -9,6 +9,7 @@
 #import <Cocoa/Cocoa.h>
 
 #include "mozilla/Logging.h"
+#include "nsCocoaFeatures.h"
 #include "nsCocoaUtils.h"
 #include "nsObjCExceptions.h"
 
@@ -109,6 +110,26 @@ static already_AddRefed<Screen> MakeScreen(NSScreen* aScreen) {
     pixelDepth = MAX_REPORTED_PIXEL_DEPTH;
   }
 
+  // What's the maximum color component value this screen can display? This
+  // is a reasonable stand-in for measuring peak brightness.
+  CGFloat componentValueMax =
+      aScreen.maximumPotentialExtendedDynamicRangeColorComponentValue;
+
+  // Should we treat this as HDR? Based on spec at
+  // https://drafts.csswg.org/mediaqueries-5/#dynamic-range, we'll consider it
+  // HDR if it has pixel depth greater than 24, and if has high peak brightness,
+  // which we measure by checking if it can represent component values greater
+  // than 1.0.
+  //
+  // Also, on HDR screens, users may want to force SDR by setting a different
+  // colorspace, for example by using the "Photography (P3 D65)" preset. In that
+  // case, componentValueMax will be 1.0 and we want to treat the display as
+  // SDR.
+  bool isHDR = pixelDepth > 24 && componentValueMax > 1.0;
+
+  // Double-check HDR against the platform capabilities.
+  isHDR &= nsCocoaFeatures::OnBigSurOrLater();
+
   float dpi = 96.0f;
   CGDirectDisplayID displayID =
       [[[aScreen deviceDescription] objectForKey:@"NSScreenNumber"] intValue];
@@ -125,9 +146,10 @@ static already_AddRefed<Screen> MakeScreen(NSScreen* aScreen) {
   // Getting the refresh rate is a little hard on OS X. We could use
   // CVDisplayLinkGetNominalOutputVideoRefreshPeriod, but that's a little
   // involved. Ideally we could query it from vsync. For now, we leave it out.
-  RefPtr<Screen> screen = new Screen(rect, availRect, pixelDepth, pixelDepth, 0,
-                                     contentsScaleFactor, defaultCssScaleFactor,
-                                     dpi, Screen::IsPseudoDisplay::No);
+  RefPtr<Screen> screen =
+      new Screen(rect, availRect, pixelDepth, pixelDepth, 0,
+                 contentsScaleFactor, defaultCssScaleFactor, dpi,
+                 Screen::IsPseudoDisplay::No, Screen::IsHDR(isHDR));
   return screen.forget();
 
   NS_OBJC_END_TRY_BLOCK_RETURN(nullptr);
diff --git a/widget/cocoa/TextInputHandler.mm b/widget/cocoa/TextInputHandler.mm
index 1d96a3ce82..046f1c46be 100644
--- a/widget/cocoa/TextInputHandler.mm
+++ b/widget/cocoa/TextInputHandler.mm
@@ -10,6 +10,7 @@
 
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/AutoRestore.h"
+#include "mozilla/MacStringHelpers.h"
 #include "mozilla/MiscEvents.h"
 #include "mozilla/MouseEvents.h"
 #include "mozilla/StaticPrefs_intl.h"
@@ -321,13 +322,13 @@ static const char* GetCharacters(const nsAString& aString) {
   }
 
   // the result will be freed automatically by cocoa.
-  NSString* result = nsCocoaUtils::ToNSString(escapedStr);
+  NSString* result = XPCOMStringToNSString(escapedStr);
   return [result UTF8String];
 }
 
 static const char* GetCharacters(const NSString* aString) {
   nsAutoString str;
-  nsCocoaUtils::GetStringForNSString(aString, str);
+  CopyNSStringToXPCOMString(aString, str);
   return GetCharacters(str);
 }
 
@@ -835,7 +836,7 @@ bool TISInputSourceWrapper::GetStringProperty(const CFStringRef aKey,
                                               nsAString& aStr) {
   CFStringRef str;
   GetStringProperty(aKey, str);
-  nsCocoaUtils::GetStringForNSString((const NSString*)str, aStr);
+  CopyNSStringToXPCOMString((const NSString*)str, aStr);
   return !aStr.IsEmpty();
 }
 
@@ -883,8 +884,7 @@ bool TISInputSourceWrapper::GetPrimaryLanguage(nsAString& aPrimaryLanguage) {
   NS_ENSURE_TRUE(mInputSource, false);
   CFStringRef primaryLanguage;
   NS_ENSURE_TRUE(GetPrimaryLanguage(primaryLanguage), false);
-  nsCocoaUtils::GetStringForNSString((const NSString*)primaryLanguage,
-                                     aPrimaryLanguage);
+  CopyNSStringToXPCOMString((const NSString*)primaryLanguage, aPrimaryLanguage);
   return !aPrimaryLanguage.IsEmpty();
 }
 
@@ -985,7 +985,7 @@ void TISInputSourceWrapper::ComputeInsertStringForCharCode(
     } else {
       // If the caller isn't sure what string will be input, let's use
       // characters of NSEvent.
-      nsCocoaUtils::GetStringForNSString([aNativeKeyEvent characters], aResult);
+      CopyNSStringToXPCOMString([aNativeKeyEvent characters], aResult);
     }
 
     // If control key is pressed and the eventChars is a non-printable control
@@ -1156,8 +1156,8 @@ void TISInputSourceWrapper::InitKeyEvent(NSEvent* aNativeKeyEvent,
     // non-ASCII capable layout to ASCII capable, or from Dvorak to QWERTY.
     // KeyboardEvent.key value should be the switched layout's character.
     else if (aKeyEvent.IsMeta()) {
-      nsCocoaUtils::GetStringForNSString([aNativeKeyEvent characters],
-                                         aKeyEvent.mKeyValue);
+      CopyNSStringToXPCOMString([aNativeKeyEvent characters],
+                                aKeyEvent.mKeyValue);
     }
     // If control key is pressed, some keys may produce printable character via
     // [aNativeKeyEvent characters].  Otherwise, translate input character of
@@ -1188,8 +1188,8 @@ void TISInputSourceWrapper::InitKeyEvent(NSEvent* aNativeKeyEvent,
           [aNativeKeyEvent modifierFlags]);
       aKeyEvent.mKeyValue = TranslateToChar(nativeKeyCode, state, kbType);
     } else {
-      nsCocoaUtils::GetStringForNSString([aNativeKeyEvent characters],
-                                         aKeyEvent.mKeyValue);
+      CopyNSStringToXPCOMString([aNativeKeyEvent characters],
+                                aKeyEvent.mKeyValue);
       // If the key value is empty, the event may be a dead key event.
       // If TranslateToChar() returns non-zero value, that means that
       // the key may input a character with different dead key state.
@@ -1207,8 +1207,8 @@ void TISInputSourceWrapper::InitKeyEvent(NSEvent* aNativeKeyEvent,
     if (aKeyEvent.mKeyNameIndex == KEY_NAME_INDEX_USE_STRING &&
         (aKeyEvent.mKeyValue.IsEmpty() ||
          IsControlChar(aKeyEvent.mKeyValue[0]))) {
-      nsCocoaUtils::GetStringForNSString(
-          [aNativeKeyEvent charactersIgnoringModifiers], aKeyEvent.mKeyValue);
+      CopyNSStringToXPCOMString([aNativeKeyEvent charactersIgnoringModifiers],
+                                aKeyEvent.mKeyValue);
       // But don't expose it if it's a control character.
       if (!aKeyEvent.mKeyValue.IsEmpty() &&
           IsControlChar(aKeyEvent.mKeyValue[0])) {
@@ -1243,7 +1243,7 @@ void TISInputSourceWrapper::WillDispatchKeyboardEvent(
 
   if (MOZ_LOG_TEST(gKeyLog, LogLevel::Info)) {
     nsAutoString chars;
-    nsCocoaUtils::GetStringForNSString([aNativeKeyEvent characters], chars);
+    CopyNSStringToXPCOMString([aNativeKeyEvent characters], chars);
     NS_ConvertUTF16toUTF8 utf8Chars(chars);
     char16_t uniChar = static_cast<char16_t>(aKeyEvent.mCharCode);
     MOZ_LOG(
@@ -2428,7 +2428,7 @@ void TextInputHandler::InsertText(NSString* aString,
   NSRange selectedRange = SelectedRange();
 
   nsAutoString str;
-  nsCocoaUtils::GetStringForNSString(aString, str);
+  CopyNSStringToXPCOMString(aString, str);
 
   AutoInsertStringClearer clearer(currentKeyEvent);
   if (currentKeyEvent) {
@@ -3849,7 +3849,7 @@ bool IMEInputHandler::DispatchCompositionCommitEvent(
       mSelectedRange.location += aCommitString->Length();
     } else if (mIMECompositionString) {
       nsAutoString commitString;
-      nsCocoaUtils::GetStringForNSString(mIMECompositionString, commitString);
+      CopyNSStringToXPCOMString(mIMECompositionString, commitString);
       mSelectedRange.location += commitString.Length();
     }
     mSelectedRange.length = 0;
@@ -4037,7 +4037,7 @@ void IMEInputHandler::InsertTextAsCommittingComposition(
   }
 
   nsString str;
-  nsCocoaUtils::GetStringForNSString(aString, str);
+  CopyNSStringToXPCOMString(aString, str);
 
   if (!IsIMEComposing()) {
     MOZ_DIAGNOSTIC_ASSERT(!str.IsEmpty());
@@ -4171,7 +4171,7 @@ void IMEInputHandler::SetMarkedText(NSAttributedString* aAttrString,
   }
 
   nsString str;
-  nsCocoaUtils::GetStringForNSString([aAttrString string], str);
+  CopyNSStringToXPCOMString([aAttrString string], str);
 
   mMarkedRange.length = str.Length();
 
@@ -4272,7 +4272,7 @@ NSAttributedString* IMEInputHandler::GetAttributedSubstringFromRange(
 
     if (MOZ_LOG_TEST(gIMELog, LogLevel::Info)) {
       nsAutoString str;
-      nsCocoaUtils::GetStringForNSString(nsstr, str);
+      CopyNSStringToXPCOMString(nsstr, str);
       MOZ_LOG(gIMELog, LogLevel::Info,
               ("%p   IMEInputHandler::GetAttributedSubstringFromRange, "
                "computed with mIMECompositionString (result string=\"%s\")",
@@ -5051,18 +5051,17 @@ nsresult TextInputHandlerBase::SynthesizeNativeKeyEvent(
   bool sendFlagsChangedEvent = IsModifierKey(aNativeKeyCode);
   NSEventType eventType =
       sendFlagsChangedEvent ? NSEventTypeFlagsChanged : NSEventTypeKeyDown;
-  NSEvent* downEvent =
-      [NSEvent keyEventWithType:eventType
-                             location:NSMakePoint(0, 0)
-                        modifierFlags:modifierFlags
-                            timestamp:0
-                         windowNumber:windowNumber
-                              context:nil
-                           characters:nsCocoaUtils::ToNSString(aCharacters)
-          charactersIgnoringModifiers:nsCocoaUtils::ToNSString(
-                                          aUnmodifiedCharacters)
-                            isARepeat:NO
-                              keyCode:aNativeKeyCode];
+  NSEvent* downEvent = [NSEvent
+                 keyEventWithType:eventType
+                         location:NSMakePoint(0, 0)
+                    modifierFlags:modifierFlags
+                        timestamp:0
+                     windowNumber:windowNumber
+                          context:nil
+                       characters:XPCOMStringToNSString(aCharacters)
+      charactersIgnoringModifiers:XPCOMStringToNSString(aUnmodifiedCharacters)
+                        isARepeat:NO
+                          keyCode:aNativeKeyCode];
 
   NSEvent* upEvent = sendFlagsChangedEvent
                          ? nil
@@ -5232,7 +5231,7 @@ bool TextInputHandlerBase::SetSelection(NSRange& aRange) {
     return false;
   }
   nsAutoString nativeChars;
-  nsCocoaUtils::GetStringForNSString([aNativeEvent characters], nativeChars);
+  CopyNSStringToXPCOMString([aNativeEvent characters], nativeChars);
 
   // this is not character inputting event, simply.
   if (nativeChars.IsEmpty() ||
@@ -5314,7 +5313,7 @@ void TextInputHandlerBase::KeyEventState::InitKeyEvent(
   if (!mInsertedString.IsEmpty()) {
     nsAutoString unhandledString;
     GetUnhandledString(unhandledString);
-    NSString* unhandledNSString = nsCocoaUtils::ToNSString(unhandledString);
+    NSString* unhandledNSString = XPCOMStringToNSString(unhandledString);
     // If the key event's some characters were already handled by
     // InsertString() calls, we need to create a dummy event which doesn't
     // include the handled characters.
@@ -5345,7 +5344,7 @@ void TextInputHandlerBase::KeyEventState::GetUnhandledString(
     return;
   }
   nsAutoString characters;
-  nsCocoaUtils::GetStringForNSString([mKeyEvent characters], characters);
+  CopyNSStringToXPCOMString([mKeyEvent characters], characters);
   if (characters.IsEmpty()) {
     return;
   }
@@ -5373,8 +5372,7 @@ TextInputHandlerBase::AutoInsertStringClearer::~AutoInsertStringClearer() {
     // If inserting string is a part of characters of the event,
     // we should record it as inserted string.
     nsAutoString characters;
-    nsCocoaUtils::GetStringForNSString([mState->mKeyEvent characters],
-                                       characters);
+    CopyNSStringToXPCOMString([mState->mKeyEvent characters], characters);
     nsAutoString insertedString(mState->mInsertedString);
     insertedString += *mState->mInsertString;
     if (StringBeginsWith(characters, insertedString)) {
diff --git a/widget/cocoa/VibrancyManager.h b/widget/cocoa/VibrancyManager.h
index d431540830..c70ec60a3b 100644
--- a/widget/cocoa/VibrancyManager.h
+++ b/widget/cocoa/VibrancyManager.h
@@ -24,6 +24,7 @@ namespace mozilla {
 enum class VibrancyType {
   TOOLTIP,
   MENU,
+  TITLEBAR,
 };
 
 /**
diff --git a/widget/cocoa/VibrancyManager.mm b/widget/cocoa/VibrancyManager.mm
index e9cfcc3be0..6062acb931 100644
--- a/widget/cocoa/VibrancyManager.mm
+++ b/widget/cocoa/VibrancyManager.mm
@@ -9,6 +9,7 @@
 #import <objc/message.h>
 
 #include "nsChildView.h"
+#include "mozilla/StaticPrefs_widget.h"
 
 using namespace mozilla;
 
@@ -30,18 +31,34 @@ static NSVisualEffectState VisualEffectStateForVibrancyType(
       // Tooltip and menu windows are never "key", so we need to tell the
       // vibrancy effect to look active regardless of window state.
       return NSVisualEffectStateActive;
-    default:
-      return NSVisualEffectStateFollowsWindowActiveState;
+    case VibrancyType::TITLEBAR:
+      break;
   }
+  return NSVisualEffectStateFollowsWindowActiveState;
 }
 
 static NSVisualEffectMaterial VisualEffectMaterialForVibrancyType(
-    VibrancyType aType, BOOL* aOutIsEmphasized) {
+    VibrancyType aType) {
   switch (aType) {
     case VibrancyType::TOOLTIP:
       return (NSVisualEffectMaterial)NSVisualEffectMaterialToolTip;
     case VibrancyType::MENU:
       return NSVisualEffectMaterialMenu;
+    case VibrancyType::TITLEBAR:
+      return NSVisualEffectMaterialTitlebar;
+  }
+}
+
+static NSVisualEffectBlendingMode VisualEffectBlendingModeForVibrancyType(
+    VibrancyType aType) {
+  switch (aType) {
+    case VibrancyType::TOOLTIP:
+    case VibrancyType::MENU:
+      return NSVisualEffectBlendingModeBehindWindow;
+    case VibrancyType::TITLEBAR:
+      return StaticPrefs::widget_macos_titlebar_blend_mode_behind_window()
+                 ? NSVisualEffectBlendingModeBehindWindow
+                 : NSVisualEffectBlendingModeWithinWindow;
   }
 }
 
@@ -53,11 +70,9 @@ static NSVisualEffectMaterial VisualEffectMaterialForVibrancyType(
 
   self.appearance = nil;
   self.state = VisualEffectStateForVibrancyType(mType);
-
-  BOOL isEmphasized = NO;
-  self.material = VisualEffectMaterialForVibrancyType(mType, &isEmphasized);
-  self.emphasized = isEmphasized;
-
+  self.material = VisualEffectMaterialForVibrancyType(mType);
+  self.blendingMode = VisualEffectBlendingModeForVibrancyType(mType);
+  self.emphasized = NO;
   return self;
 }
 
@@ -89,7 +104,7 @@ bool VibrancyManager::UpdateVibrantRegion(
   }
   auto& vr = *mVibrantRegions.GetOrInsertNew(uint32_t(aType));
   return vr.UpdateRegion(aRegion, mCoordinateConverter, mContainerView, ^() {
-    return this->CreateEffectView(aType);
+    return CreateEffectView(aType);
   });
 }
 
diff --git a/widget/cocoa/ViewRegion.mm b/widget/cocoa/ViewRegion.mm
index 62e76d2df8..5b275a18a3 100644
--- a/widget/cocoa/ViewRegion.mm
+++ b/widget/cocoa/ViewRegion.mm
@@ -12,8 +12,8 @@
 using namespace mozilla;
 
 ViewRegion::~ViewRegion() {
-  for (size_t i = 0; i < mViews.Length(); i++) {
-    [mViews[i] removeFromSuperview];
+  for (NSView* view : mViews) {
+    [view removeFromSuperview];
   }
 }
 
@@ -33,34 +33,31 @@ bool ViewRegion::UpdateRegion(const LayoutDeviceIntRegion& aRegion,
   nsTArray<NSView*> viewsToRecycle = std::move(mViews);
   // The mViews array is now empty.
 
-  size_t i = 0;
-  for (auto iter = aRegion.RectIter();
-       !iter.Done() || i < viewsToRecycle.Length(); i++) {
-    if (!iter.Done()) {
-      NSView* view = nil;
-      NSRect rect = aCoordinateConverter.DevPixelsToCocoaPoints(iter.Get());
-      if (i < viewsToRecycle.Length()) {
-        view = viewsToRecycle[i];
-      } else {
-        view = aViewCreationCallback();
-        [aContainerView addSubview:view];
-
-        // Now that the view is in the view hierarchy, it'll be kept alive by
-        // its superview, so we can drop our reference.
-        [view release];
-      }
-      if (!NSEqualRects(rect, [view frame])) {
-        [view setFrame:rect];
-      }
-      [view setNeedsDisplay:YES];
-      mViews.AppendElement(view);
-      iter.Next();
+  size_t viewsRecycled = 0;
+  for (auto iter = aRegion.RectIter(); !iter.Done(); iter.Next()) {
+    NSRect rect = aCoordinateConverter.DevPixelsToCocoaPoints(iter.Get());
+    NSView* view = nil;
+    if (viewsRecycled < viewsToRecycle.Length()) {
+      view = viewsToRecycle[viewsRecycled++];
     } else {
-      // Our new region is made of fewer rects than the old region, so we can
-      // remove this view. We only have a weak reference to it, so removing it
-      // from the view hierarchy will release it.
-      [viewsToRecycle[i] removeFromSuperview];
+      view = aViewCreationCallback();
+      [aContainerView addSubview:view];
+
+      // Now that the view is in the view hierarchy, it'll be kept alive by
+      // its superview, so we can drop our reference.
+      [view release];
     }
+    if (!NSEqualRects(rect, view.frame)) {
+      view.frame = rect;
+    }
+    view.needsDisplay = YES;
+    mViews.AppendElement(view);
+  }
+  for (NSView* view : Span(viewsToRecycle).From(viewsRecycled)) {
+    // Our new region is made of fewer rects than the old region, so we can
+    // remove this view. We only have a weak reference to it, so removing it
+    // from the view hierarchy will release it.
+    [view removeFromSuperview];
   }
 
   mRegion = aRegion;
diff --git a/widget/cocoa/moz.build b/widget/cocoa/moz.build
index ddb402e2cc..d0939d34c7 100644
--- a/widget/cocoa/moz.build
+++ b/widget/cocoa/moz.build
@@ -11,12 +11,6 @@ with Files("**"):
 with Files("*TextInput*"):
     BUG_COMPONENT = ("Core", "DOM: UI Events & Focus Handling")
 
-XPIDL_SOURCES += [
-    "nsPIWidgetCocoa.idl",
-]
-
-XPIDL_MODULE = "widget_cocoa"
-
 EXPORTS += [
     "DesktopBackgroundImage.h",
     "MediaHardwareKeysEventSourceMac.h",
diff --git a/widget/cocoa/nsChildView.mm b/widget/cocoa/nsChildView.mm
index 79919ba69a..d3241a983f 100644
--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -473,17 +473,20 @@ void* nsChildView::GetNativeData(uint32_t aDataType) {
 #pragma mark -
 
 void nsChildView::SuppressAnimation(bool aSuppress) {
-  GetAppWindowWidget()->SuppressAnimation(aSuppress);
+  if (nsCocoaWindow* widget = GetAppWindowWidget()) {
+    widget->SuppressAnimation(aSuppress);
+  }
 }
 
 bool nsChildView::IsVisible() const {
   NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
 
   if (!mVisible) {
-    return mVisible;
+    return false;
   }
 
-  if (!GetAppWindowWidget()->IsVisible()) {
+  nsCocoaWindow* widget = GetAppWindowWidget();
+  if (NS_WARN_IF(!widget) || !widget->IsVisible()) {
     return false;
   }
 
@@ -739,11 +742,11 @@ void nsChildView::Resize(double aWidth, double aHeight, bool aRepaint) {
   mBounds.height = height;
 
   ManipulateViewWithoutNeedingDisplay(mView, ^{
-    [mView setFrame:DevPixelsToCocoaPoints(mBounds)];
+    mView.frame = DevPixelsToCocoaPoints(mBounds);
   });
 
   if (mVisible && aRepaint) {
-    [[mView pixelHostingView] setNeedsDisplay:YES];
+    mView.pixelHostingView.needsDisplay = YES;
   }
 
   ReportSizeEvent();
@@ -779,11 +782,11 @@ void nsChildView::Resize(double aX, double aY, double aWidth, double aHeight,
   }
 
   ManipulateViewWithoutNeedingDisplay(mView, ^{
-    [mView setFrame:DevPixelsToCocoaPoints(mBounds)];
+    mView.frame = DevPixelsToCocoaPoints(mBounds);
   });
 
   if (mVisible && aRepaint) {
-    [[mView pixelHostingView] setNeedsDisplay:YES];
+    mView.pixelHostingView.needsDisplay = YES;
   }
 
   if (isMoving) {
@@ -1070,10 +1073,8 @@ nsresult nsChildView::SynthesizeNativeTouchpadDoubleTap(
 
 bool nsChildView::SendEventToNativeMenuSystem(NSEvent* aEvent) {
   bool handled = false;
-  nsCocoaWindow* widget = GetAppWindowWidget();
-  if (widget) {
-    nsMenuBarX* mb = widget->GetMenuBar();
-    if (mb) {
+  if (nsCocoaWindow* widget = GetAppWindowWidget()) {
+    if (nsMenuBarX* mb = widget->GetMenuBar()) {
       // Check if main menu wants to handle the event.
       handled = mb->PerformKeyEquivalent(aEvent);
     }
@@ -1157,10 +1158,8 @@ nsresult nsChildView::ActivateNativeMenuItemAt(const nsAString& indexString) {
 nsresult nsChildView::ForceUpdateNativeMenuAt(const nsAString& indexString) {
   NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
 
-  nsCocoaWindow* widget = GetAppWindowWidget();
-  if (widget) {
-    nsMenuBarX* mb = widget->GetMenuBar();
-    if (mb) {
+  if (nsCocoaWindow* widget = GetAppWindowWidget()) {
+    if (nsMenuBarX* mb = widget->GetMenuBar()) {
       if (indexString.IsEmpty())
         mb->ForceNativeMenuReload();
       else
@@ -1689,33 +1688,6 @@ RefPtr<layers::NativeLayerRoot> nsChildView::GetNativeLayerRoot() {
   return mNativeLayerRoot;
 }
 
-static int32_t FindTitlebarBottom(
-    const nsTArray<nsIWidget::ThemeGeometry>& aThemeGeometries,
-    int32_t aWindowWidth) {
-  int32_t titlebarBottom = 0;
-  for (auto& g : aThemeGeometries) {
-    if (g.mType == eThemeGeometryTypeTitlebar && g.mRect.X() <= 0 &&
-        g.mRect.XMost() >= aWindowWidth && g.mRect.Y() <= 0) {
-      titlebarBottom = std::max(titlebarBottom, g.mRect.YMost());
-    }
-  }
-  return titlebarBottom;
-}
-
-static int32_t FindUnifiedToolbarBottom(
-    const nsTArray<nsIWidget::ThemeGeometry>& aThemeGeometries,
-    int32_t aWindowWidth, int32_t aTitlebarBottom) {
-  int32_t unifiedToolbarBottom = aTitlebarBottom;
-  for (uint32_t i = 0; i < aThemeGeometries.Length(); ++i) {
-    const nsIWidget::ThemeGeometry& g = aThemeGeometries[i];
-    if ((g.mType == eThemeGeometryTypeToolbar) && g.mRect.X() <= 0 &&
-        g.mRect.XMost() >= aWindowWidth && g.mRect.Y() <= aTitlebarBottom) {
-      unifiedToolbarBottom = std::max(unifiedToolbarBottom, g.mRect.YMost());
-    }
-  }
-  return unifiedToolbarBottom;
-}
-
 static LayoutDeviceIntRect FindFirstRectOfType(
     const nsTArray<nsIWidget::ThemeGeometry>& aThemeGeometries,
     nsITheme::ThemeGeometryType aThemeGeometryType) {
@@ -1730,32 +1702,17 @@ static LayoutDeviceIntRect FindFirstRectOfType(
 
 void nsChildView::UpdateThemeGeometries(
     const nsTArray<ThemeGeometry>& aThemeGeometries) {
-  if (![mView window]) return;
+  if (!mView.window) {
+    return;
+  }
 
   UpdateVibrancy(aThemeGeometries);
 
-  if (![[mView window] isKindOfClass:[ToolbarWindow class]]) return;
-
-  // Update unified toolbar height and sheet attachment position.
-  int32_t windowWidth = mBounds.width;
-  int32_t titlebarBottom = FindTitlebarBottom(aThemeGeometries, windowWidth);
-  int32_t unifiedToolbarBottom =
-      FindUnifiedToolbarBottom(aThemeGeometries, windowWidth, titlebarBottom);
-  int32_t toolboxBottom =
-      FindFirstRectOfType(aThemeGeometries, eThemeGeometryTypeToolbox).YMost();
+  if (![mView.window isKindOfClass:[ToolbarWindow class]]) {
+    return;
+  }
 
   ToolbarWindow* win = (ToolbarWindow*)[mView window];
-  int32_t titlebarHeight = [win drawsContentsIntoWindowFrame]
-                               ? 0
-                               : CocoaPointsToDevPixels([win titlebarHeight]);
-  int32_t devUnifiedHeight = titlebarHeight + unifiedToolbarBottom;
-  [win setUnifiedToolbarHeight:DevPixelsToCocoaPoints(devUnifiedHeight)];
-
-  int32_t sheetPositionDevPx = std::max(toolboxBottom, unifiedToolbarBottom);
-  NSPoint sheetPositionView = {0, DevPixelsToCocoaPoints(sheetPositionDevPx)};
-  NSPoint sheetPositionWindow = [mView convertPoint:sheetPositionView
-                                             toView:nil];
-  [win setSheetAttachmentPosition:sheetPositionWindow.y];
 
   // Update titlebar control offsets.
   LayoutDeviceIntRect windowButtonRect =
@@ -1768,10 +1725,8 @@ void nsChildView::UpdateThemeGeometries(
 static Maybe<VibrancyType> ThemeGeometryTypeToVibrancyType(
     nsITheme::ThemeGeometryType aThemeGeometryType) {
   switch (aThemeGeometryType) {
-    case eThemeGeometryTypeTooltip:
-      return Some(VibrancyType::TOOLTIP);
-    case eThemeGeometryTypeMenu:
-      return Some(VibrancyType::MENU);
+    case eThemeGeometryTypeTitlebar:
+      return Some(VibrancyType::TITLEBAR);
     default:
       return Nothing();
   }
@@ -1781,7 +1736,7 @@ static LayoutDeviceIntRegion GatherVibrantRegion(
     const nsTArray<nsIWidget::ThemeGeometry>& aThemeGeometries,
     VibrancyType aVibrancyType) {
   LayoutDeviceIntRegion region;
-  for (auto& geometry : aThemeGeometries) {
+  for (const auto& geometry : aThemeGeometries) {
     if (ThemeGeometryTypeToVibrancyType(geometry.mType) ==
         Some(aVibrancyType)) {
       region.OrWith(geometry.mRect);
@@ -1790,40 +1745,13 @@ static LayoutDeviceIntRegion GatherVibrantRegion(
   return region;
 }
 
-template <typename Region>
-static void MakeRegionsNonOverlappingImpl(Region& aOutUnion) {}
-
-template <typename Region, typename... Regions>
-static void MakeRegionsNonOverlappingImpl(Region& aOutUnion, Region& aFirst,
-                                          Regions&... aRest) {
-  MakeRegionsNonOverlappingImpl(aOutUnion, aRest...);
-  aFirst.SubOut(aOutUnion);
-  aOutUnion.OrWith(aFirst);
-}
-
-// Subtracts parts from regions in such a way that they don't have any overlap.
-// Each region in the argument list will have the union of all the regions
-// *following* it subtracted from itself. In other words, the arguments are
-// sorted low priority to high priority.
-template <typename Region, typename... Regions>
-static void MakeRegionsNonOverlapping(Region& aFirst, Regions&... aRest) {
-  Region unionOfAll;
-  MakeRegionsNonOverlappingImpl(unionOfAll, aFirst, aRest...);
-}
-
 void nsChildView::UpdateVibrancy(
     const nsTArray<ThemeGeometry>& aThemeGeometries) {
-  LayoutDeviceIntRegion menuRegion =
-      GatherVibrantRegion(aThemeGeometries, VibrancyType::MENU);
-  LayoutDeviceIntRegion tooltipRegion =
-      GatherVibrantRegion(aThemeGeometries, VibrancyType::TOOLTIP);
-
-  MakeRegionsNonOverlapping(menuRegion, tooltipRegion);
+  LayoutDeviceIntRegion titlebarRegion =
+      GatherVibrantRegion(aThemeGeometries, VibrancyType::TITLEBAR);
 
   auto& vm = EnsureVibrancyManager();
-  bool changed = false;
-  changed |= vm.UpdateVibrantRegion(VibrancyType::MENU, menuRegion);
-  changed |= vm.UpdateVibrantRegion(VibrancyType::TOOLTIP, tooltipRegion);
+  bool changed = vm.UpdateVibrantRegion(VibrancyType::TITLEBAR, titlebarRegion);
 
   if (changed) {
     SuspendAsyncCATransactions();
@@ -1834,7 +1762,7 @@ mozilla::VibrancyManager& nsChildView::EnsureVibrancyManager() {
   MOZ_ASSERT(mView, "Only call this once we have a view!");
   if (!mVibrancyManager) {
     mVibrancyManager =
-        MakeUnique<VibrancyManager>(*this, [mView vibrancyViewsContainer]);
+        MakeUnique<VibrancyManager>(*this, mView.vibrancyViewsContainer);
   }
   return *mVibrancyManager;
 }
@@ -1897,7 +1825,7 @@ void nsChildView::UpdateWindowDraggingRegion(
   // Suppress calls to setNeedsDisplay during NSView geometry changes.
   ManipulateViewWithoutNeedingDisplay(mView, ^() {
     changed = mNonDraggableRegion.UpdateRegion(
-        nonDraggable, *this, [mView nonDraggableViewsContainer], ^() {
+        nonDraggable, *this, mView.nonDraggableViewsContainer, ^() {
           return [[NonDraggableView alloc] initWithFrame:NSZeroRect];
         });
   });
@@ -2198,22 +2126,22 @@ NSEvent* gLastDragMouseDownEvent = nil;  // [strong]
     mCancelSwipeAnimation = nil;
 #endif
 
+    auto bounds = self.bounds;
     mNonDraggableViewsContainer =
-        [[ViewRegionContainerView alloc] initWithFrame:[self bounds]];
+        [[ViewRegionContainerView alloc] initWithFrame:bounds];
     mVibrancyViewsContainer =
-        [[ViewRegionContainerView alloc] initWithFrame:[self bounds]];
+        [[ViewRegionContainerView alloc] initWithFrame:bounds];
 
-    [mNonDraggableViewsContainer
-        setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
-    [mVibrancyViewsContainer
-        setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
+    mNonDraggableViewsContainer.autoresizingMask =
+        mVibrancyViewsContainer.autoresizingMask =
+            NSViewWidthSizable | NSViewHeightSizable;
 
     [self addSubview:mNonDraggableViewsContainer];
     [self addSubview:mVibrancyViewsContainer];
 
-    mPixelHostingView = [[PixelHostingView alloc] initWithFrame:[self bounds]];
-    [mPixelHostingView
-        setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
+    mPixelHostingView = [[PixelHostingView alloc] initWithFrame:bounds];
+    mPixelHostingView.autoresizingMask =
+        NSViewWidthSizable | NSViewHeightSizable;
 
     [self addSubview:mPixelHostingView];
 
@@ -2222,7 +2150,7 @@ NSEvent* gLastDragMouseDownEvent = nil;  // [strong]
     mRootCALayer.bounds = NSZeroRect;
     mRootCALayer.anchorPoint = NSZeroPoint;
     mRootCALayer.contentsGravity = kCAGravityTopLeft;
-    [[mPixelHostingView layer] addSublayer:mRootCALayer];
+    [mPixelHostingView.layer addSublayer:mRootCALayer];
 
     mLastPressureStage = 0;
   }
@@ -2398,7 +2326,7 @@ NSEvent* gLastDragMouseDownEvent = nil;  // [strong]
     // This call will cause updateRootCALayer to be called during the upcoming
     // main thread CoreAnimation transaction. It will also trigger a transaction
     // if no transaction is currently pending.
-    [[mPixelHostingView layer] setNeedsDisplay];
+    [mPixelHostingView.layer setNeedsDisplay];
   }
 }
 
@@ -5129,18 +5057,12 @@ BOOL ChildViewMouseTracker::WindowAcceptsEvent(NSWindow* aWindow,
 
     case WindowType::TopLevel:
     case WindowType::Dialog:
-      if ([aWindow attachedSheet]) return NO;
+      if (aWindow.attachedSheet) {
+        return NO;
+      }
 
       topLevelWindow = aWindow;
       break;
-    case WindowType::Sheet: {
-      nsIWidget* parentWidget = windowWidget->GetSheetWindowParent();
-      if (!parentWidget) return YES;
-
-      topLevelWindow = (NSWindow*)parentWidget->GetNativeData(NS_NATIVE_WINDOW);
-      break;
-    }
-
     default:
       return YES;
   }
diff --git a/widget/cocoa/nsCocoaWindow.h b/widget/cocoa/nsCocoaWindow.h
index 621c32eb44..96e117ba26 100644
--- a/widget/cocoa/nsCocoaWindow.h
+++ b/widget/cocoa/nsCocoaWindow.h
@@ -12,7 +12,6 @@
 
 #include "mozilla/RefPtr.h"
 #include "nsBaseWidget.h"
-#include "nsPIWidgetCocoa.h"
 #include "nsCocoaUtils.h"
 #include "nsTouchBar.h"
 #include <dlfcn.h>
@@ -27,12 +26,6 @@ namespace mozilla {
 enum class NativeKeyBindingsType : uint8_t;
 }  // namespace mozilla
 
-typedef struct _nsCocoaWindowList {
-  _nsCocoaWindowList() : prev(nullptr), window(nullptr) {}
-  struct _nsCocoaWindowList* prev;
-  nsCocoaWindow* window;  // Weak
-} nsCocoaWindowList;
-
 // NSWindow subclass that is the base class for all of our own window classes.
 // Among other things, this class handles the storage of those settings that
 // need to be persisted across window destruction and reconstruction, i.e. when
@@ -169,102 +162,75 @@ typedef struct _nsCocoaWindowList {
 - (void)sendToplevelDeactivateEvents;
 @end
 
-@interface MOZTitlebarView : NSVisualEffectView
-@end
-
 @interface FullscreenTitlebarTracker : NSTitlebarAccessoryViewController
 - (FullscreenTitlebarTracker*)init;
 @end
 
 // NSWindow subclass for handling windows with toolbars.
 @interface ToolbarWindow : BaseWindow {
-  // This window's titlebar view, if present.
-  // Will be nil if the window has neither a titlebar nor a unified toolbar.
-  // This view is a subview of the window's content view and gets created and
-  // destroyed by updateTitlebarView.
-  MOZTitlebarView* mTitlebarView;  // [STRONG]
   // mFullscreenTitlebarTracker attaches an invisible rectangle to the system
   // title bar. This allows us to detect when the title bar is showing in
   // fullscreen.
   FullscreenTitlebarTracker* mFullscreenTitlebarTracker;
 
-  CGFloat mUnifiedToolbarHeight;
-  CGFloat mSheetAttachmentPosition;
   CGFloat mMenuBarHeight;
-  /* Store the height of the titlebar when this window is initialized. The
-     titlebarHeight getter returns 0 when in fullscreen, which is not useful in
-     some cases. */
-  CGFloat mInitialTitlebarHeight;
   NSRect mWindowButtonsRect;
 }
-- (void)setUnifiedToolbarHeight:(CGFloat)aHeight;
-- (CGFloat)unifiedToolbarHeight;
-- (CGFloat)titlebarHeight;
-- (NSRect)titlebarRect;
-- (void)setTitlebarNeedsDisplay;
 - (void)setDrawsContentsIntoWindowFrame:(BOOL)aState;
-- (void)setSheetAttachmentPosition:(CGFloat)aY;
-- (CGFloat)sheetAttachmentPosition;
 - (void)placeWindowButtons:(NSRect)aRect;
 - (NSRect)windowButtonsRect;
 - (void)windowMainStateChanged;
 @end
 
-class nsCocoaWindow final : public nsBaseWidget, public nsPIWidgetCocoa {
+class nsCocoaWindow final : public nsBaseWidget {
  private:
   typedef nsBaseWidget Inherited;
 
  public:
   nsCocoaWindow();
 
-  NS_DECL_ISUPPORTS_INHERITED
-  NS_DECL_NSPIWIDGETCOCOA;  // semicolon for clang-format bug 1629756
-
-  [[nodiscard]] virtual nsresult Create(nsIWidget* aParent,
-                                        nsNativeWidget aNativeParent,
-                                        const DesktopIntRect& aRect,
-                                        InitData* = nullptr) override;
-
-  [[nodiscard]] virtual nsresult Create(nsIWidget* aParent,
-                                        nsNativeWidget aNativeParent,
-                                        const LayoutDeviceIntRect& aRect,
-                                        InitData* = nullptr) override;
-
-  virtual void Destroy() override;
-
-  virtual void Show(bool aState) override;
-  virtual bool NeedsRecreateToReshow() override;
-
-  virtual nsIWidget* GetSheetWindowParent(void) override;
-  virtual void Enable(bool aState) override;
-  virtual bool IsEnabled() const override;
-  virtual void SetModal(bool aState) override;
-  virtual void SetFakeModal(bool aState) override;
-  virtual bool IsRunningAppModal() override;
-  virtual bool IsVisible() const override;
-  virtual void SetFocus(Raise, mozilla::dom::CallerType aCallerType) override;
-  virtual LayoutDeviceIntPoint WidgetToScreenOffset() override;
-  virtual LayoutDeviceIntPoint GetClientOffset() override;
-  virtual LayoutDeviceIntMargin ClientToWindowMargin() override;
-
-  virtual void* GetNativeData(uint32_t aDataType) override;
-
-  virtual void ConstrainPosition(DesktopIntPoint&) override;
-  virtual void SetSizeConstraints(const SizeConstraints& aConstraints) override;
-  virtual void Move(double aX, double aY) override;
-  virtual nsSizeMode SizeMode() override { return mSizeMode; }
-  virtual void SetSizeMode(nsSizeMode aMode) override;
-  virtual void GetWorkspaceID(nsAString& workspaceID) override;
-  virtual void MoveToWorkspace(const nsAString& workspaceID) override;
-  virtual void SuppressAnimation(bool aSuppress) override;
-  virtual void HideWindowChrome(bool aShouldHide) override;
-
-  virtual bool PrepareForFullscreenTransition(nsISupports** aData) override;
-  virtual void PerformFullscreenTransition(FullscreenTransitionStage aStage,
-                                           uint16_t aDuration,
-                                           nsISupports* aData,
-                                           nsIRunnable* aCallback) override;
-  virtual void CleanupFullscreenTransition() override;
+  [[nodiscard]] nsresult Create(nsIWidget* aParent,
+                                nsNativeWidget aNativeParent,
+                                const DesktopIntRect& aRect,
+                                InitData* = nullptr) override;
+
+  [[nodiscard]] nsresult Create(nsIWidget* aParent,
+                                nsNativeWidget aNativeParent,
+                                const LayoutDeviceIntRect& aRect,
+                                InitData* = nullptr) override;
+
+  void Destroy() override;
+
+  void Show(bool aState) override;
+  bool NeedsRecreateToReshow() override;
+
+  void Enable(bool aState) override;
+  bool IsEnabled() const override;
+  void SetModal(bool aState) override;
+  bool IsRunningAppModal() override;
+  bool IsVisible() const override;
+  void SetFocus(Raise, mozilla::dom::CallerType aCallerType) override;
+  LayoutDeviceIntPoint WidgetToScreenOffset() override;
+  LayoutDeviceIntPoint GetClientOffset() override;
+  LayoutDeviceIntMargin ClientToWindowMargin() override;
+
+  void* GetNativeData(uint32_t aDataType) override;
+
+  void ConstrainPosition(DesktopIntPoint&) override;
+  void SetSizeConstraints(const SizeConstraints& aConstraints) override;
+  void Move(double aX, double aY) override;
+  nsSizeMode SizeMode() override { return mSizeMode; }
+  void SetSizeMode(nsSizeMode aMode) override;
+  void GetWorkspaceID(nsAString& workspaceID) override;
+  void MoveToWorkspace(const nsAString& workspaceID) override;
+  void SuppressAnimation(bool aSuppress) override;
+  void HideWindowChrome(bool aShouldHide) override;
+
+  bool PrepareForFullscreenTransition(nsISupports** aData) override;
+  void PerformFullscreenTransition(FullscreenTransitionStage aStage,
+                                   uint16_t aDuration, nsISupports* aData,
+                                   nsIRunnable* aCallback) override;
+  void CleanupFullscreenTransition() override;
   nsresult MakeFullScreen(bool aFullScreen) final;
   nsresult MakeFullScreenWithNativeTransition(bool aFullScreen) final;
   NSAnimation* FullscreenTransitionAnimation() const {
@@ -277,79 +243,79 @@ class nsCocoaWindow final : public nsBaseWidget, public nsPIWidgetCocoa {
     mFullscreenTransitionAnimation = nil;
   }
 
-  virtual void Resize(double aWidth, double aHeight, bool aRepaint) override;
-  virtual void Resize(double aX, double aY, double aWidth, double aHeight,
-                      bool aRepaint) override;
+  void Resize(double aWidth, double aHeight, bool aRepaint) override;
+  void Resize(double aX, double aY, double aWidth, double aHeight,
+              bool aRepaint) override;
   NSRect GetClientCocoaRect();
-  virtual LayoutDeviceIntRect GetClientBounds() override;
-  virtual LayoutDeviceIntRect GetScreenBounds() override;
+  LayoutDeviceIntRect GetClientBounds() override;
+  LayoutDeviceIntRect GetScreenBounds() override;
   void ReportMoveEvent();
   void ReportSizeEvent();
-  virtual void SetCursor(const Cursor&) override;
+  void SetCursor(const Cursor&) override;
 
   CGFloat BackingScaleFactor();
   void BackingScaleFactorChanged();
-  virtual double GetDefaultScaleInternal() override;
-  virtual int32_t RoundsWidgetCoordinatesTo() override;
+  double GetDefaultScaleInternal() override;
+  int32_t RoundsWidgetCoordinatesTo() override;
 
   mozilla::DesktopToLayoutDeviceScale GetDesktopToDeviceScale() final {
     return mozilla::DesktopToLayoutDeviceScale(BackingScaleFactor());
   }
 
-  virtual nsresult SetTitle(const nsAString& aTitle) override;
-
-  virtual void Invalidate(const LayoutDeviceIntRect& aRect) override;
-  virtual WindowRenderer* GetWindowRenderer() override;
-  virtual nsresult DispatchEvent(mozilla::WidgetGUIEvent* aEvent,
-                                 nsEventStatus& aStatus) override;
-  virtual void CaptureRollupEvents(bool aDoCapture) override;
-  [[nodiscard]] virtual nsresult GetAttention(int32_t aCycleCount) override;
-  virtual bool HasPendingInputEvent() override;
-  virtual TransparencyMode GetTransparencyMode() override;
-  virtual void SetTransparencyMode(TransparencyMode aMode) override;
-  virtual void SetWindowShadowStyle(mozilla::WindowShadow aStyle) override;
-  virtual void SetWindowOpacity(float aOpacity) override;
-  virtual void SetWindowTransform(
-      const mozilla::gfx::Matrix& aTransform) override;
-  virtual void SetInputRegion(const InputRegion&) override;
-  virtual void SetColorScheme(
-      const mozilla::Maybe<mozilla::ColorScheme>&) override;
-  virtual void SetShowsToolbarButton(bool aShow) override;
-  virtual void SetSupportsNativeFullscreen(bool aShow) override;
-  virtual void SetWindowAnimationType(WindowAnimationType aType) override;
-  virtual void SetDrawsTitle(bool aDrawTitle) override;
-  virtual nsresult SetNonClientMargins(const LayoutDeviceIntMargin&) override;
+  nsresult SetTitle(const nsAString& aTitle) override;
+
+  void Invalidate(const LayoutDeviceIntRect& aRect) override;
+  WindowRenderer* GetWindowRenderer() override;
+  nsresult DispatchEvent(mozilla::WidgetGUIEvent* aEvent,
+                         nsEventStatus& aStatus) override;
+  void CaptureRollupEvents(bool aDoCapture) override;
+  [[nodiscard]] nsresult GetAttention(int32_t aCycleCount) override;
+  bool HasPendingInputEvent() override;
+  TransparencyMode GetTransparencyMode() override;
+  void SetTransparencyMode(TransparencyMode aMode) override;
+  void SetWindowShadowStyle(mozilla::WindowShadow aStyle) override;
+  void SetWindowOpacity(float aOpacity) override;
+  void SetWindowTransform(const mozilla::gfx::Matrix& aTransform) override;
+  void SetInputRegion(const InputRegion&) override;
+  void SetColorScheme(const mozilla::Maybe<mozilla::ColorScheme>&) override;
+  void SetShowsToolbarButton(bool aShow) override;
+  void SetSupportsNativeFullscreen(bool aShow) override;
+  void SetWindowAnimationType(WindowAnimationType aType) override;
+  void SetDrawsTitle(bool aDrawTitle) override;
+  nsresult SetNonClientMargins(const LayoutDeviceIntMargin&) override;
   void SetDrawsInTitlebar(bool aState);
-  virtual void UpdateThemeGeometries(
+  void UpdateThemeGeometries(
       const nsTArray<ThemeGeometry>& aThemeGeometries) override;
-  virtual nsresult SynthesizeNativeMouseEvent(
-      LayoutDeviceIntPoint aPoint, NativeMouseMessage aNativeMessage,
-      mozilla::MouseButton aButton, nsIWidget::Modifiers aModifierFlags,
-      nsIObserver* aObserver) override;
-  virtual nsresult SynthesizeNativeMouseScrollEvent(
+  nsresult SynthesizeNativeMouseEvent(LayoutDeviceIntPoint aPoint,
+                                      NativeMouseMessage aNativeMessage,
+                                      mozilla::MouseButton aButton,
+                                      nsIWidget::Modifiers aModifierFlags,
+                                      nsIObserver* aObserver) override;
+  nsresult SynthesizeNativeMouseScrollEvent(
       LayoutDeviceIntPoint aPoint, uint32_t aNativeMessage, double aDeltaX,
       double aDeltaY, double aDeltaZ, uint32_t aModifierFlags,
       uint32_t aAdditionalFlags, nsIObserver* aObserver) override;
-  virtual void LockAspectRatio(bool aShouldLock) override;
+  void LockAspectRatio(bool aShouldLock) override;
 
   void DispatchSizeModeEvent();
   void DispatchOcclusionEvent();
 
   // be notified that a some form of drag event needs to go into Gecko
-  virtual bool DragEvent(unsigned int aMessage,
-                         mozilla::gfx::Point aMouseGlobal,
-                         UInt16 aKeyModifiers);
+  bool DragEvent(unsigned int aMessage, mozilla::gfx::Point aMouseGlobal,
+                 UInt16 aKeyModifiers);
+
+  bool HasModalDescendants() const { return mNumModalDescendants > 0; }
+  bool IsModal() const { return mModal; }
 
-  bool HasModalDescendents() { return mNumModalDescendents > 0; }
   NSWindow* GetCocoaWindow() { return mWindow; }
 
   void SetMenuBar(RefPtr<nsMenuBarX>&& aMenuBar);
   nsMenuBarX* GetMenuBar();
 
-  virtual void SetInputContext(const InputContext& aContext,
-                               const InputContextAction& aAction) override;
-  virtual InputContext GetInputContext() override { return mInputContext; }
-  MOZ_CAN_RUN_SCRIPT virtual bool GetEditCommands(
+  void SetInputContext(const InputContext& aContext,
+                       const InputContextAction& aAction) override;
+  InputContext GetInputContext() override { return mInputContext; }
+  MOZ_CAN_RUN_SCRIPT bool GetEditCommands(
       mozilla::NativeKeyBindingsType aType,
       const mozilla::WidgetKeyboardEvent& aEvent,
       nsTArray<mozilla::CommandInt>& aCommands) override;
@@ -400,6 +366,7 @@ class nsCocoaWindow final : public nsBaseWidget, public nsPIWidgetCocoa {
   void DestroyNativeWindow();
   void UpdateBounds();
   int32_t GetWorkspaceID();
+  void SendSetZLevelEvent();
 
   void DoResize(double aX, double aY, double aWidth, double aHeight,
                 bool aRepaint, bool aConstrainToCurrentScreen);
@@ -407,7 +374,7 @@ class nsCocoaWindow final : public nsBaseWidget, public nsPIWidgetCocoa {
   void UpdateFullscreenState(bool aFullScreen, bool aNativeMode);
   nsresult DoMakeFullScreen(bool aFullScreen, bool aUseSystemTransition);
 
-  virtual already_AddRefed<nsIWidget> AllocateChildPopupWidget() override {
+  already_AddRefed<nsIWidget> AllocateChildPopupWidget() override {
     return nsIWidget::CreateTopLevelWindow();
   }
 
@@ -417,8 +384,6 @@ class nsCocoaWindow final : public nsBaseWidget, public nsPIWidgetCocoa {
   WindowDelegate*
       mDelegate;  // our delegate for processing window msgs [STRONG]
   RefPtr<nsMenuBarX> mMenuBar;
-  NSWindow* mSheetWindowParent;  // if this is a sheet, this is the NSWindow
-                                 // it's attached to
   nsChildView*
       mPopupContentView;  // if this is a popup, this is its content widget
   // if this is a toplevel window, and there is any ongoing fullscreen
@@ -432,8 +397,6 @@ class nsCocoaWindow final : public nsBaseWidget, public nsPIWidgetCocoa {
   WindowAnimationType mAnimationType;
 
   bool mWindowMadeHere;  // true if we created the window, false for embedding
-  bool mSheetNeedsShow;  // if this is a sheet, are we waiting to be shown?
-                         // this is used for sibling sheet contention only
   nsSizeMode mSizeMode;
   bool mInFullScreenMode;
   // Whether we are currently using native fullscreen. It could be false because
@@ -482,19 +445,18 @@ class nsCocoaWindow final : public nsBaseWidget, public nsPIWidgetCocoa {
   // unnecessary OcclusionStateChanged events.
   bool mHasStartedNativeFullscreen;
 
-  bool mModal;
-  bool mFakeModal;
-
-  bool mIsAnimationSuppressed;
+  bool mModal = false;
+  bool mIsAnimationSuppressed = false;
 
-  bool mInReportMoveEvent;  // true if in a call to ReportMoveEvent().
-  bool mInResize;           // true if in a call to DoResize().
-  bool mWindowTransformIsIdentity;
-  bool mAlwaysOnTop;
-  bool mAspectRatioLocked;
+  bool mInReportMoveEvent = false;  // true if in a call to ReportMoveEvent().
+  bool mInResize = false;           // true if in a call to DoResize().
+  bool mWindowTransformIsIdentity = true;
+  bool mAlwaysOnTop = false;
+  bool mAspectRatioLocked = false;
   bool mIsAlert = false;  // True if this is an non-native alert window.
+  bool mWasShown = false;
 
-  int32_t mNumModalDescendents;
+  int32_t mNumModalDescendants = 0;
   InputContext mInputContext;
   NSWindowAnimationBehavior mWindowAnimationBehavior;
 
@@ -508,9 +470,6 @@ class nsCocoaWindow final : public nsBaseWidget, public nsPIWidgetCocoa {
   // to EndOurNativeTransition() when the native transition is complete.
   bool CanStartNativeTransition();
   void EndOurNativeTransition();
-
-  // true if Show() has been called.
-  bool mWasShown;
 };
 
 #endif  // nsCocoaWindow_h_
diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
index 4b135e7565..8e54d9e7fd 100644
--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -66,15 +66,6 @@ using namespace mozilla::layers;
 using namespace mozilla::widget;
 using namespace mozilla;
 
-int32_t gXULModalLevel = 0;
-
-// In principle there should be only one app-modal window at any given time.
-// But sometimes, despite our best efforts, another window appears above the
-// current app-modal window.  So we need to keep a linked list of app-modal
-// windows.  (A non-sheet window that appears above an app-modal window is
-// also made app-modal.)  See nsCocoaWindow::SetModal().
-nsCocoaWindowList* gGeckoAppModalWindowList = NULL;
-
 BOOL sTouchBarIsInitialized = NO;
 
 // defined in nsMenuBarX.mm
@@ -83,6 +74,8 @@ extern NSMenu* sApplicationMenu;  // Application menu shared by all menubars
 // defined in nsChildView.mm
 extern BOOL gSomeMenuBarPainted;
 
+static uint32_t sModalWindowCount = 0;
+
 extern "C" {
 // CGSPrivate.h
 typedef NSInteger CGSConnection;
@@ -105,13 +98,6 @@ extern CGError CGSSetWindowTransform(CGSConnection cid, CGSWindow wid,
 
 #define NS_APPSHELLSERVICE_CONTRACTID "@mozilla.org/appshell/appShellService;1"
 
-NS_IMPL_ISUPPORTS_INHERITED(nsCocoaWindow, Inherited, nsPIWidgetCocoa)
-
-// A note on testing to see if your object is a sheet...
-// |mWindowType == WindowType::Sheet| is true if your gecko nsIWidget is a sheet
-// widget - whether or not the sheet is showing. |[mWindow isSheet]| will return
-// true *only when the sheet is actually showing*. Choose your test wisely.
-
 static void RollUpPopups(nsIRollupListener::AllowAnimations aAllowAnimations =
                              nsIRollupListener::AllowAnimations::Yes) {
   if (RefPtr pm = nsXULPopupManager::GetInstance()) {
@@ -139,33 +125,21 @@ nsCocoaWindow::nsCocoaWindow()
       mAncestorLink(nullptr),
       mWindow(nil),
       mDelegate(nil),
-      mSheetWindowParent(nil),
       mPopupContentView(nil),
       mFullscreenTransitionAnimation(nil),
       mShadowStyle(WindowShadow::None),
       mBackingScaleFactor(0.0),
       mAnimationType(nsIWidget::eGenericWindowAnimation),
       mWindowMadeHere(false),
-      mSheetNeedsShow(false),
       mSizeMode(nsSizeMode_Normal),
       mInFullScreenMode(false),
       mInNativeFullScreenMode(false),
       mIgnoreOcclusionCount(0),
       mHasStartedNativeFullscreen(false),
-      mModal(false),
-      mFakeModal(false),
-      mIsAnimationSuppressed(false),
-      mInReportMoveEvent(false),
-      mInResize(false),
-      mWindowTransformIsIdentity(true),
-      mAlwaysOnTop(false),
-      mAspectRatioLocked(false),
-      mNumModalDescendents(0),
-      mWindowAnimationBehavior(NSWindowAnimationBehaviorDefault),
-      mWasShown(false) {
+      mWindowAnimationBehavior(NSWindowAnimationBehaviorDefault) {
   // Disable automatic tabbing. We need to do this before we
   // orderFront any of our windows.
-  [NSWindow setAllowsAutomaticWindowTabbing:NO];
+  NSWindow.allowsAutomaticWindowTabbing = NO;
 }
 
 void nsCocoaWindow::DestroyNativeWindow() {
@@ -223,14 +197,6 @@ nsCocoaWindow::~nsCocoaWindow() {
   }
 
   NS_IF_RELEASE(mPopupContentView);
-
-  // Deal with the possiblity that we're being destroyed while running modal.
-  if (mModal) {
-    NS_WARNING("Widget destroyed while running modal!");
-    --gXULModalLevel;
-    NS_ASSERTION(gXULModalLevel >= 0, "Weirdness setting modality!");
-  }
-
   NS_OBJC_END_TRY_IGNORE_BLOCK;
 }
 
@@ -432,15 +398,6 @@ nsresult nsCocoaWindow::CreateNativeWindow(const NSRect& aRect,
     case WindowType::Dialog:
       features = WindowMaskForBorderStyle(aBorderStyle);
       break;
-    case WindowType::Sheet:
-      if (mParent->GetWindowType() != WindowType::Invisible &&
-          aBorderStyle & BorderStyle::ResizeH) {
-        features = NSWindowStyleMaskResizable;
-      } else {
-        features = NSWindowStyleMaskMiniaturizable;
-      }
-      features |= NSWindowStyleMaskTitled;
-      break;
     default:
       NS_ERROR("Unhandled window type!");
       return NS_ERROR_FAILURE;
@@ -607,14 +564,14 @@ nsresult nsCocoaWindow::CreatePopupContentView(const LayoutDeviceIntRect& aRect,
 }
 
 void nsCocoaWindow::Destroy() {
-  if (mOnDestroyCalled) return;
+  if (mOnDestroyCalled) {
+    return;
+  }
   mOnDestroyCalled = true;
 
-  // SetFakeModal(true) is called for non-modal window opened by modal window.
-  // On Cocoa, it needs corresponding SetFakeModal(false) on destroy to restore
-  // ancestor windows' state.
-  if (mFakeModal) {
-    SetFakeModal(false);
+  // Deal with the possiblity that we're being destroyed while running modal.
+  if (mModal) {
+    SetModal(false);
   }
 
   // If we don't hide here we run into problems with panels, this is not ideal.
@@ -651,14 +608,6 @@ void nsCocoaWindow::Destroy() {
   }
 }
 
-nsIWidget* nsCocoaWindow::GetSheetWindowParent(void) {
-  if (mWindowType != WindowType::Sheet) return nullptr;
-  nsCocoaWindow* parent = static_cast<nsCocoaWindow*>(mParent);
-  while (parent && (parent->mWindowType == WindowType::Sheet))
-    parent = static_cast<nsCocoaWindow*>(parent->mParent);
-  return parent;
-}
-
 void* nsCocoaWindow::GetNativeData(uint32_t aDataType) {
   NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
 
@@ -708,14 +657,18 @@ void* nsCocoaWindow::GetNativeData(uint32_t aDataType) {
 bool nsCocoaWindow::IsVisible() const {
   NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
 
-  return (mWindow && ([mWindow isVisibleOrBeingShown] || mSheetNeedsShow));
+  return mWindow && mWindow.isVisibleOrBeingShown;
 
   NS_OBJC_END_TRY_BLOCK_RETURN(false);
 }
 
-void nsCocoaWindow::SetModal(bool aState) {
+void nsCocoaWindow::SetModal(bool aModal) {
   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
 
+  if (mModal == aModal) {
+    return;
+  }
+
   // Unlike many functions here, we explicitly *do not check* for the
   // existence of mWindow. This is to ensure that calls to SetModal have
   // no early exits and always update state. That way, if the calls are
@@ -732,80 +685,47 @@ void nsCocoaWindow::SetModal(bool aState) {
   // objects leaking.
   nsAutoreleasePool localPool;
 
-  mModal = aState;
-  nsCocoaWindow* ancestor = static_cast<nsCocoaWindow*>(mAncestorLink);
-  if (aState) {
-    ++gXULModalLevel;
-    // When a non-sheet window gets "set modal", make the window(s) that it
-    // appears over behave as they should.  We can't rely on native methods to
-    // do this, for the following reason:  The OS runs modal non-sheet windows
-    // in an event loop (using [NSApplication runModalForWindow:] or similar
-    // methods) that's incompatible with the modal event loop in AppWindow::
-    // ShowModal() (each of these event loops is "exclusive", and can't run at
-    // the same time as other (similar) event loops).
-    if (mWindowType != WindowType::Sheet) {
-      while (ancestor) {
-        if (ancestor->mNumModalDescendents++ == 0) {
-          NSWindow* aWindow = ancestor->GetCocoaWindow();
-          if (ancestor->mWindowType != WindowType::Invisible) {
-            [[aWindow standardWindowButton:NSWindowCloseButton] setEnabled:NO];
-            [[aWindow standardWindowButton:NSWindowMiniaturizeButton]
-                setEnabled:NO];
-            [[aWindow standardWindowButton:NSWindowZoomButton] setEnabled:NO];
-          }
-        }
-        ancestor = static_cast<nsCocoaWindow*>(ancestor->mParent);
-      }
-      [mWindow setLevel:NSModalPanelWindowLevel];
-      nsCocoaWindowList* windowList = new nsCocoaWindowList;
-      if (windowList) {
-        windowList->window = this;  // Don't ADDREF
-        windowList->prev = gGeckoAppModalWindowList;
-        gGeckoAppModalWindowList = windowList;
-      }
-    }
+  mModal = aModal;
+
+  if (aModal) {
+    sModalWindowCount++;
   } else {
-    --gXULModalLevel;
-    NS_ASSERTION(gXULModalLevel >= 0,
-                 "Mismatched call to nsCocoaWindow::SetModal(false)!");
-    if (mWindowType != WindowType::Sheet) {
-      while (ancestor) {
-        if (--ancestor->mNumModalDescendents == 0) {
-          NSWindow* aWindow = ancestor->GetCocoaWindow();
-          if (ancestor->mWindowType != WindowType::Invisible) {
-            [[aWindow standardWindowButton:NSWindowCloseButton] setEnabled:YES];
-            [[aWindow standardWindowButton:NSWindowMiniaturizeButton]
-                setEnabled:YES];
-            [[aWindow standardWindowButton:NSWindowZoomButton] setEnabled:YES];
-          }
-        }
-        NS_ASSERTION(ancestor->mNumModalDescendents >= 0,
-                     "Widget hierarchy changed while modal!");
-        ancestor = static_cast<nsCocoaWindow*>(ancestor->mParent);
-      }
-      if (gGeckoAppModalWindowList) {
-        NS_ASSERTION(gGeckoAppModalWindowList->window == this,
-                     "Widget hierarchy changed while modal!");
-        nsCocoaWindowList* saved = gGeckoAppModalWindowList;
-        gGeckoAppModalWindowList = gGeckoAppModalWindowList->prev;
-        delete saved;  // "window" not ADDREFed
-      }
-      if (mWindowType == WindowType::Popup) {
-        SetPopupWindowLevel();
-      } else {
-        mWindow.level = NSNormalWindowLevel;
-      }
+    MOZ_ASSERT(sModalWindowCount);
+    sModalWindowCount--;
+  }
+
+  // When a window gets "set modal", make the window(s) that it appears over
+  // behave as they should.  We can't rely on native methods to do this, for the
+  // following reason:  The OS runs modal non-sheet windows in an event loop
+  // (using [NSApplication runModalForWindow:] or similar methods) that's
+  // incompatible with the modal event loop in AppWindow::ShowModal() (each of
+  // these event loops is "exclusive", and can't run at the same time as other
+  // (similar) event loops).
+  for (auto* ancestor = static_cast<nsCocoaWindow*>(mAncestorLink); ancestor;
+       ancestor = static_cast<nsCocoaWindow*>(ancestor->mParent)) {
+    const bool changed = aModal ? ancestor->mNumModalDescendants++ == 0
+                                : --ancestor->mNumModalDescendants == 0;
+    NS_ASSERTION(ancestor->mNumModalDescendants >= 0,
+                 "Widget hierarchy changed while modal!");
+    if (!changed || ancestor->mWindowType == WindowType::Invisible) {
+      continue;
     }
+    NSWindow* win = ancestor->GetCocoaWindow();
+    [[win standardWindowButton:NSWindowCloseButton] setEnabled:!aModal];
+    [[win standardWindowButton:NSWindowMiniaturizeButton] setEnabled:!aModal];
+    [[win standardWindowButton:NSWindowZoomButton] setEnabled:!aModal];
+  }
+  if (aModal) {
+    mWindow.level = NSModalPanelWindowLevel;
+  } else if (mWindowType == WindowType::Popup) {
+    SetPopupWindowLevel();
+  } else {
+    mWindow.level = NSNormalWindowLevel;
   }
 
   NS_OBJC_END_TRY_IGNORE_BLOCK;
 }
 
-void nsCocoaWindow::SetFakeModal(bool aState) {
-  mFakeModal = aState;
-  SetModal(aState);
-}
-
 bool nsCocoaWindow::IsRunningAppModal() { return [NSApp _isRunningAppModal]; }
 
 // Hide or show this window
@@ -816,12 +736,10 @@ void nsCocoaWindow::Show(bool aState) {
     return;
   }
 
-  if (!mSheetNeedsShow) {
-    // Early exit if our current visibility state is already the requested
-    // state.
-    if (aState == mWindow.isVisibleOrBeingShown) {
-      return;
-    }
+  // Early exit if our current visibility state is already the requested
+  // state.
+  if (aState == mWindow.isVisibleOrBeingShown) {
+    return;
   }
 
   [mWindow setBeingShown:aState];
@@ -829,11 +747,8 @@ void nsCocoaWindow::Show(bool aState) {
     mWasShown = true;
   }
 
-  nsIWidget* parentWidget = mParent;
-  nsCOMPtr<nsPIWidgetCocoa> piParentWidget(do_QueryInterface(parentWidget));
   NSWindow* nativeParentWindow =
-      parentWidget ? (NSWindow*)parentWidget->GetNativeData(NS_NATIVE_WINDOW)
-                   : nil;
+      mParent ? (NSWindow*)mParent->GetNativeData(NS_NATIVE_WINDOW) : nil;
 
   if (aState && !mBounds.IsEmpty()) {
     // If we had set the activationPolicy to accessory, then right now we won't
@@ -856,82 +771,7 @@ void nsCocoaWindow::Show(bool aState) {
       mPopupContentView->Show(true);
     }
 
-    if (mWindowType == WindowType::Sheet) {
-      // bail if no parent window (its basically what we do in Carbon)
-      if (!nativeParentWindow || !piParentWidget) return;
-
-      NSWindow* topNonSheetWindow = nativeParentWindow;
-
-      // If this sheet is the child of another sheet, hide the parent so that
-      // this sheet can be displayed. Leave the parent mSheetNeedsShow alone,
-      // that is only used to handle sibling sheet contention. The parent will
-      // return once there are no more child sheets.
-      bool parentIsSheet = false;
-      if (NS_SUCCEEDED(piParentWidget->GetIsSheet(&parentIsSheet)) &&
-          parentIsSheet) {
-        piParentWidget->GetSheetWindowParent(&topNonSheetWindow);
-#ifdef MOZ_THUNDERBIRD
-        [NSApp endSheet:nativeParentWindow];
-#else
-        [nativeParentWindow.sheetParent endSheet:nativeParentWindow];
-#endif
-      }
-
-      nsCOMPtr<nsIWidget> sheetShown;
-      if (NS_SUCCEEDED(piParentWidget->GetChildSheet(
-              true, getter_AddRefs(sheetShown))) &&
-          (!sheetShown || sheetShown == this)) {
-        // If this sheet is already the sheet actually being shown, don't
-        // tell it to show again. Otherwise the number of calls to
-#ifdef MOZ_THUNDERBIRD
-        // [NSApp beginSheet...] won't match up with [NSApp endSheet...].
-#else
-        // [NSWindow beginSheet...] won't match up with [NSWindow endSheet...].
-#endif
-        if (![mWindow isVisible]) {
-          mSheetNeedsShow = false;
-          mSheetWindowParent = topNonSheetWindow;
-#ifdef MOZ_THUNDERBIRD
-          // Only set contextInfo if our parent isn't a sheet.
-          NSWindow* contextInfo = parentIsSheet ? nil : mSheetWindowParent;
-          [TopLevelWindowData deactivateInWindow:mSheetWindowParent];
-          [NSApp beginSheet:mWindow
-              modalForWindow:mSheetWindowParent
-               modalDelegate:mDelegate
-              didEndSelector:@selector(didEndSheet:returnCode:contextInfo:)
-                 contextInfo:contextInfo];
-#else
-          NSWindow* sheet = mWindow;
-          NSWindow* nonSheetParent = parentIsSheet ? nil : mSheetWindowParent;
-          [TopLevelWindowData deactivateInWindow:mSheetWindowParent];
-          [mSheetWindowParent beginSheet:sheet
-                       completionHandler:^(NSModalResponse returnCode) {
-                         // Note: 'nonSheetParent' (if it is set) is the window
-                         // that is the parent of the sheet. If it's set,
-                         // 'nonSheetParent' is always the top- level window,
-                         // not another sheet itself.  But 'nonSheetParent' is
-                         // nil if our parent window is also a sheet -- in that
-                         // case we shouldn't send the top-level window any
-                         // activate events (because it's our parent window that
-                         // needs to get these events, not the top-level
-                         // window).
-                         [TopLevelWindowData deactivateInWindow:sheet];
-                         [sheet orderOut:nil];
-                         if (nonSheetParent) {
-                           [TopLevelWindowData activateInWindow:nonSheetParent];
-                         }
-                       }];
-#endif
-          [TopLevelWindowData activateInWindow:mWindow];
-          SendSetZLevelEvent();
-        }
-      } else {
-        // A sibling of this sheet is active, don't show this sheet yet.
-        // When the active sheet hides, its brothers and sisters that have
-        // mSheetNeedsShow set will have their opportunities to display.
-        mSheetNeedsShow = true;
-      }
-    } else if (mWindowType == WindowType::Popup) {
+    if (mWindowType == WindowType::Popup) {
       // For reasons that aren't yet clear, calls to [NSWindow orderFront:] or
       // [NSWindow makeKeyAndOrderFront:] can sometimes trigger "Error (1000)
       // creating CGSWindow", which in turn triggers an internal inconsistency
@@ -939,7 +779,9 @@ void nsCocoaWindow::Show(bool aState) {
       // calls to ...orderFront: in TRY blocks.  See bmo bug 470864.
       NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
       [[mWindow contentView] setNeedsDisplay:YES];
-      [mWindow orderFront:nil];
+      if (!nativeParentWindow || mPopupLevel != PopupLevel::Parent) {
+        [mWindow orderFront:nil];
+      }
       NS_OBJC_END_TRY_IGNORE_BLOCK;
       SendSetZLevelEvent();
       // If our popup window is a non-native context menu, tell the OS (and
@@ -955,9 +797,7 @@ void nsCocoaWindow::Show(bool aState) {
 
       // If a parent window was supplied and this is a popup at the parent
       // level, set its child window. This will cause the child window to
-      // appear above the parent and move when the parent does. Setting this
-      // needs to happen after the _setWindowNumber calls above, otherwise the
-      // window doesn't focus properly.
+      // appear above the parent and move when the parent does.
       if (nativeParentWindow && mPopupLevel == PopupLevel::Parent) {
         [nativeParentWindow addChildWindow:mWindow ordered:NSWindowAbove];
       }
@@ -1001,120 +841,22 @@ void nsCocoaWindow::Show(bool aState) {
       RollUpPopups();
     }
 
-    // now get rid of the window/sheet
-    if (mWindowType == WindowType::Sheet) {
-      if (mSheetNeedsShow) {
-        // This is an attempt to hide a sheet that never had a chance to
-        // be shown. There's nothing to do other than make sure that it
-        // won't show.
-        mSheetNeedsShow = false;
-      } else {
-        // get sheet's parent *before* hiding the sheet (which breaks the
-        // linkage)
-        NSWindow* sheetParent = mSheetWindowParent;
-
-        // hide the sheet
-#ifdef MOZ_THUNDERBIRD
-        [NSApp endSheet:mWindow];
-#else
-        [mSheetWindowParent endSheet:mWindow];
-#endif
-        [TopLevelWindowData deactivateInWindow:mWindow];
-
-        nsCOMPtr<nsIWidget> siblingSheetToShow;
-        bool parentIsSheet = false;
-
-        if (nativeParentWindow && piParentWidget &&
-            NS_SUCCEEDED(piParentWidget->GetChildSheet(
-                false, getter_AddRefs(siblingSheetToShow))) &&
-            siblingSheetToShow) {
-          // First, give sibling sheets an opportunity to show.
-          siblingSheetToShow->Show(true);
-        } else if (nativeParentWindow && piParentWidget &&
-                   NS_SUCCEEDED(piParentWidget->GetIsSheet(&parentIsSheet)) &&
-                   parentIsSheet) {
-#ifdef MOZ_THUNDERBIRD
-          // Only set contextInfo if the parent of the parent sheet we're about
-          // to restore isn't itself a sheet.
-          NSWindow* contextInfo = sheetParent;
-#else
-          // Only set nonSheetGrandparent if the parent of the parent sheet
-          // we're about to restore isn't itself a sheet.
-          NSWindow* nonSheetGrandparent = sheetParent;
-#endif
-          nsIWidget* grandparentWidget = nil;
-          if (NS_SUCCEEDED(piParentWidget->GetRealParent(&grandparentWidget)) &&
-              grandparentWidget) {
-            nsCOMPtr<nsPIWidgetCocoa> piGrandparentWidget(
-                do_QueryInterface(grandparentWidget));
-            bool grandparentIsSheet = false;
-            if (piGrandparentWidget &&
-                NS_SUCCEEDED(
-                    piGrandparentWidget->GetIsSheet(&grandparentIsSheet)) &&
-                grandparentIsSheet) {
-#ifdef MOZ_THUNDERBIRD
-              contextInfo = nil;
-#else
-              nonSheetGrandparent = nil;
-#endif
-            }
-          }
-          // If there are no sibling sheets, but the parent is a sheet, restore
-          // it.  It wasn't sent any deactivate events when it was hidden, so
-          // don't call through Show, just let the OS put it back up.
-#ifdef MOZ_THUNDERBIRD
-          [NSApp beginSheet:nativeParentWindow
-              modalForWindow:sheetParent
-               modalDelegate:[nativeParentWindow delegate]
-              didEndSelector:@selector(didEndSheet:returnCode:contextInfo:)
-                 contextInfo:contextInfo];
-#else
-          [nativeParentWindow
-                     beginSheet:sheetParent
-              completionHandler:^(NSModalResponse returnCode) {
-                // Note: 'nonSheetGrandparent' (if it is set) is the window that
-                // is the parent of sheetParent. If it's set,
-                // 'nonSheetGrandparent' is always the top-level window, not
-                // another sheet itself.  But 'nonSheetGrandparent' is nil if
-                // our parent window is also a sheet -- in that case we
-                // shouldn't send the top-level window any activate events
-                // (because it's our parent window that needs to get these
-                // events, not the top-level window).
-                [TopLevelWindowData deactivateInWindow:sheetParent];
-                [sheetParent orderOut:nil];
-                if (nonSheetGrandparent) {
-                  [TopLevelWindowData activateInWindow:nonSheetGrandparent];
-                }
-              }];
-#endif
-        } else {
-          // Sheet, that was hard.  No more siblings or parents, going back
-          // to a real window.
-          NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
-          [sheetParent makeKeyAndOrderFront:nil];
-          NS_OBJC_END_TRY_IGNORE_BLOCK;
-        }
-        SendSetZLevelEvent();
-      }
-    } else {
-      // If the window is a popup window with a parent window we need to
-      // unhook it here before ordering it out. When you order out the child
-      // of a window it hides the parent window.
-      if (mWindowType == WindowType::Popup && nativeParentWindow) {
-        [nativeParentWindow removeChildWindow:mWindow];
-      }
-
-      [mWindow orderOut:nil];
+    // If the window is a popup window with a parent window we need to
+    // unhook it here before ordering it out. When you order out the child
+    // of a window it hides the parent window.
+    if (mWindowType == WindowType::Popup && nativeParentWindow) {
+      [nativeParentWindow removeChildWindow:mWindow];
+    }
 
-      // If our popup window is a non-native context menu, tell the OS (and
-      // other programs) that a menu has closed.
-      if ([mWindow isKindOfClass:[PopupWindow class]] &&
-          [(PopupWindow*)mWindow isContextMenu]) {
-        [[NSDistributedNotificationCenter defaultCenter]
-            postNotificationName:
-                @"com.apple.HIToolbox.endMenuTrackingNotification"
-                          object:@"org.mozilla.gecko.PopupWindow"];
-      }
+    [mWindow orderOut:nil];
+    // If our popup window is a non-native context menu, tell the OS (and
+    // other programs) that a menu has closed.
+    if ([mWindow isKindOfClass:[PopupWindow class]] &&
+        [(PopupWindow*)mWindow isContextMenu]) {
+      [NSDistributedNotificationCenter.defaultCenter
+          postNotificationName:
+              @"com.apple.HIToolbox.endMenuTrackingNotification"
+                        object:@"org.mozilla.gecko.PopupWindow"];
     }
   }
 
@@ -2287,53 +2029,13 @@ bool nsCocoaWindow::DragEvent(unsigned int aMessage,
   return false;
 }
 
-NS_IMETHODIMP nsCocoaWindow::SendSetZLevelEvent() {
-  nsWindowZ placement = nsWindowZTop;
-  nsCOMPtr<nsIWidget> actualBelow;
+void nsCocoaWindow::SendSetZLevelEvent() {
   if (mWidgetListener) {
+    nsWindowZ placement = nsWindowZTop;
+    nsCOMPtr<nsIWidget> actualBelow;
     mWidgetListener->ZLevelChanged(true, &placement, nullptr,
                                    getter_AddRefs(actualBelow));
   }
-  return NS_OK;
-}
-
-NS_IMETHODIMP nsCocoaWindow::GetChildSheet(bool aShown, nsIWidget** _retval) {
-  nsIWidget* child = GetFirstChild();
-
-  while (child) {
-    if (child->GetWindowType() == WindowType::Sheet) {
-      // if it's a sheet, it must be an nsCocoaWindow
-      nsCocoaWindow* cocoaWindow = static_cast<nsCocoaWindow*>(child);
-      if (cocoaWindow->mWindow &&
-          ((aShown && [cocoaWindow->mWindow isVisible]) ||
-           (!aShown && cocoaWindow->mSheetNeedsShow))) {
-        nsCOMPtr<nsIWidget> widget = cocoaWindow;
-        widget.forget(_retval);
-        return NS_OK;
-      }
-    }
-    child = child->GetNextSibling();
-  }
-
-  *_retval = nullptr;
-
-  return NS_OK;
-}
-
-NS_IMETHODIMP nsCocoaWindow::GetRealParent(nsIWidget** parent) {
-  *parent = mParent;
-  return NS_OK;
-}
-
-NS_IMETHODIMP nsCocoaWindow::GetIsSheet(bool* isSheet) {
-  mWindowType == WindowType::Sheet ? * isSheet = true : * isSheet = false;
-  return NS_OK;
-}
-
-NS_IMETHODIMP nsCocoaWindow::GetSheetWindowParent(
-    NSWindow** sheetWindowParent) {
-  *sheetWindowParent = mSheetWindowParent;
-  return NS_OK;
 }
 
 // Invokes callback and ProcessEvent methods on Event Listener object
@@ -3184,9 +2886,7 @@ void nsCocoaWindow::CocoaWindowDidResize() {
   ChildViewMouseTracker::ReEvaluateMouseEnterState();
 
   NSWindow* window = [aNotification object];
-  if ([window isSheet]) [WindowDelegate paintMenubarForWindow:window];
-
-  nsChildView* mainChildView =
+  auto* mainChildView =
       static_cast<nsChildView*>([[(BaseWindow*)window mainChildView] widget]);
   if (mainChildView) {
     if (mainChildView->GetInputContext().IsPasswordEditor()) {
@@ -3205,13 +2905,6 @@ void nsCocoaWindow::CocoaWindowDidResize() {
   RollUpPopups(nsIRollupListener::AllowAnimations::No);
 
   ChildViewMouseTracker::ReEvaluateMouseEnterState();
-
-  // If a sheet just resigned key then we should paint the menu bar
-  // for whatever window is now main.
-  NSWindow* window = [aNotification object];
-  if ([window isSheet])
-    [WindowDelegate paintMenubarForWindow:[NSApp mainWindow]];
-
   TextInputHandler::EnsureSecureEventInputDisabled();
 
   NS_OBJC_END_TRY_IGNORE_BLOCK;
@@ -3264,36 +2957,6 @@ void nsCocoaWindow::CocoaWindowDidResize() {
   return YES;
 }
 
-- (NSRect)window:(NSWindow*)window
-    willPositionSheet:(NSWindow*)sheet
-            usingRect:(NSRect)rect {
-  if ([window isKindOfClass:[ToolbarWindow class]]) {
-    rect.origin.y = [(ToolbarWindow*)window sheetAttachmentPosition];
-  }
-  return rect;
-}
-
-#ifdef MOZ_THUNDERBIRD
-- (void)didEndSheet:(NSWindow*)sheet
-         returnCode:(int)returnCode
-        contextInfo:(void*)contextInfo {
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
-
-  // Note: 'contextInfo' (if it is set) is the window that is the parent of
-  // the sheet.  The value of contextInfo is determined in
-  // nsCocoaWindow::Show().  If it's set, 'contextInfo' is always the top-
-  // level window, not another sheet itself.  But 'contextInfo' is nil if
-  // our parent window is also a sheet -- in that case we shouldn't send
-  // the top-level window any activate events (because it's our parent
-  // window that needs to get these events, not the top-level window).
-  [TopLevelWindowData deactivateInWindow:sheet];
-  [sheet orderOut:self];
-  if (contextInfo) [TopLevelWindowData activateInWindow:(NSWindow*)contextInfo];
-
-  NS_OBJC_END_TRY_ABORT_BLOCK;
-}
-#endif
-
 - (void)windowDidChangeBackingProperties:(NSNotification*)aNotification {
   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
 
@@ -3354,7 +3017,7 @@ void nsCocoaWindow::CocoaWindowDidResize() {
     return self.FrameView__closeButtonOrigin;
   }
   auto* win = static_cast<ToolbarWindow*>(self.window);
-  if (win.drawsContentsIntoWindowFrame &&
+  if (win.drawsContentsIntoWindowFrame && !win.wantsTitleDrawn &&
       !(win.styleMask & NSWindowStyleMaskFullScreen) &&
       (win.styleMask & NSWindowStyleMaskTitled)) {
     const NSRect buttonsRect = win.windowButtonsRect;
@@ -3624,7 +3287,7 @@ static const NSString* kStateWantsTitleDrawn = @"wantsTitleDrawn";
 }
 
 - (void)setDrawsContentsIntoWindowFrame:(BOOL)aState {
-  bool changed = (aState != mDrawsIntoWindowFrame);
+  bool changed = aState != mDrawsIntoWindowFrame;
   mDrawsIntoWindowFrame = aState;
   if (changed) {
     [self reflowTitlebarElements];
@@ -3826,53 +3489,6 @@ static const NSString* kStateWantsTitleDrawn = @"wantsTitleDrawn";
 
 @end
 
-@interface NSView (NSThemeFrame)
-- (void)_drawTitleStringInClip:(NSRect)aRect;
-- (void)_maskCorners:(NSUInteger)aFlags clipRect:(NSRect)aRect;
-@end
-
-@implementation MOZTitlebarView
-
-- (instancetype)initWithFrame:(NSRect)aFrame {
-  self = [super initWithFrame:aFrame];
-
-  self.material = NSVisualEffectMaterialTitlebar;
-  self.blendingMode = NSVisualEffectBlendingModeWithinWindow;
-
-  // Add a separator line at the bottom of the titlebar. NSBoxSeparator isn't a
-  // perfect match for a native titlebar separator, but it's better than
-  // nothing. We really want the appearance that _NSTitlebarDecorationView
-  // creates with the help of CoreUI, but there's no public API for that.
-  NSBox* separatorLine =
-      [[NSBox alloc] initWithFrame:NSMakeRect(0, 0, aFrame.size.width, 1)];
-  separatorLine.autoresizingMask = NSViewWidthSizable | NSViewMaxYMargin;
-  separatorLine.boxType = NSBoxSeparator;
-  [self addSubview:separatorLine];
-  [separatorLine release];
-
-  return self;
-}
-
-- (BOOL)mouseDownCanMoveWindow {
-  return YES;
-}
-
-- (void)mouseUp:(NSEvent*)event {
-  if (event.clickCount == 2) {
-    // Handle titlebar double click. We don't get the window's default behavior
-    // here because the window uses NSWindowStyleMaskFullSizeContentView, and
-    // this view (the titlebar gradient view) is technically part of the window
-    // "contents" (it's a subview of the content view).
-    if (nsCocoaUtils::ShouldZoomOnTitlebarDoubleClick()) {
-      [self.window performZoom:nil];
-    } else if (nsCocoaUtils::ShouldMinimizeOnTitlebarDoubleClick()) {
-      [self.window performMiniaturize:nil];
-    }
-  }
-}
-
-@end
-
 @interface MOZTitlebarAccessoryView : NSView
 @end
 
@@ -3896,44 +3512,51 @@ static const NSString* kStateWantsTitleDrawn = @"wantsTitleDrawn";
 @implementation FullscreenTitlebarTracker
 - (FullscreenTitlebarTracker*)init {
   [super init];
-  self.view =
-      [[[MOZTitlebarAccessoryView alloc] initWithFrame:NSZeroRect] autorelease];
   self.hidden = YES;
   return self;
 }
+- (void)loadView {
+  self.view =
+      [[[MOZTitlebarAccessoryView alloc] initWithFrame:NSZeroRect] autorelease];
+}
 @end
 
-// This class allows us to exercise control over the window's title bar. It is
-// used for all windows with titlebars.
-//
-// ToolbarWindow supports two modes:
-//  - drawsContentsIntoWindowFrame mode: In this mode, the Gecko ChildView is
-//    sized to cover the entire window frame and manages titlebar drawing.
-//  - separate titlebar mode, with support for unified toolbars: In this mode,
-//    the Gecko ChildView does not extend into the titlebar. However, this
-//    window's content view (which is the ChildView's superview) *does* extend
-//    into the titlebar. Moreover, in this mode, we place a MOZTitlebarView
-//    in the content view, as a sibling of the ChildView.
-//
-// The "separate titlebar mode" supports the "unified toolbar" look:
-// If there's a toolbar right below the titlebar, the two can "connect" and
-// form a single gradient without a separator line in between.
-//
-// The following mechanism communicates the height of the unified toolbar to
-// the ToolbarWindow:
-//
-// 1) In the style sheet we set the toolbar's -moz-appearance to toolbar.
-// 2) When the toolbar is visible and we paint the application chrome
-//    window, the array that Gecko passes nsChildView::UpdateThemeGeometries
-//    will contain an entry for the widget type StyleAppearance::Toolbar.
-// 3) nsChildView::UpdateThemeGeometries passes the toolbar's height, plus the
-//    titlebar height, to -[ToolbarWindow setUnifiedToolbarHeight:].
-//
-// The actual drawing of the gradient happens in two parts: The titlebar part
-// (i.e. the top 22 pixels of the gradient) is drawn by the MOZTitlebarView,
-// which is a subview of the window's content view and a sibling of the
-// ChildView. The rest of the gradient is drawn by Gecko into the ChildView, as
-// part of the -moz-appearance rendering of the toolbar.
+// Drop all mouse events if a modal window has appeared above us.
+// This helps make us behave as if the OS were running a "real" modal event
+// loop.
+static bool MaybeDropEventForModalWindow(NSEvent* aEvent, id aDelegate) {
+  if (!sModalWindowCount) {
+    return false;
+  }
+
+  NSEventType type = [aEvent type];
+  switch (type) {
+    case NSEventTypeScrollWheel:
+    case NSEventTypeLeftMouseDown:
+    case NSEventTypeLeftMouseUp:
+    case NSEventTypeRightMouseDown:
+    case NSEventTypeRightMouseUp:
+    case NSEventTypeOtherMouseDown:
+    case NSEventTypeOtherMouseUp:
+    case NSEventTypeMouseMoved:
+    case NSEventTypeLeftMouseDragged:
+    case NSEventTypeRightMouseDragged:
+    case NSEventTypeOtherMouseDragged:
+      break;
+    default:
+      return false;
+  }
+
+  if (aDelegate && [aDelegate isKindOfClass:[WindowDelegate class]]) {
+    if (nsCocoaWindow* widget = [(WindowDelegate*)aDelegate geckoWidget]) {
+      if (!widget->IsModal() || widget->HasModalDescendants()) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 @implementation ToolbarWindow
 
 - (id)initWithContentRect:(NSRect)aChildViewRect
@@ -3972,17 +3595,12 @@ static const NSString* kStateWantsTitleDrawn = @"wantsTitleDrawn";
                                styleMask:aStyle
                                  backing:aBufferingType
                                    defer:aFlag])) {
-    mTitlebarView = nil;
-    mUnifiedToolbarHeight = 22.0f;
-    mSheetAttachmentPosition = aChildViewRect.size.height;
     mWindowButtonsRect = NSZeroRect;
-    mInitialTitlebarHeight = [self titlebarHeight];
 
-    [self setTitlebarAppearsTransparent:YES];
+    self.titlebarAppearsTransparent = YES;
     if (@available(macOS 11.0, *)) {
       self.titlebarSeparatorStyle = NSTitlebarSeparatorStyleNone;
     }
-    [self updateTitlebarView];
 
     mFullscreenTitlebarTracker = [[FullscreenTitlebarTracker alloc] init];
     // revealAmount is an undocumented property of
@@ -4048,8 +3666,7 @@ static bool ShouldShiftByMenubarHeightInFullscreen(nsCocoaWindow* aWindow) {
 }
 
 - (void)updateTitlebarShownAmount:(CGFloat)aShownAmount {
-  NSInteger styleMask = [self styleMask];
-  if (!(styleMask & NSWindowStyleMaskFullScreen)) {
+  if (!(self.styleMask & NSWindowStyleMaskFullScreen)) {
     // We are not interested in the size of the titlebar unless we are in
     // fullscreen.
     return;
@@ -4071,27 +3688,24 @@ static bool ShouldShiftByMenubarHeightInFullscreen(nsCocoaWindow* aWindow) {
     }
 
     if (nsIWidgetListener* listener = geckoWindow->GetWidgetListener()) {
-      // Use the titlebar height cached in our frame rather than
-      // [ToolbarWindow titlebarHeight]. titlebarHeight returns 0 when we're in
-      // fullscreen.
-      CGFloat shiftByPixels = mInitialTitlebarHeight * aShownAmount;
+      // titlebarHeight returns 0 when we're in fullscreen, return the default
+      // titlebar height.
+      CGFloat shiftByPixels =
+          LookAndFeel::GetInt(LookAndFeel::IntID::MacTitlebarHeight) *
+          aShownAmount;
       if (ShouldShiftByMenubarHeightInFullscreen(geckoWindow)) {
         shiftByPixels += mMenuBarHeight * aShownAmount;
       }
-      // Use mozilla::DesktopToLayoutDeviceScale rather than the
-      // DesktopToLayoutDeviceScale in nsCocoaWindow. The latter accounts for
-      // screen DPI. We don't want that because the revealAmount property
-      // already accounts for it, so we'd be compounding DPI scales > 1.
-      mozilla::DesktopCoord coord = LayoutDeviceCoord(shiftByPixels) /
-                                    mozilla::DesktopToLayoutDeviceScale();
-
-      listener->MacFullscreenMenubarOverlapChanged(coord);
+      // Use desktop pixels rather than the DesktopToLayoutDeviceScale in
+      // nsCocoaWindow. The latter accounts for screen DPI. We don't want that
+      // because the revealAmount property already accounts for it, so we'd be
+      // compounding DPI scales > 1.
+      listener->MacFullscreenMenubarOverlapChanged(DesktopCoord(shiftByPixels));
     }
   }
 }
 
 - (void)dealloc {
-  [mTitlebarView release];
   [mFullscreenTitlebarTracker removeObserver:self forKeyPath:@"revealAmount"];
   [mFullscreenTitlebarTracker removeFromParentViewController];
   [mFullscreenTitlebarTracker release];
@@ -4100,80 +3714,13 @@ static bool ShouldShiftByMenubarHeightInFullscreen(nsCocoaWindow* aWindow) {
 }
 
 - (NSArray<NSView*>*)contentViewContents {
-  NSMutableArray<NSView*>* contents = [[self.contentView subviews] mutableCopy];
-  if (mTitlebarView) {
-    // Do not include the titlebar gradient view in the returned array.
-    [contents removeObject:mTitlebarView];
-  }
-  return [contents autorelease];
-}
-
-- (void)updateTitlebarView {
-  BOOL needTitlebarView =
-      !self.drawsContentsIntoWindowFrame || mUnifiedToolbarHeight > 0;
-  if (needTitlebarView && !mTitlebarView) {
-    mTitlebarView =
-        [[MOZTitlebarView alloc] initWithFrame:self.unifiedToolbarRect];
-    mTitlebarView.autoresizingMask = NSViewWidthSizable | NSViewMinYMargin;
-    [self.contentView addSubview:mTitlebarView
-                      positioned:NSWindowBelow
-                      relativeTo:nil];
-  } else if (needTitlebarView && mTitlebarView) {
-    mTitlebarView.frame = self.unifiedToolbarRect;
-  } else if (!needTitlebarView && mTitlebarView) {
-    [mTitlebarView removeFromSuperview];
-    [mTitlebarView release];
-    mTitlebarView = nil;
-  }
+  return [[self.contentView.subviews copy] autorelease];
 }
 
 - (void)windowMainStateChanged {
-  [self setTitlebarNeedsDisplay];
   [[self mainChildView] ensureNextCompositeIsAtomicWithMainThreadPaint];
 }
 
-- (void)setTitlebarNeedsDisplay {
-  [mTitlebarView setNeedsDisplay:YES];
-}
-
-- (NSRect)titlebarRect {
-  CGFloat titlebarHeight = self.titlebarHeight;
-  return NSMakeRect(0, self.frame.size.height - titlebarHeight,
-                    self.frame.size.width, titlebarHeight);
-}
-
-// In window contentView coordinates (origin bottom left)
-- (NSRect)unifiedToolbarRect {
-  return NSMakeRect(0, self.frame.size.height - mUnifiedToolbarHeight,
-                    self.frame.size.width, mUnifiedToolbarHeight);
-}
-
-// Returns the unified height of titlebar + toolbar.
-- (CGFloat)unifiedToolbarHeight {
-  return mUnifiedToolbarHeight;
-}
-
-- (CGFloat)titlebarHeight {
-  // We use the original content rect here, not what we return from
-  // [self contentRectForFrameRect:], because that would give us a
-  // titlebarHeight of zero.
-  NSRect frameRect = self.frame;
-  NSUInteger styleMask = self.styleMask;
-  styleMask &= ~NSWindowStyleMaskFullSizeContentView;
-  NSRect originalContentRect = [NSWindow contentRectForFrameRect:frameRect
-                                                       styleMask:styleMask];
-  return NSMaxY(frameRect) - NSMaxY(originalContentRect);
-}
-
-// Stores the complete height of titlebar + toolbar.
-- (void)setUnifiedToolbarHeight:(CGFloat)aHeight {
-  if (aHeight == mUnifiedToolbarHeight) return;
-
-  mUnifiedToolbarHeight = aHeight;
-
-  [self updateTitlebarView];
-}
-
 // Extending the content area into the title bar works by resizing the
 // mainChildView so that it covers the titlebar.
 - (void)setDrawsContentsIntoWindowFrame:(BOOL)aState {
@@ -4197,21 +3744,6 @@ static bool ShouldShiftByMenubarHeightInFullscreen(nsCocoaWindow* aWindow) {
     // we'll send a mouse move event with the correct new position.
     ChildViewMouseTracker::ResendLastMouseMoveEvent();
   }
-
-  [self updateTitlebarView];
-}
-
-- (void)setWantsTitleDrawn:(BOOL)aDrawTitle {
-  [super setWantsTitleDrawn:aDrawTitle];
-  [self setTitlebarNeedsDisplay];
-}
-
-- (void)setSheetAttachmentPosition:(CGFloat)aY {
-  mSheetAttachmentPosition = aY;
-}
-
-- (CGFloat)sheetAttachmentPosition {
-  return mSheetAttachmentPosition;
 }
 
 - (void)placeWindowButtons:(NSRect)aRect {
@@ -4268,42 +3800,9 @@ static bool ShouldShiftByMenubarHeightInFullscreen(nsCocoaWindow* aWindow) {
 }
 
 - (void)sendEvent:(NSEvent*)anEvent {
-  NSEventType type = [anEvent type];
-
-  switch (type) {
-    case NSEventTypeScrollWheel:
-    case NSEventTypeLeftMouseDown:
-    case NSEventTypeLeftMouseUp:
-    case NSEventTypeRightMouseDown:
-    case NSEventTypeRightMouseUp:
-    case NSEventTypeOtherMouseDown:
-    case NSEventTypeOtherMouseUp:
-    case NSEventTypeMouseMoved:
-    case NSEventTypeLeftMouseDragged:
-    case NSEventTypeRightMouseDragged:
-    case NSEventTypeOtherMouseDragged: {
-      // Drop all mouse events if a modal window has appeared above us.
-      // This helps make us behave as if the OS were running a "real" modal
-      // event loop.
-      id delegate = self.delegate;
-      if (delegate && [delegate isKindOfClass:[WindowDelegate class]]) {
-        nsCocoaWindow* widget = [(WindowDelegate*)delegate geckoWidget];
-        if (widget) {
-          if (gGeckoAppModalWindowList &&
-              widget != gGeckoAppModalWindowList->window) {
-            return;
-          }
-          if (widget->HasModalDescendents()) {
-            return;
-          }
-        }
-      }
-      break;
-    }
-    default:
-      break;
+  if (MaybeDropEventForModalWindow(anEvent, self.delegate)) {
+    return;
   }
-
   [super sendEvent:anEvent];
 }
 
@@ -4403,40 +3902,8 @@ static const NSUInteger kWindowShadowOptionsTooltip = 4;
 }
 
 - (void)sendEvent:(NSEvent*)anEvent {
-  NSEventType type = [anEvent type];
-
-  switch (type) {
-    case NSEventTypeScrollWheel:
-    case NSEventTypeLeftMouseDown:
-    case NSEventTypeLeftMouseUp:
-    case NSEventTypeRightMouseDown:
-    case NSEventTypeRightMouseUp:
-    case NSEventTypeOtherMouseDown:
-    case NSEventTypeOtherMouseUp:
-    case NSEventTypeMouseMoved:
-    case NSEventTypeLeftMouseDragged:
-    case NSEventTypeRightMouseDragged:
-    case NSEventTypeOtherMouseDragged: {
-      // Drop all mouse events if a modal window has appeared above us.
-      // This helps make us behave as if the OS were running a "real" modal
-      // event loop.
-      id delegate = self.delegate;
-      if (delegate && [delegate isKindOfClass:[WindowDelegate class]]) {
-        nsCocoaWindow* widget = [(WindowDelegate*)delegate geckoWidget];
-        if (widget) {
-          if (gGeckoAppModalWindowList &&
-              widget != gGeckoAppModalWindowList->window) {
-            return;
-          }
-          if (widget->HasModalDescendents()) {
-            return;
-          }
-        }
-      }
-      break;
-    }
-    default:
-      break;
+  if (MaybeDropEventForModalWindow(anEvent, self.delegate)) {
+    return;
   }
 
   [super sendEvent:anEvent];
diff --git a/widget/cocoa/nsLookAndFeel.h b/widget/cocoa/nsLookAndFeel.h
index adce685a4e..89e4c93713 100644
--- a/widget/cocoa/nsLookAndFeel.h
+++ b/widget/cocoa/nsLookAndFeel.h
@@ -12,14 +12,17 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
   nsLookAndFeel();
   virtual ~nsLookAndFeel();
 
-  void NativeInit() final;
+  void NativeInit() final { EnsureInit(); }
+  void RefreshImpl() final;
+  void EnsureInit();
+
   nsresult NativeGetColor(ColorID, ColorScheme, nscolor& aColor) override;
   nsresult NativeGetInt(IntID, int32_t& aResult) override;
   nsresult NativeGetFloat(FloatID, float& aResult) override;
   bool NativeGetFont(FontID aID, nsString& aFontName,
                      gfxFontStyle& aFontStyle) override;
 
-  virtual char16_t GetPasswordCharacterImpl() override {
+  char16_t GetPasswordCharacterImpl() override {
     // unicode value for the bullet character, used for password textfields.
     return 0x2022;
   }
@@ -34,10 +37,9 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
   static void RecordAccessibilityTelemetry();
 
  protected:
-  static bool SystemWantsDarkTheme();
-  static bool IsSystemOrientationRTL();
-  static nscolor ProcessSelectionBackground(nscolor aColor,
-                                            ColorScheme aScheme);
+  bool mInitialized = false;
+  bool mRtl = false;
+  int32_t mTitlebarHeight = 0;
 };
 
 #endif  // nsLookAndFeel_h_
diff --git a/widget/cocoa/nsLookAndFeel.mm b/widget/cocoa/nsLookAndFeel.mm
index 5675198ff2..779984be0c 100644
--- a/widget/cocoa/nsLookAndFeel.mm
+++ b/widget/cocoa/nsLookAndFeel.mm
@@ -32,22 +32,44 @@ using namespace mozilla;
 + (void)startObserving;
 @end
 
-nsLookAndFeel::nsLookAndFeel() = default;
+nsLookAndFeel::nsLookAndFeel() {
+  [MOZLookAndFeelDynamicChangeObserver startObserving];
+}
 
 nsLookAndFeel::~nsLookAndFeel() = default;
 
-void nsLookAndFeel::NativeInit() {
+void nsLookAndFeel::EnsureInit() {
+  if (mInitialized) {
+    return;
+  }
+
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK
 
-  [MOZLookAndFeelDynamicChangeObserver startObserving];
+  mInitialized = true;
+  NSWindow* window =
+      [[NSWindow alloc] initWithContentRect:NSZeroRect
+                                  styleMask:NSWindowStyleMaskTitled
+                                    backing:NSBackingStoreBuffered
+                                      defer:NO];
+  auto release = MakeScopeExit([&] { [window release]; });
+
+  mRtl = window.windowTitlebarLayoutDirection ==
+         NSUserInterfaceLayoutDirectionRightToLeft;
+  mTitlebarHeight = std::ceil(window.frame.size.height);
+
   RecordTelemetry();
 
   NS_OBJC_END_TRY_ABORT_BLOCK
 }
 
+void nsLookAndFeel::RefreshImpl() {
+  mInitialized = false;
+  nsXPLookAndFeel::RefreshImpl();
+}
+
 static nscolor GetColorFromNSColor(NSColor* aColor) {
   NSColor* deviceColor =
-      [aColor colorUsingColorSpace:[NSColorSpace deviceRGBColorSpace]];
+      [aColor colorUsingColorSpace:NSColorSpace.deviceRGBColorSpace];
   return NS_RGBA((unsigned int)(deviceColor.redComponent * 255.0),
                  (unsigned int)(deviceColor.greenComponent * 255.0),
                  (unsigned int)(deviceColor.blueComponent * 255.0),
@@ -77,8 +99,7 @@ static nscolor GetColorFromNSColorWithCustomAlpha(NSColor* aColor,
 // whereas white text on dark blue (which what you get if you mix
 // partially-transparent light blue with the black textbox background) has much
 // better contrast.
-nscolor nsLookAndFeel::ProcessSelectionBackground(nscolor aColor,
-                                                  ColorScheme aScheme) {
+static nscolor ProcessSelectionBackground(nscolor aColor, ColorScheme aScheme) {
   if (aScheme == ColorScheme::Dark) {
     // When we use a dark selection color, we do not change alpha because we do
     // not use dark selection in content. The dark system color is appropriate
@@ -136,6 +157,14 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme,
     case ColorID::MozMenuhover:
     case ColorID::Selecteditem:
       color = GetColorFromNSColor(NSColor.selectedContentBackgroundColor);
+      if (aID == ColorID::MozMenuhover &&
+          !LookAndFeel::GetInt(IntID::PrefersReducedTransparency)) {
+        // Wash the color a little bit with semi-transparent white to match a
+        // bit closer the native NSVisualEffectSelection on menus.
+        color = NS_ComposeColors(
+            color,
+            NS_RGBA(255, 255, 255, aScheme == ColorScheme::Light ? 51 : 25));
+      }
       break;
     case ColorID::Accentcolortext:
     case ColorID::MozMenuhovertext:
@@ -197,6 +226,7 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme,
                   : NS_RGB(0xFF, 0xFF, 0xFF);
       break;
     case ColorID::Windowtext:
+    case ColorID::MozDialogtext:
       color = GetColorFromNSColor(NSColor.windowFrameTextColor);
       break;
     case ColorID::Appworkspace:
@@ -254,13 +284,14 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme,
     case ColorID::Windowframe:
       color = GetColorFromNSColor(NSColor.windowFrameColor);
       break;
-    case ColorID::Window: {
-      color = GetColorFromNSColor(NSColor.windowBackgroundColor);
+    case ColorID::MozDialog:
+    case ColorID::Window:
+      color = GetColorFromNSColor(aScheme == ColorScheme::Light
+                                      ? NSColor.windowBackgroundColor
+                                      : NSColor.underPageBackgroundColor);
       break;
-    }
     case ColorID::Field:
     case ColorID::MozCombobox:
-    case ColorID::MozDialog:
       color = GetColorFromNSColor(NSColor.controlBackgroundColor);
       break;
     case ColorID::Fieldtext:
@@ -269,7 +300,6 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme,
     case ColorID::MozButtonhovertext:
     case ColorID::Menutext:
     case ColorID::Infotext:
-    case ColorID::MozDialogtext:
     case ColorID::MozCellhighlighttext:
     case ColorID::MozColheadertext:
     case ColorID::MozColheaderhovertext:
@@ -323,6 +353,7 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme,
     case ColorID::SpellCheckerUnderline:
     case ColorID::Activeborder:
     case ColorID::Inactiveborder:
+    case ColorID::MozAutofillBackground:
       aColor = GetStandinForNativeColor(aID, aScheme);
       return NS_OK;
     default:
@@ -336,6 +367,16 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme,
   NS_OBJC_END_TRY_ABORT_BLOCK
 }
 
+static bool SystemWantsDarkTheme() {
+  // This returns true if the macOS system appearance is set to dark mode,
+  // false otherwise.
+  NSAppearanceName aquaOrDarkAqua =
+      [NSApp.effectiveAppearance bestMatchFromAppearancesWithNames:@[
+        NSAppearanceNameAqua, NSAppearanceNameDarkAqua
+      ]];
+  return [aquaOrDarkAqua isEqualToString:NSAppearanceNameDarkAqua];
+}
+
 nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
   NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
 
@@ -355,9 +396,6 @@ nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
     case IntID::CaretWidth:
       aResult = 1;
       break;
-    case IntID::ShowCaretDuringSelection:
-      aResult = 0;
-      break;
     case IntID::SelectTextfieldsOnKeyFocus:
       // Select textfield content when focused by kbd
       // used by EventStateManager::sTextfieldSelectModel
@@ -412,7 +450,12 @@ nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
       aResult = nsCocoaFeatures::OnBigSurOrLater();
       break;
     case IntID::MacRTL:
-      aResult = IsSystemOrientationRTL();
+      EnsureInit();
+      aResult = mRtl;
+      break;
+    case IntID::MacTitlebarHeight:
+      EnsureInit();
+      aResult = mTitlebarHeight;
       break;
     case IntID::AlertNotificationOrigin:
       aResult = NS_ALERT_TOP;
@@ -469,14 +512,6 @@ nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
       aResult = NSWorkspace.sharedWorkspace
                     .accessibilityDisplayShouldIncreaseContrast;
       break;
-    case IntID::VideoDynamicRange: {
-      // If the platform says it supports HDR, then we claim to support
-      // video-dynamic-range.
-      gfxPlatform* platform = gfxPlatform::GetPlatform();
-      MOZ_ASSERT(platform);
-      aResult = platform->SupportsHDR();
-      break;
-    }
     case IntID::PanelAnimations:
       aResult = 1;
       break;
@@ -519,28 +554,6 @@ nsresult nsLookAndFeel::NativeGetFloat(FloatID aID, float& aResult) {
   NS_OBJC_END_TRY_BLOCK_RETURN(NS_ERROR_FAILURE);
 }
 
-bool nsLookAndFeel::SystemWantsDarkTheme() {
-  // This returns true if the macOS system appearance is set to dark mode, false
-  // otherwise.
-  NSAppearanceName aquaOrDarkAqua =
-      [NSApp.effectiveAppearance bestMatchFromAppearancesWithNames:@[
-        NSAppearanceNameAqua, NSAppearanceNameDarkAqua
-      ]];
-  return [aquaOrDarkAqua isEqualToString:NSAppearanceNameDarkAqua];
-}
-
-/*static*/
-bool nsLookAndFeel::IsSystemOrientationRTL() {
-  NSWindow* window =
-      [[NSWindow alloc] initWithContentRect:NSZeroRect
-                                  styleMask:NSWindowStyleMaskBorderless
-                                    backing:NSBackingStoreBuffered
-                                      defer:NO];
-  auto direction = window.windowTitlebarLayoutDirection;
-  [window release];
-  return direction == NSUserInterfaceLayoutDirectionRightToLeft;
-}
-
 bool nsLookAndFeel::NativeGetFont(FontID aID, nsString& aFontName,
                                   gfxFontStyle& aFontStyle) {
   NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
diff --git a/widget/cocoa/nsNativeThemeCocoa.h b/widget/cocoa/nsNativeThemeCocoa.h
index 9488e50e1e..ebbf782264 100644
--- a/widget/cocoa/nsNativeThemeCocoa.h
+++ b/widget/cocoa/nsNativeThemeCocoa.h
@@ -159,7 +159,6 @@ class nsNativeThemeCocoa : public mozilla::widget::ThemeCocoa {
     eSpinButtonDown,  // SpinButtonParams
     eSegment,         // SegmentParams
     eSeparator,
-    eToolbar,    // bool
     eStatusBar,  // bool
     eGroupBox,
     eTextField,           // TextFieldParams
@@ -204,9 +203,6 @@ class nsNativeThemeCocoa : public mozilla::widget::ThemeCocoa {
     static WidgetInfo Separator() {
       return WidgetInfo(Widget::eSeparator, false);
     }
-    static WidgetInfo Toolbar(bool aParams) {
-      return WidgetInfo(Widget::eToolbar, aParams);
-    }
     static WidgetInfo StatusBar(bool aParams) {
       return WidgetInfo(Widget::eStatusBar, aParams);
     }
diff --git a/widget/cocoa/nsNativeThemeCocoa.mm b/widget/cocoa/nsNativeThemeCocoa.mm
index ff715ac57c..18913facea 100644
--- a/widget/cocoa/nsNativeThemeCocoa.mm
+++ b/widget/cocoa/nsNativeThemeCocoa.mm
@@ -399,9 +399,8 @@ static BOOL FrameIsInActiveWindow(nsIFrame* aFrame) {
 
 // Toolbar controls and content controls respond to different window
 // activeness states.
-static BOOL IsActive(nsIFrame* aFrame, BOOL aIsToolbarControl) {
-  if (aIsToolbarControl) return [NativeWindowForFrame(aFrame) isMainWindow];
-  return FrameIsInActiveWindow(aFrame);
+static BOOL IsActiveToolbarControl(nsIFrame* aFrame) {
+  return NativeWindowForFrame(aFrame).isMainWindow;
 }
 
 NS_IMPL_ISUPPORTS_INHERITED(nsNativeThemeCocoa, nsNativeTheme, nsITheme)
@@ -1021,7 +1020,6 @@ static bool IsToolbarStyleContainer(nsIFrame* aFrame) {
   }
 
   switch (aFrame->StyleDisplay()->EffectiveAppearance()) {
-    case StyleAppearance::Toolbar:
     case StyleAppearance::Statusbar:
       return true;
     default:
@@ -2078,35 +2076,6 @@ void nsNativeThemeCocoa::DrawSegment(CGContextRef cgContext,
   RenderWithCoreUI(drawRect, cgContext, dict);
 }
 
-void nsNativeThemeCocoa::DrawToolbar(CGContextRef cgContext,
-                                     const CGRect& inBoxRect, bool aIsMain) {
-  CGRect drawRect = inBoxRect;
-
-  // top border
-  drawRect.size.height = 1.0f;
-  DrawNativeGreyColorInRect(cgContext, toolbarTopBorderGrey, drawRect, aIsMain);
-
-  // background
-  drawRect.origin.y += drawRect.size.height;
-  drawRect.size.height = inBoxRect.size.height - 2.0f;
-  DrawNativeGreyColorInRect(cgContext, toolbarFillGrey, drawRect, aIsMain);
-
-  // bottom border
-  drawRect.origin.y += drawRect.size.height;
-  drawRect.size.height = 1.0f;
-  DrawNativeGreyColorInRect(cgContext, toolbarBottomBorderGrey, drawRect,
-                            aIsMain);
-}
-
-static bool ToolbarCanBeUnified(const gfx::Rect& aRect, NSWindow* aWindow) {
-  if (![aWindow isKindOfClass:[ToolbarWindow class]]) return false;
-
-  ToolbarWindow* win = (ToolbarWindow*)aWindow;
-  float unifiedToolbarHeight = [win unifiedToolbarHeight];
-  return aRect.X() == 0 && aRect.Width() >= [win frame].size.width &&
-         aRect.YMost() <= unifiedToolbarHeight;
-}
-
 void nsNativeThemeCocoa::DrawStatusBar(CGContextRef cgContext,
                                        const HIRect& inBoxRect, bool aIsMain) {
   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
@@ -2329,25 +2298,12 @@ Maybe<nsNativeThemeCocoa::WidgetInfo> nsNativeThemeCocoa::ComputeWidgetInfo(
     case StyleAppearance::Separator:
       return Some(WidgetInfo::Separator());
 
-    case StyleAppearance::Toolbar: {
-      NSWindow* win = NativeWindowForFrame(aFrame);
-      bool isMain = [win isMainWindow];
-      if (ToolbarCanBeUnified(nativeWidgetRect, win)) {
-        // Unified toolbars are drawn similar to vibrancy; we communicate their
-        // extents via the theme geometry mechanism and then place native views
-        // under Gecko's rendering. So Gecko just needs to be transparent in the
-        // place where the toolbar should be visible.
-        return Nothing();
-      }
-      return Some(WidgetInfo::Toolbar(isMain));
-    }
-
     case StyleAppearance::MozWindowTitlebar: {
       return Nothing();
     }
 
     case StyleAppearance::Statusbar:
-      return Some(WidgetInfo::StatusBar(IsActive(aFrame, YES)));
+      return Some(WidgetInfo::StatusBar(IsActiveToolbarControl(aFrame)));
 
     case StyleAppearance::MenulistButton:
     case StyleAppearance::Menulist: {
@@ -2594,11 +2550,6 @@ void nsNativeThemeCocoa::RenderWidget(const WidgetInfo& aWidgetInfo,
           HIThemeDrawSeparator(&macRect, &sdi, cgContext, HITHEME_ORIENTATION);
           break;
         }
-        case Widget::eToolbar: {
-          bool isMain = aWidgetInfo.Params<bool>();
-          DrawToolbar(cgContext, macRect, isMain);
-          break;
-        }
         case Widget::eStatusBar: {
           bool isMain = aWidgetInfo.Params<bool>();
           DrawStatusBar(cgContext, macRect, isMain);
@@ -2710,7 +2661,6 @@ bool nsNativeThemeCocoa::CreateWebRenderCommandsForWidget(
     case StyleAppearance::SpinnerDownbutton:
     case StyleAppearance::Toolbarbutton:
     case StyleAppearance::Separator:
-    case StyleAppearance::Toolbar:
     case StyleAppearance::MozWindowTitlebar:
     case StyleAppearance::Statusbar:
     case StyleAppearance::Menulist:
@@ -3091,8 +3041,6 @@ nsNativeThemeCocoa::WidgetStateChanged(nsIFrame* aFrame,
   // Some widget types just never change state.
   switch (aAppearance) {
     case StyleAppearance::MozWindowTitlebar:
-    case StyleAppearance::Toolbox:
-    case StyleAppearance::Toolbar:
     case StyleAppearance::Statusbar:
     case StyleAppearance::Tooltip:
     case StyleAppearance::Tabpanels:
@@ -3178,13 +3126,11 @@ bool nsNativeThemeCocoa::ThemeSupportsWidget(nsPresContext* aPresContext,
     case StyleAppearance::Spinner:
     case StyleAppearance::SpinnerUpbutton:
     case StyleAppearance::SpinnerDownbutton:
-    case StyleAppearance::Toolbar:
     case StyleAppearance::Statusbar:
     case StyleAppearance::NumberInput:
     case StyleAppearance::Textfield:
     case StyleAppearance::Textarea:
     case StyleAppearance::Searchfield:
-    case StyleAppearance::Toolbox:
     case StyleAppearance::ProgressBar:
     case StyleAppearance::Progresschunk:
     case StyleAppearance::Meter:
@@ -3265,7 +3211,6 @@ bool nsNativeThemeCocoa::WidgetAppearanceDependsOnWindowFocus(
     case StyleAppearance::SpinnerUpbutton:
     case StyleAppearance::SpinnerDownbutton:
     case StyleAppearance::Separator:
-    case StyleAppearance::Toolbox:
     case StyleAppearance::NumberInput:
     case StyleAppearance::Textfield:
     case StyleAppearance::Treeview:
@@ -3283,16 +3228,8 @@ nsITheme::ThemeGeometryType nsNativeThemeCocoa::ThemeGeometryTypeForWidget(
   switch (aAppearance) {
     case StyleAppearance::MozWindowTitlebar:
       return eThemeGeometryTypeTitlebar;
-    case StyleAppearance::Toolbar:
-      return eThemeGeometryTypeToolbar;
-    case StyleAppearance::Toolbox:
-      return eThemeGeometryTypeToolbox;
     case StyleAppearance::MozWindowButtonBox:
       return eThemeGeometryTypeWindowButtons;
-    case StyleAppearance::Tooltip:
-      return eThemeGeometryTypeTooltip;
-    case StyleAppearance::Menupopup:
-      return eThemeGeometryTypeMenu;
     default:
       return eThemeGeometryTypeUnknown;
   }
@@ -3307,7 +3244,6 @@ nsITheme::Transparency nsNativeThemeCocoa::GetWidgetTransparency(
   switch (aAppearance) {
     case StyleAppearance::Menupopup:
     case StyleAppearance::Tooltip:
-    case StyleAppearance::Toolbar:
       return eTransparent;
     case StyleAppearance::MozMacUnifiedToolbarWindow:
       // We want these to be treated as opaque by Gecko. We ensure there's an
diff --git a/widget/cocoa/nsNativeThemeColors.h b/widget/cocoa/nsNativeThemeColors.h
index 02ec96f51a..051335e9bc 100644
--- a/widget/cocoa/nsNativeThemeColors.h
+++ b/widget/cocoa/nsNativeThemeColors.h
@@ -10,43 +10,6 @@
 
 #include "mozilla/ColorScheme.h"
 
-enum ColorName {
-  toolbarTopBorderGrey,
-  toolbarFillGrey,
-  toolbarBottomBorderGrey,
-};
-
-static const int sLionThemeColors[][2] = {
-    /* { active window, inactive window } */
-    // toolbar:
-    {0xD0, 0xF0},  // top separator line
-    {0xB2, 0xE1},  // fill color
-    {0x59, 0x87},  // bottom separator line
-};
-
-static const int sYosemiteThemeColors[][2] = {
-    /* { active window, inactive window } */
-    // toolbar:
-    {0xBD, 0xDF},  // top separator line
-    {0xD3, 0xF6},  // fill color
-    {0xB3, 0xD1},  // bottom separator line
-};
-
-inline int NativeGreyColorAsInt(ColorName name, BOOL isMain) {
-  return sYosemiteThemeColors[name][isMain ? 0 : 1];
-}
-
-inline float NativeGreyColorAsFloat(ColorName name, BOOL isMain) {
-  return NativeGreyColorAsInt(name, isMain) / 255.0f;
-}
-
-inline void DrawNativeGreyColorInRect(CGContextRef context, ColorName name,
-                                      CGRect rect, BOOL isMain) {
-  float grey = NativeGreyColorAsFloat(name, isMain);
-  CGContextSetRGBFillColor(context, grey, grey, grey, 1.0f);
-  CGContextFillRect(context, rect);
-}
-
 inline NSAppearance* NSAppearanceForColorScheme(mozilla::ColorScheme aScheme) {
   NSAppearanceName appearanceName = aScheme == mozilla::ColorScheme::Light
                                         ? NSAppearanceNameAqua
diff --git a/widget/cocoa/nsPIWidgetCocoa.idl b/widget/cocoa/nsPIWidgetCocoa.idl
deleted file mode 100644
index 54aa0d5113..0000000000
--- a/widget/cocoa/nsPIWidgetCocoa.idl
+++ /dev/null
@@ -1,37 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsISupports.idl"
-
-interface nsIWidget;
-
-[ptr] native NSWindowPtr(NSWindow);
-
-//
-// nsPIWidgetCocoa
-//
-// A private interface (unfrozen, private to the widget implementation) that
-// gives us access to some extra features on a widget/window.
-//
-[uuid(f75ff69e-3a51-419e-bd29-042f804bc2ed)]
-interface nsPIWidgetCocoa : nsISupports
-{
-  void SendSetZLevelEvent();
-
-  // Find the displayed child sheet (if aShown) or a child sheet that
-  // wants to be displayed (if !aShown)
-  nsIWidget GetChildSheet(in boolean aShown);
-
-  // Get the parent widget (if any) StandardCreate() was called with.
-  nsIWidget GetRealParent();
-
-  // If the object implementing this interface is a sheet, this will return the
-  // native NSWindow it is attached to
-  readonly attribute NSWindowPtr sheetWindowParent;
-
-  // True if window is a sheet
-  readonly attribute boolean isSheet;
-
-}; // nsPIWidgetCocoa
diff --git a/widget/cocoa/nsWindowMap.mm b/widget/cocoa/nsWindowMap.mm
index d93f89cb58..6f92adceaf 100644
--- a/widget/cocoa/nsWindowMap.mm
+++ b/widget/cocoa/nsWindowMap.mm
@@ -115,31 +115,31 @@
   NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
 
   if ((self = [super init])) {
-    [[NSNotificationCenter defaultCenter]
+    [NSNotificationCenter.defaultCenter
         addObserver:self
            selector:@selector(windowBecameKey:)
                name:NSWindowDidBecomeKeyNotification
              object:inWindow];
 
-    [[NSNotificationCenter defaultCenter]
+    [NSNotificationCenter.defaultCenter
         addObserver:self
            selector:@selector(windowResignedKey:)
                name:NSWindowDidResignKeyNotification
              object:inWindow];
 
-    [[NSNotificationCenter defaultCenter]
+    [NSNotificationCenter.defaultCenter
         addObserver:self
            selector:@selector(windowBecameMain:)
                name:NSWindowDidBecomeMainNotification
              object:inWindow];
 
-    [[NSNotificationCenter defaultCenter]
+    [NSNotificationCenter.defaultCenter
         addObserver:self
            selector:@selector(windowResignedMain:)
                name:NSWindowDidResignMainNotification
              object:inWindow];
 
-    [[NSNotificationCenter defaultCenter]
+    [NSNotificationCenter.defaultCenter
         addObserver:self
            selector:@selector(windowWillClose:)
                name:NSWindowWillCloseNotification
@@ -153,7 +153,7 @@
 - (void)dealloc {
   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
 
-  [[NSNotificationCenter defaultCenter] removeObserver:self];
+  [NSNotificationCenter.defaultCenter removeObserver:self];
   [super dealloc];
 
   NS_OBJC_END_TRY_IGNORE_BLOCK;
@@ -171,7 +171,7 @@
 + (void)activateInWindow:(NSWindow*)aWindow {
   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
 
-  WindowDelegate* delegate = (WindowDelegate*)[aWindow delegate];
+  WindowDelegate* delegate = (WindowDelegate*)aWindow.delegate;
   if (!delegate || ![delegate isKindOfClass:[WindowDelegate class]]) return;
 
   if ([delegate toplevelActiveState]) return;
@@ -191,7 +191,7 @@
 + (void)deactivateInWindow:(NSWindow*)aWindow {
   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
 
-  WindowDelegate* delegate = (WindowDelegate*)[aWindow delegate];
+  WindowDelegate* delegate = (WindowDelegate*)aWindow.delegate;
   if (!delegate || ![delegate isKindOfClass:[WindowDelegate class]]) return;
 
   if (![delegate toplevelActiveState]) return;
@@ -205,9 +205,10 @@
 + (void)activateInWindowViews:(NSWindow*)aWindow {
   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
 
-  id firstResponder = [aWindow firstResponder];
-  if ([firstResponder isKindOfClass:[ChildView class]])
+  id firstResponder = aWindow.firstResponder;
+  if ([firstResponder isKindOfClass:[ChildView class]]) {
     [firstResponder viewsWindowDidBecomeKey];
+  }
 
   NS_OBJC_END_TRY_IGNORE_BLOCK;
 }
@@ -217,9 +218,10 @@
 + (void)deactivateInWindowViews:(NSWindow*)aWindow {
   NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
 
-  id firstResponder = [aWindow firstResponder];
-  if ([firstResponder isKindOfClass:[ChildView class]])
+  id firstResponder = aWindow.firstResponder;
+  if ([firstResponder isKindOfClass:[ChildView class]]) {
     [firstResponder viewsWindowDidResignKey];
+  }
 
   NS_OBJC_END_TRY_IGNORE_BLOCK;
 }
@@ -230,23 +232,23 @@
 // should be sent when a native window becomes key, and the NS_DEACTIVATE
 // event should be sent when it resignes key.
 - (void)windowBecameKey:(NSNotification*)inNotification {
-  NSWindow* window = (NSWindow*)[inNotification object];
+  NSWindow* window = inNotification.object;
 
-  id delegate = [window delegate];
+  id delegate = window.delegate;
   if (!delegate || ![delegate isKindOfClass:[WindowDelegate class]]) {
     [TopLevelWindowData activateInWindowViews:window];
-  } else if ([window isSheet] || [NSApp modalWindow]) {
+  } else if (window.isSheet || NSApp.modalWindow) {
     [TopLevelWindowData activateInWindow:window];
   }
 }
 
 - (void)windowResignedKey:(NSNotification*)inNotification {
-  NSWindow* window = (NSWindow*)[inNotification object];
+  NSWindow* window = inNotification.object;
 
-  id delegate = [window delegate];
+  id delegate = window.delegate;
   if (!delegate || ![delegate isKindOfClass:[WindowDelegate class]]) {
     [TopLevelWindowData deactivateInWindowViews:window];
-  } else if ([window isSheet] || [NSApp modalWindow]) {
+  } else if (window.isSheet || NSApp.modalWindow) {
     [TopLevelWindowData deactivateInWindow:window];
   }
 }
@@ -255,24 +257,24 @@
 // state).  So (for non-embedders) we need to ensure that a top-level window
 // is main when an NS_ACTIVATE event is sent to Gecko for it.
 - (void)windowBecameMain:(NSNotification*)inNotification {
-  NSWindow* window = (NSWindow*)[inNotification object];
-
-  id delegate = [window delegate];
+  NSWindow* window = inNotification.object;
+  id delegate = window.delegate;
   // Don't send events to a top-level window that has a sheet/modal-window open
   // above it -- as far as Gecko is concerned, it's inactive, and stays so until
   // the sheet/modal-window closes.
   if (delegate && [delegate isKindOfClass:[WindowDelegate class]] &&
-      ![window attachedSheet] && ![NSApp modalWindow])
+      !window.attachedSheet && !NSApp.modalWindow) {
     [TopLevelWindowData activateInWindow:window];
+  }
 }
 
 - (void)windowResignedMain:(NSNotification*)inNotification {
-  NSWindow* window = (NSWindow*)[inNotification object];
-
-  id delegate = [window delegate];
+  NSWindow* window = inNotification.object;
+  id delegate = window.delegate;
   if (delegate && [delegate isKindOfClass:[WindowDelegate class]] &&
-      ![window attachedSheet] && ![NSApp modalWindow])
+      ![window attachedSheet] && ![NSApp modalWindow]) {
     [TopLevelWindowData deactivateInWindow:window];
+  }
 }
 
 - (void)windowWillClose:(NSNotification*)inNotification {
diff --git a/widget/gtk/CompositorWidgetChild.cpp b/widget/gtk/CompositorWidgetChild.cpp
index b7908a43d4..3b6af872ed 100644
--- a/widget/gtk/CompositorWidgetChild.cpp
+++ b/widget/gtk/CompositorWidgetChild.cpp
@@ -38,13 +38,13 @@ void CompositorWidgetChild::NotifyClientSizeChanged(
   Unused << SendNotifyClientSizeChanged(aClientSize);
 }
 
-void CompositorWidgetChild::DisableRendering() {
-  Unused << SendDisableRendering();
+void CompositorWidgetChild::CleanupResources() {
+  Unused << SendCleanupResources();
 }
 
-void CompositorWidgetChild::EnableRendering(const uintptr_t aXWindow,
-                                            const bool aShaped) {
-  Unused << SendEnableRendering(aXWindow, aShaped);
+void CompositorWidgetChild::SetRenderingSurface(const uintptr_t aXWindow,
+                                                const bool aShaped) {
+  Unused << SendSetRenderingSurface(aXWindow, aShaped);
 }
 
 }  // namespace widget
diff --git a/widget/gtk/CompositorWidgetChild.h b/widget/gtk/CompositorWidgetChild.h
index b1cad75da3..f46cf63bfb 100644
--- a/widget/gtk/CompositorWidgetChild.h
+++ b/widget/gtk/CompositorWidgetChild.h
@@ -27,8 +27,9 @@ class CompositorWidgetChild final : public PCompositorWidgetChild,
   mozilla::ipc::IPCResult RecvUnobserveVsync() override;
 
   void NotifyClientSizeChanged(const LayoutDeviceIntSize& aClientSize) override;
-  void DisableRendering() override;
-  void EnableRendering(const uintptr_t aXWindow, const bool aShaped) override;
+  void CleanupResources() override;
+  void SetRenderingSurface(const uintptr_t aXWindow,
+                           const bool aShaped) override;
 
  private:
   RefPtr<CompositorVsyncDispatcher> mVsyncDispatcher;
diff --git a/widget/gtk/CompositorWidgetParent.cpp b/widget/gtk/CompositorWidgetParent.cpp
index 998614622e..7f576f35e7 100644
--- a/widget/gtk/CompositorWidgetParent.cpp
+++ b/widget/gtk/CompositorWidgetParent.cpp
@@ -40,14 +40,14 @@ mozilla::ipc::IPCResult CompositorWidgetParent::RecvNotifyClientSizeChanged(
   return IPC_OK();
 }
 
-mozilla::ipc::IPCResult CompositorWidgetParent::RecvDisableRendering() {
-  DisableRendering();
+mozilla::ipc::IPCResult CompositorWidgetParent::RecvCleanupResources() {
+  CleanupResources();
   return IPC_OK();
 }
 
-mozilla::ipc::IPCResult CompositorWidgetParent::RecvEnableRendering(
+mozilla::ipc::IPCResult CompositorWidgetParent::RecvSetRenderingSurface(
     const uintptr_t& aXWindow, const bool& aShaped) {
-  EnableRendering(aXWindow, aShaped);
+  SetRenderingSurface(aXWindow, aShaped);
   return IPC_OK();
 }
 
diff --git a/widget/gtk/CompositorWidgetParent.h b/widget/gtk/CompositorWidgetParent.h
index 2bbc70af3e..8c0a6e8c26 100644
--- a/widget/gtk/CompositorWidgetParent.h
+++ b/widget/gtk/CompositorWidgetParent.h
@@ -28,9 +28,9 @@ class CompositorWidgetParent final : public PCompositorWidgetParent,
   mozilla::ipc::IPCResult RecvNotifyClientSizeChanged(
       const LayoutDeviceIntSize& aClientSize) override;
 
-  mozilla::ipc::IPCResult RecvDisableRendering() override;
-  mozilla::ipc::IPCResult RecvEnableRendering(const uintptr_t& aXWindow,
-                                              const bool& aShaped) override;
+  mozilla::ipc::IPCResult RecvCleanupResources() override;
+  mozilla::ipc::IPCResult RecvSetRenderingSurface(const uintptr_t& aXWindow,
+                                                  const bool& aShaped) override;
 
  private:
   RefPtr<VsyncObserver> mVsyncObserver;
diff --git a/widget/gtk/GtkCompositorWidget.cpp b/widget/gtk/GtkCompositorWidget.cpp
index 36559cfd54..073ad5248f 100644
--- a/widget/gtk/GtkCompositorWidget.cpp
+++ b/widget/gtk/GtkCompositorWidget.cpp
@@ -7,6 +7,7 @@
 
 #include "mozilla/gfx/gfxVars.h"
 #include "mozilla/layers/CompositorThread.h"
+#include "mozilla/WidgetUtilsGtk.h"
 #include "mozilla/widget/InProcessCompositorWidget.h"
 #include "mozilla/widget/PlatformWidgetTypes.h"
 #include "nsWindow.h"
@@ -40,25 +41,22 @@ GtkCompositorWidget::GtkCompositorWidget(
 #if defined(MOZ_X11)
   if (GdkIsX11Display()) {
     ConfigureX11Backend((Window)aInitData.XWindow(), aInitData.Shaped());
-    LOG("GtkCompositorWidget::GtkCompositorWidget() [%p] mXWindow %p "
-        "mIsRenderingSuspended %d\n",
-        (void*)mWidget.get(), (void*)aInitData.XWindow(),
-        !!mIsRenderingSuspended);
+    LOG("GtkCompositorWidget::GtkCompositorWidget() [%p] mXWindow %p\n",
+        (void*)mWidget.get(), (void*)aInitData.XWindow());
   }
 #endif
 #if defined(MOZ_WAYLAND)
   if (GdkIsWaylandDisplay()) {
     ConfigureWaylandBackend();
-    LOG("GtkCompositorWidget::GtkCompositorWidget() [%p] mWidget %p "
-        "mIsRenderingSuspended %d\n",
-        (void*)mWidget.get(), (void*)mWidget, !!mIsRenderingSuspended);
+    LOG("GtkCompositorWidget::GtkCompositorWidget() [%p] mWidget %p\n",
+        (void*)mWidget.get(), (void*)mWidget);
   }
 #endif
 }
 
 GtkCompositorWidget::~GtkCompositorWidget() {
   LOG("GtkCompositorWidget::~GtkCompositorWidget [%p]\n", (void*)mWidget.get());
-  DisableRendering();
+  CleanupResources();
   RefPtr<nsIWidget> widget = mWidget.forget();
   NS_ReleaseOnMainThread("GtkCompositorWidget::mWidget", widget.forget());
 }
@@ -169,57 +167,47 @@ GtkCompositorWidget::GetNativeLayerRoot() {
 }
 #endif
 
-void GtkCompositorWidget::DisableRendering() {
-  LOG("GtkCompositorWidget::DisableRendering [%p]\n", (void*)mWidget.get());
-  mIsRenderingSuspended = true;
+void GtkCompositorWidget::CleanupResources() {
+  LOG("GtkCompositorWidget::CleanupResources [%p]\n", (void*)mWidget.get());
   mProvider.CleanupResources();
 }
 
 #if defined(MOZ_WAYLAND)
-bool GtkCompositorWidget::ConfigureWaylandBackend() {
+void GtkCompositorWidget::ConfigureWaylandBackend() {
   mProvider.Initialize(this);
-  return true;
 }
 #endif
 
 #if defined(MOZ_X11)
-bool GtkCompositorWidget::ConfigureX11Backend(Window aXWindow, bool aShaped) {
+void GtkCompositorWidget::ConfigureX11Backend(Window aXWindow, bool aShaped) {
   // We don't have X window yet.
   if (!aXWindow) {
-    mIsRenderingSuspended = true;
-    return false;
+    mProvider.CleanupResources();
+    return;
   }
   // Initialize the window surface provider
-  return mProvider.Initialize(aXWindow, aShaped);
+  mProvider.Initialize(aXWindow, aShaped);
 }
 #endif
 
-void GtkCompositorWidget::EnableRendering(const uintptr_t aXWindow,
-                                          const bool aShaped) {
-  LOG("GtkCompositorWidget::EnableRendering() [%p]\n", mWidget.get());
+void GtkCompositorWidget::SetRenderingSurface(const uintptr_t aXWindow,
+                                              const bool aShaped) {
+  LOG("GtkCompositorWidget::SetRenderingSurface() [%p]\n", mWidget.get());
 
-  if (!mIsRenderingSuspended) {
-    LOG("  quit, mIsRenderingSuspended = false\n");
-    return;
-  }
 #if defined(MOZ_WAYLAND)
   if (GdkIsWaylandDisplay()) {
     LOG("  configure widget %p\n", mWidget.get());
-    if (!ConfigureWaylandBackend()) {
-      return;
-    }
+    ConfigureWaylandBackend();
   }
 #endif
 #if defined(MOZ_X11)
   if (GdkIsX11Display()) {
     LOG("  configure XWindow %p shaped %d\n", (void*)aXWindow, aShaped);
-    if (!ConfigureX11Backend((Window)aXWindow, aShaped)) {
-      return;
-    }
+    ConfigureX11Backend((Window)aXWindow, aShaped);
   }
 #endif
-  mIsRenderingSuspended = false;
 }
+
 #ifdef MOZ_LOGGING
 bool GtkCompositorWidget::IsPopup() {
   return mWidget ? mWidget->IsPopup() : false;
diff --git a/widget/gtk/GtkCompositorWidget.h b/widget/gtk/GtkCompositorWidget.h
index bde88bde6c..d4834247f1 100644
--- a/widget/gtk/GtkCompositorWidget.h
+++ b/widget/gtk/GtkCompositorWidget.h
@@ -28,9 +28,9 @@ class PlatformCompositorWidgetDelegate : public CompositorWidgetDelegate {
       const LayoutDeviceIntSize& aClientSize) = 0;
   virtual GtkCompositorWidget* AsGtkCompositorWidget() { return nullptr; };
 
-  virtual void DisableRendering() = 0;
-  virtual void EnableRendering(const uintptr_t aXWindow,
-                               const bool aShaped) = 0;
+  virtual void CleanupResources() = 0;
+  virtual void SetRenderingSurface(const uintptr_t aXWindow,
+                                   const bool aShaped) = 0;
 
   // CompositorWidgetDelegate Overrides
 
@@ -74,10 +74,11 @@ class GtkCompositorWidget : public CompositorWidget,
 
   // Suspend rendering of this remote widget and clear all resources.
   // Can be used when underlying window is hidden/unmapped.
-  void DisableRendering() override;
+  void CleanupResources() override;
 
   // Resume rendering with to given aXWindow (X11) or nsWindow (Wayland).
-  void EnableRendering(const uintptr_t aXWindow, const bool aShaped) override;
+  void SetRenderingSurface(const uintptr_t aXWindow,
+                           const bool aShaped) override;
 
   // If we fail to set window size (due to different screen scale or so)
   // we can't paint the frame by compositor.
@@ -90,11 +91,6 @@ class GtkCompositorWidget : public CompositorWidget,
   RefPtr<mozilla::layers::NativeLayerRoot> GetNativeLayerRoot() override;
 #endif
 
-  bool PreRender(WidgetRenderingContext* aContext) override {
-    return !mIsRenderingSuspended;
-  }
-  bool IsHidden() const override { return mIsRenderingSuspended; }
-
   // PlatformCompositorWidgetDelegate Overrides
 
   void NotifyClientSizeChanged(const LayoutDeviceIntSize& aClientSize) override;
@@ -102,10 +98,10 @@ class GtkCompositorWidget : public CompositorWidget,
 
  private:
 #if defined(MOZ_WAYLAND)
-  bool ConfigureWaylandBackend();
+  void ConfigureWaylandBackend();
 #endif
 #if defined(MOZ_X11)
-  bool ConfigureX11Backend(Window aXWindow, bool aShaped);
+  void ConfigureX11Backend(Window aXWindow, bool aShaped);
 #endif
 #ifdef MOZ_LOGGING
   bool IsPopup();
@@ -129,7 +125,6 @@ class GtkCompositorWidget : public CompositorWidget,
 #ifdef MOZ_WAYLAND
   RefPtr<mozilla::layers::NativeLayerRootWayland> mNativeLayerRoot;
 #endif
-  Atomic<bool> mIsRenderingSuspended{true};
 };
 
 }  // namespace widget
diff --git a/widget/gtk/MPRISServiceHandler.cpp b/widget/gtk/MPRISServiceHandler.cpp
index ae1ef8654d..847bf3d78d 100644
--- a/widget/gtk/MPRISServiceHandler.cpp
+++ b/widget/gtk/MPRISServiceHandler.cpp
@@ -439,10 +439,10 @@ const char* MPRISServiceHandler::DesktopEntry() const {
 bool MPRISServiceHandler::PressKey(dom::MediaControlKey aKey) const {
   MOZ_ASSERT(mInitialized);
   if (!IsMediaKeySupported(aKey)) {
-    LOGMPRIS("%s is not supported", ToMediaControlKeyStr(aKey));
+    LOGMPRIS("%s is not supported", dom::GetEnumString(aKey).get());
     return false;
   }
-  LOGMPRIS("Press %s", ToMediaControlKeyStr(aKey));
+  LOGMPRIS("Press %s", dom::GetEnumString(aKey).get());
   EmitEvent(aKey);
   return true;
 }
@@ -861,7 +861,7 @@ bool MPRISServiceHandler::EmitSupportedKeyChanged(dom::MediaControlKey aKey,
                                                   bool aSupported) const {
   auto it = gKeyProperty.find(aKey);
   if (it == gKeyProperty.end()) {
-    LOGMPRIS("No property for %s", ToMediaControlKeyStr(aKey));
+    LOGMPRIS("No property for %s", dom::GetEnumString(aKey).get());
     return false;
   }
 
diff --git a/widget/gtk/MozContainer.cpp b/widget/gtk/MozContainer.cpp
index 775ae0488f..446dc97a66 100644
--- a/widget/gtk/MozContainer.cpp
+++ b/widget/gtk/MozContainer.cpp
@@ -87,19 +87,18 @@ void moz_container_class_init(MozContainerClass* klass) {
     GtkObjectClass *object_class = GTK_OBJECT_CLASS (klass); */
   GtkWidgetClass* widget_class = GTK_WIDGET_CLASS(klass);
 
+  widget_class->map = moz_container_map;
   widget_class->realize = moz_container_realize;
   widget_class->unrealize = moz_container_unrealize;
   widget_class->destroy = moz_container_destroy;
 
 #ifdef MOZ_WAYLAND
   if (mozilla::widget::GdkIsWaylandDisplay()) {
-    widget_class->map = moz_container_wayland_map;
     widget_class->size_allocate = moz_container_wayland_size_allocate;
     widget_class->map_event = moz_container_wayland_map_event;
     widget_class->unmap = moz_container_wayland_unmap;
   } else {
 #endif
-    widget_class->map = moz_container_map;
     widget_class->size_allocate = moz_container_size_allocate;
     widget_class->unmap = moz_container_unmap;
 #ifdef MOZ_WAYLAND
@@ -130,6 +129,10 @@ void moz_container_map(GtkWidget* widget) {
   if (gtk_widget_get_has_window(widget)) {
     gdk_window_show(gtk_widget_get_window(widget));
   }
+
+  // Enable rendering to nsWindow/MozContainer
+  nsWindow* window = moz_container_get_nsWindow(MOZ_CONTAINER(widget));
+  window->OnMap();
 }
 
 void moz_container_unmap(GtkWidget* widget) {
@@ -138,9 +141,9 @@ void moz_container_unmap(GtkWidget* widget) {
   LOGCONTAINER(("moz_container_unmap() [%p]",
                 (void*)moz_container_get_nsWindow(MOZ_CONTAINER(widget))));
 
-  // Disable rendering to MozContainer before we unmap it.
+  // Disable rendering to nsWindow/MozContainer before we really unmap it.
   nsWindow* window = moz_container_get_nsWindow(MOZ_CONTAINER(widget));
-  window->DisableRendering();
+  window->OnUnmap();
 
   gtk_widget_set_mapped(widget, FALSE);
 
diff --git a/widget/gtk/MozContainerWayland.cpp b/widget/gtk/MozContainerWayland.cpp
index 8490f25599..39e8a48390 100644
--- a/widget/gtk/MozContainerWayland.cpp
+++ b/widget/gtk/MozContainerWayland.cpp
@@ -419,21 +419,6 @@ gboolean moz_container_wayland_map_event(GtkWidget* widget,
   return FALSE;
 }
 
-void moz_container_wayland_map(GtkWidget* widget) {
-  LOGCONTAINER("%s [%p]\n", __FUNCTION__,
-               (void*)moz_container_get_nsWindow(MOZ_CONTAINER(widget)));
-
-  g_return_if_fail(IS_MOZ_CONTAINER(widget));
-
-  // We need to mark MozContainer as mapped to make sure
-  // moz_container_wayland_unmap() is called on hide/withdraw.
-  gtk_widget_set_mapped(widget, TRUE);
-
-  if (gtk_widget_get_has_window(widget)) {
-    gdk_window_show(gtk_widget_get_window(widget));
-  }
-}
-
 void moz_container_wayland_size_allocate(GtkWidget* widget,
                                          GtkAllocation* allocation) {
   GtkAllocation tmp_allocation;
diff --git a/widget/gtk/PCompositorWidget.ipdl b/widget/gtk/PCompositorWidget.ipdl
index d554a33144..e083e8d4ef 100644
--- a/widget/gtk/PCompositorWidget.ipdl
+++ b/widget/gtk/PCompositorWidget.ipdl
@@ -22,8 +22,8 @@ parent:
   async __delete__();
 
   async NotifyClientSizeChanged(LayoutDeviceIntSize aClientSize);
-  async DisableRendering();
-  async EnableRendering(uintptr_t aXWindow, bool aShaped);
+  async CleanupResources();
+  async SetRenderingSurface(uintptr_t aXWindow, bool aShaped);
 
 child:
 
diff --git a/widget/gtk/ScreenHelperGTK.cpp b/widget/gtk/ScreenHelperGTK.cpp
index 60be234c60..313bf54b1e 100644
--- a/widget/gtk/ScreenHelperGTK.cpp
+++ b/widget/gtk/ScreenHelperGTK.cpp
@@ -269,7 +269,7 @@ static already_AddRefed<Screen> MakeScreenGtk(GdkScreen* aScreen,
       contentsScale.scale, defaultCssScale.scale, dpi, refreshRate);
   return MakeAndAddRef<Screen>(rect, availRect, pixelDepth, pixelDepth,
                                refreshRate, contentsScale, defaultCssScale, dpi,
-                               Screen::IsPseudoDisplay::No);
+                               Screen::IsPseudoDisplay::No, Screen::IsHDR::No);
 }
 
 void ScreenGetterGtk::RefreshScreens() {
diff --git a/widget/gtk/WindowSurfaceProvider.cpp b/widget/gtk/WindowSurfaceProvider.cpp
index 82f9029315..c8b2c5a7d6 100644
--- a/widget/gtk/WindowSurfaceProvider.cpp
+++ b/widget/gtk/WindowSurfaceProvider.cpp
@@ -11,6 +11,7 @@
 #include "mozilla/gfx/Logging.h"
 #include "mozilla/layers/LayersTypes.h"
 #include "nsWindow.h"
+#include "mozilla/ScopeExit.h"
 
 #ifdef MOZ_WAYLAND
 #  include "mozilla/StaticPrefs_widget.h"
@@ -129,13 +130,13 @@ RefPtr<WindowSurface> WindowSurfaceProvider::CreateWindowSurface() {
     // 2. XPutImage
 #  ifdef MOZ_HAVE_SHMIMAGE
     if (!mIsShaped && nsShmImage::UseShm()) {
-      LOG(("Drawing to Window 0x%lx will use MIT-SHM\n", mXWindow));
+      LOG(("Drawing to Window 0x%lx will use MIT-SHM\n", (Window)mXWindow));
       return MakeRefPtr<WindowSurfaceX11SHM>(DefaultXDisplay(), mXWindow,
                                              mXVisual, mXDepth);
     }
 #  endif  // MOZ_HAVE_SHMIMAGE
 
-    LOG(("Drawing to Window 0x%lx will use XPutImage\n", mXWindow));
+    LOG(("Drawing to Window 0x%lx will use XPutImage\n", (Window)mXWindow));
     return MakeRefPtr<WindowSurfaceX11Image>(DefaultXDisplay(), mXWindow,
                                              mXVisual, mXDepth, mIsShaped);
   }
@@ -143,6 +144,11 @@ RefPtr<WindowSurface> WindowSurfaceProvider::CreateWindowSurface() {
   MOZ_RELEASE_ASSERT(false);
 }
 
+// We need to ignore thread safety checks here. We need to hold mMutex
+// between StartRemoteDrawingInRegion()/EndRemoteDrawingInRegion() calls
+// which confuses it.
+MOZ_PUSH_IGNORE_THREAD_SAFETY
+
 already_AddRefed<gfx::DrawTarget>
 WindowSurfaceProvider::StartRemoteDrawingInRegion(
     const LayoutDeviceIntRegion& aInvalidRegion,
@@ -151,7 +157,13 @@ WindowSurfaceProvider::StartRemoteDrawingInRegion(
     return nullptr;
   }
 
-  MutexAutoLock lock(mMutex);
+  // We return a reference to mWindowSurface inside draw target so we need to
+  // hold the mutex untill EndRemoteDrawingInRegion() call where draw target
+  // is returned.
+  // If we return null dt, EndRemoteDrawingInRegion() won't be called to
+  // release mutex.
+  mMutex.Lock();
+  auto unlockMutex = MakeScopeExit([&] { mMutex.Unlock(); });
 
   if (!mWindowSurfaceValid) {
     mWindowSurface = nullptr;
@@ -178,12 +190,20 @@ WindowSurfaceProvider::StartRemoteDrawingInRegion(
     dt = mWindowSurface->Lock(aInvalidRegion);
   }
 #endif
+  if (dt) {
+    // We have valid dt, mutex will be released in EndRemoteDrawingInRegion().
+    unlockMutex.release();
+  }
+
   return dt.forget();
 }
 
 void WindowSurfaceProvider::EndRemoteDrawingInRegion(
     gfx::DrawTarget* aDrawTarget, const LayoutDeviceIntRegion& aInvalidRegion) {
-  MutexAutoLock lock(mMutex);
+  // Unlock mutex from StartRemoteDrawingInRegion().
+  mMutex.AssertCurrentThreadOwns();
+  auto unlockMutex = MakeScopeExit([&] { mMutex.Unlock(); });
+
   // Commit to mWindowSurface only if we have a valid one.
   if (!mWindowSurface || !mWindowSurfaceValid) {
     return;
@@ -218,5 +238,7 @@ void WindowSurfaceProvider::EndRemoteDrawingInRegion(
   mWindowSurface->Commit(aInvalidRegion);
 }
 
+MOZ_POP_THREAD_SAFETY
+
 }  // namespace widget
 }  // namespace mozilla
diff --git a/widget/gtk/WindowSurfaceProvider.h b/widget/gtk/WindowSurfaceProvider.h
index 6aaf50e2da..44a0d78ec6 100644
--- a/widget/gtk/WindowSurfaceProvider.h
+++ b/widget/gtk/WindowSurfaceProvider.h
@@ -81,7 +81,7 @@ class WindowSurfaceProvider final {
    */
   mozilla::Mutex mMutex MOZ_UNANNOTATED;
   // WindowSurface needs to be re-created as underlying window was changed.
-  mozilla::Atomic<bool> mWindowSurfaceValid;
+  bool mWindowSurfaceValid;
 #ifdef MOZ_WAYLAND
   RefPtr<nsWindow> mWidget;
   // WindowSurfaceProvider is owned by GtkCompositorWidget so we don't need
@@ -91,7 +91,12 @@ class WindowSurfaceProvider final {
 #ifdef MOZ_X11
   bool mIsShaped;
   int mXDepth;
-  Window mXWindow;
+  // Make mXWindow atomic to allow it read from different threads
+  // and make tsan happy.
+  // We don't care much about actual mXWindow value (it may be valid XWindow or
+  // nullptr) because we invalidate mXWindow at compositor/renderer thread
+  // before it's release in unmap handler.
+  Atomic<Window, Relaxed> mXWindow;
   Visual* mXVisual;
 #endif
 };
diff --git a/widget/gtk/nsDragService.cpp b/widget/gtk/nsDragService.cpp
index 0135f97a4e..f435cdf2a0 100644
--- a/widget/gtk/nsDragService.cpp
+++ b/widget/gtk/nsDragService.cpp
@@ -607,6 +607,14 @@ nsDragService::EndDragSession(bool aDoneDrag, uint32_t aKeyModifiers) {
   mTargetDragContextForRemote = nullptr;
   mTargetWindow = nullptr;
   mPendingWindow = nullptr;
+  mPendingDragContext = nullptr;
+  mPendingWindowPoint = {};
+  mScheduledTask = eDragTaskNone;
+  if (mTaskSource) {
+    g_source_remove(mTaskSource);
+    mTaskSource = 0;
+  }
+  mPendingTime = 0;
   mCachedDragContext = 0;
 
   return nsBaseDragService::EndDragSession(aDoneDrag, aKeyModifiers);
@@ -1208,19 +1216,57 @@ void nsDragService::TargetDataReceived(GtkWidget* aWidget,
   GdkAtom target = gtk_selection_data_get_target(aSelectionData);
   GUniquePtr<gchar> name(gdk_atom_name(target));
   nsDependentCString flavor(name.get());
-
   if (gtk_targets_include_uri(&target, 1)) {
-    GUniquePtr<gchar*> uris(gtk_selection_data_get_uris(aSelectionData));
+    // For the vnd.portal.filetransfer and vnd.portal.files we receive numeric
+    // id when it's a local file. The numeric id is then used by
+    // gtk_selection_data_get_uris implementation to get the actual file
+    // available in the flatpak environment.
+    //
+    // However due to GTK implementation also for example the uris like https
+    // are also provided by the vnd.portal.filetransfer target. In this case the
+    // call  gtk_selection_data_get_uris fails. This is a bug in the gtk.
+    // To workaround it we try to create the valid uri and only if we fail
+    // we try to use the gtk_selection_data_get_uris. We ignore the valid uris
+    // for the vnd.portal.file* targets.
+    // See: https://gitlab.gnome.org/GNOME/gtk/-/issues/6563
+    if (flavor.Equals(gPortalFile) || flavor.Equals(gPortalFileTransfer)) {
+      const guchar* data = gtk_selection_data_get_data(aSelectionData);
+      if (!data || data[0] == '\0') {
+        LOGDRAGSERVICE("  Empty data!\n");
+        return;
+      }
+      nsCOMPtr<nsIURI> sourceURI;
+      nsresult rv =
+          NS_NewURI(getter_AddRefs(sourceURI), (const gchar*)data, nullptr);
+      if (NS_FAILED(rv)) {
+        // We're unable to get the URI, we'll use the
+        // gtk_selection_data_get_uris to get the actual file location
+        // accessible from the Firefox runtime.
+        GUniquePtr<gchar*> uris(gtk_selection_data_get_uris(aSelectionData));
+        uris.swap(mTargetDragUris);
+      } else {
+        LOGDRAGSERVICE(
+            "  got valid uri for MIME %s - this is bug in GTK - expected "
+            "numeric value for portal, got %s\n",
+            flavor.get(), data);
+        return;
+      }
+
+    } else {
+      GUniquePtr<gchar*> uris(gtk_selection_data_get_uris(aSelectionData));
+      uris.swap(mTargetDragUris);
+    }
 #ifdef MOZ_LOGGING
     if (MOZ_LOG_TEST(gWidgetDragLog, mozilla::LogLevel::Debug)) {
-      gchar** uri = uris.get();
+      gchar** uri = mTargetDragUris.get();
       while (uri && *uri) {
         LOGDRAGSERVICE("  got uri %s, MIME %s", *uri, flavor.get());
         uri++;
       }
     }
+
 #endif
-    uris.swap(mTargetDragUris);
+
     if (mTargetDragUris) {
       mCachedUris.InsertOrUpdate(
           flavor, GUniquePtr<gchar*>(g_strdupv(mTargetDragUris.get())));
@@ -2557,6 +2603,7 @@ gboolean nsDragService::RunScheduledTask() {
     // Nothing more to do
     // Returning false removes the task source from the event loop.
     mTaskSource = 0;
+    mPendingDragContext = nullptr;
     return FALSE;
   }
 
diff --git a/widget/gtk/nsLookAndFeel.cpp b/widget/gtk/nsLookAndFeel.cpp
index 040d942cdf..8702c154d6 100644
--- a/widget/gtk/nsLookAndFeel.cpp
+++ b/widget/gtk/nsLookAndFeel.cpp
@@ -800,6 +800,7 @@ nsresult nsLookAndFeel::PerThemeData::GetColor(ColorID aID,
     case ColorID::SpellCheckerUnderline:
     case ColorID::Mark:
     case ColorID::Marktext:
+    case ColorID::MozAutofillBackground:
       aColor = GetStandinForNativeColor(
           aID, mIsDark ? ColorScheme::Dark : ColorScheme::Light);
       break;
@@ -863,9 +864,6 @@ nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
     case IntID::CaretWidth:
       aResult = 1;
       break;
-    case IntID::ShowCaretDuringSelection:
-      aResult = 0;
-      break;
     case IntID::SelectTextfieldsOnKeyFocus: {
       GtkSettings* settings;
       gboolean select_on_focus;
diff --git a/widget/gtk/nsNativeThemeGTK.cpp b/widget/gtk/nsNativeThemeGTK.cpp
index 16945349bb..78d4e925fe 100644
--- a/widget/gtk/nsNativeThemeGTK.cpp
+++ b/widget/gtk/nsNativeThemeGTK.cpp
@@ -167,9 +167,6 @@ bool nsNativeThemeGTK::GetGtkWidgetAndState(StyleAppearance aAppearance,
   ElementState elementState = GetContentState(aFrame, aAppearance);
   if (aState) {
     memset(aState, 0, sizeof(GtkWidgetState));
-
-    // For XUL checkboxes and radio buttons, the state of the parent
-    // determines our state.
     if (aWidgetFlags) {
       if (elementState.HasState(ElementState::CHECKED)) {
         *aWidgetFlags |= MOZ_GTK_WIDGET_CHECKED;
@@ -241,7 +238,8 @@ bool nsNativeThemeGTK::GetGtkWidgetAndState(StyleAppearance aAppearance,
         aAppearance == StyleAppearance::MozWindowButtonMinimize ||
         aAppearance == StyleAppearance::MozWindowButtonMaximize ||
         aAppearance == StyleAppearance::MozWindowButtonRestore) {
-      aState->backdrop = !nsWindow::GetTopLevelWindowActiveState(aFrame);
+      aState->backdrop = aFrame->PresContext()->Document()->State().HasState(
+          dom::DocumentState::WINDOW_INACTIVE);
     }
   }
 
@@ -884,11 +882,6 @@ LayoutDeviceIntMargin nsNativeThemeGTK::GetWidgetBorder(
   CSSIntMargin result;
   GtkTextDirection direction = GetTextDirection(aFrame);
   switch (aAppearance) {
-    case StyleAppearance::Toolbox:
-      // gtk has no toolbox equivalent.  So, although we map toolbox to
-      // gtk's 'toolbar' for purposes of painting the widget background,
-      // we don't use the toolbar border for toolbox.
-      break;
     case StyleAppearance::Dualbutton:
       // TOOLBAR_DUAL_BUTTON is an interesting case.  We want a border to draw
       // around the entire button + dropdown, and also an inner border if you're
@@ -1169,9 +1162,7 @@ nsNativeThemeGTK::WidgetStateChanged(nsIFrame* aFrame,
   }
 
   // Some widget types just never change state.
-  if (aAppearance == StyleAppearance::Toolbox ||
-      aAppearance == StyleAppearance::Toolbar ||
-      aAppearance == StyleAppearance::Progresschunk ||
+  if (aAppearance == StyleAppearance::Progresschunk ||
       aAppearance == StyleAppearance::ProgressBar ||
       aAppearance == StyleAppearance::Tooltip ||
       aAppearance == StyleAppearance::MozWindowDecorations) {
@@ -1244,7 +1235,6 @@ nsNativeThemeGTK::ThemeSupportsWidget(nsPresContext* aPresContext,
     case StyleAppearance::Button:
     case StyleAppearance::Radio:
     case StyleAppearance::Checkbox:
-    case StyleAppearance::Toolbox:  // N/A
     case StyleAppearance::Toolbarbutton:
     case StyleAppearance::Dualbutton:  // so we can override the border with 0
     case StyleAppearance::ToolbarbuttonDropdown:
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index e84044990c..0a78d0c8ec 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -187,8 +187,6 @@ static GdkCursor* get_gtk_cursor(nsCursor aCursor);
 /* callbacks from widgets */
 static gboolean expose_event_cb(GtkWidget* widget, cairo_t* cr);
 static gboolean configure_event_cb(GtkWidget* widget, GdkEventConfigure* event);
-static void widget_map_cb(GtkWidget* widget);
-static void widget_unmap_cb(GtkWidget* widget);
 static void size_allocate_cb(GtkWidget* widget, GtkAllocation* allocation);
 static void toplevel_window_size_allocate_cb(GtkWidget* widget,
                                              GtkAllocation* allocation);
@@ -392,11 +390,11 @@ static void GtkWindowSetTransientFor(GtkWindow* aWindow, GtkWindow* aParent) {
 
 nsWindow::nsWindow()
     : mTitlebarRectMutex("nsWindow::mTitlebarRectMutex"),
-      mDestroyMutex("nsWindow::mDestroyMutex"),
+      mWindowVisibilityMutex("nsWindow::mWindowVisibilityMutex"),
+      mIsMapped(false),
       mIsDestroyed(false),
       mIsShown(false),
       mNeedsShow(false),
-      mIsMapped(false),
       mEnabled(true),
       mCreated(false),
       mHandleTouchEvent(false),
@@ -581,7 +579,6 @@ void nsWindow::Destroy() {
 
   LOG("nsWindow::Destroy\n");
 
-  MutexAutoLock lock(mDestroyMutex);
   mIsDestroyed = true;
   mCreated = false;
 
@@ -612,6 +609,9 @@ void nsWindow::Destroy() {
 
   NativeShow(false);
 
+  MOZ_ASSERT(!gtk_widget_get_mapped(mShell));
+  MOZ_ASSERT(!gtk_widget_get_mapped(GTK_WIDGET(mContainer)));
+
   ClearTransparencyBitmap();
 
   DestroyLayerManager();
@@ -3165,23 +3165,34 @@ void nsWindow::SetFocus(Raise aRaise, mozilla::dom::CallerType aCallerType) {
   LOG("  widget now has focus in SetFocus()");
 }
 
+void nsWindow::ResetScreenBounds() {
+  mGdkWindowOrigin.reset();
+  mGdkWindowRootOrigin.reset();
+}
+
 LayoutDeviceIntRect nsWindow::GetScreenBounds() {
   if (!mGdkWindow) {
     return mBounds;
   }
 
   const LayoutDeviceIntPoint origin = [&] {
-    gint x, y;
-    gdk_window_get_root_origin(mGdkWindow, &x, &y);
+    GdkPoint origin;
+
+    if (mGdkWindowRootOrigin.isSome()) {
+      origin = mGdkWindowRootOrigin.value();
+    } else {
+      gdk_window_get_root_origin(mGdkWindow, &origin.x, &origin.y);
+      mGdkWindowRootOrigin = Some(origin);
+    }
 
     // Workaround for https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/4820
     // Bug 1775017 Gtk < 3.24.35 returns scaled values for
     // override redirected window on X11.
     if (gtk_check_version(3, 24, 35) != nullptr && GdkIsX11Display() &&
         gdk_window_get_window_type(mGdkWindow) == GDK_WINDOW_TEMP) {
-      return LayoutDeviceIntPoint(x, y);
+      return LayoutDeviceIntPoint(origin.x, origin.y);
     }
-    return GdkPointToDevicePixels({x, y});
+    return GdkPointToDevicePixels(origin);
   }();
 
   // mBounds.Size() is the window bounds, not the window-manager frame
@@ -3237,6 +3248,7 @@ void nsWindow::RecomputeClientOffset(bool aNotify) {
 gboolean nsWindow::OnPropertyNotifyEvent(GtkWidget* aWidget,
                                          GdkEventProperty* aEvent) {
   if (aEvent->atom == gdk_atom_intern("_NET_FRAME_EXTENTS", FALSE)) {
+    ResetScreenBounds();
     RecomputeClientOffset(/* aNotify = */ true);
     return FALSE;
   }
@@ -3395,40 +3407,37 @@ void* nsWindow::GetNativeData(uint32_t aDataType) {
     case NS_NATIVE_OPENGL_CONTEXT:
       return nullptr;
     case NS_NATIVE_EGL_WINDOW: {
+      // On X11 we call it:
+      // 1) If window is mapped on OnMap() by nsWindow::ResumeCompositorImpl(),
+      //    new EGLSurface/XWindow is created.
+      // 2) If window is hidden on OnUnmap(), we replace EGLSurface/XWindow
+      //    by offline surface and release XWindow.
+
+      // On Wayland it:
+      // 1) If window is mapped on OnMap(), we request frame callback
+      //    at MozContainer. If we get frame callback at MozContainer,
+      //    nsWindow::ResumeCompositorImpl() is called from it
+      //    and EGLSurface/wl_surface is created.
+      // 2) If window is hidden on OnUnmap(), we replace EGLSurface/wl_surface
+      //    by offline surface and release XWindow.
+
+      // If nsWindow is already destroyed, don't try to get EGL window at all,
+      // we're going to be deleted anyway.
+      MutexAutoLock lock(mWindowVisibilityMutex);
       void* eglWindow = nullptr;
-
-      // We can't block on mutex here as it leads to a deadlock:
-      // 1) mutex is taken at nsWindow::Destroy()
-      // 2) NS_NATIVE_EGL_WINDOW is called from compositor/rendering thread,
-      //    blocking on mutex.
-      // 3) DestroyCompositor() is called by nsWindow::Destroy(). As a sync
-      //    call it waits to compositor/rendering threads,
-      //    but they're blocked at 2).
-      //    It's fine if we return null EGL window during DestroyCompositor(),
-      //    in such case compositor painting is skipped.
-      if (mDestroyMutex.TryLock()) {
-        if (mGdkWindow && !mIsDestroyed) {
+      if (mIsMapped && !mIsDestroyed) {
 #ifdef MOZ_X11
-          if (GdkIsX11Display()) {
-            eglWindow = (void*)GDK_WINDOW_XID(mGdkWindow);
-          }
+        if (GdkIsX11Display()) {
+          eglWindow = (void*)GDK_WINDOW_XID(mGdkWindow);
+        }
 #endif
 #ifdef MOZ_WAYLAND
-          if (GdkIsWaylandDisplay()) {
-            bool hiddenWindow =
-                mCompositorWidgetDelegate &&
-                mCompositorWidgetDelegate->AsGtkCompositorWidget() &&
-                mCompositorWidgetDelegate->AsGtkCompositorWidget()->IsHidden();
-            if (!hiddenWindow) {
-              eglWindow = moz_container_wayland_get_egl_window(
-                  mContainer, FractionalScaleFactor());
-            }
-          }
-#endif
+        if (GdkIsWaylandDisplay()) {
+          eglWindow = moz_container_wayland_get_egl_window(
+              mContainer, FractionalScaleFactor());
         }
-        mDestroyMutex.Unlock();
+#endif
       }
-
       LOG("Get NS_NATIVE_EGL_WINDOW mGdkWindow %p returned eglWindow %p",
           mGdkWindow, eglWindow);
       return eglWindow;
@@ -3556,11 +3565,16 @@ LayoutDeviceIntPoint nsWindow::WidgetToScreenOffset() {
   if (IsWaylandPopup() && !mPopupUseMoveToRect) {
     return mBounds.TopLeft();
   }
-  nsIntPoint origin(0, 0);
-  if (mGdkWindow) {
-    gdk_window_get_origin(mGdkWindow, &origin.x.value, &origin.y.value);
+
+  GdkPoint origin{};
+  if (mGdkWindowOrigin.isSome()) {
+    origin = mGdkWindowOrigin.value();
+  } else if (mGdkWindow) {
+    gdk_window_get_origin(mGdkWindow, &origin.x, &origin.y);
+    mGdkWindowOrigin = Some(origin);
   }
-  return GdkPointToDevicePixels({origin.x, origin.y});
+
+  return GdkPointToDevicePixels(origin);
 }
 
 void nsWindow::CaptureRollupEvents(bool aDoCapture) {
@@ -3749,6 +3763,8 @@ void nsWindow::RequestRepaint(LayoutDeviceIntRegion& aRepaintRegion) {
   KnowsCompositor* knowsCompositor = renderer->AsKnowsCompositor();
 
   if (knowsCompositor && layerManager && mCompositorSession) {
+    LOG("nsWindow::RequestRepaint()");
+
     if (!mConfiguredClearColor && !IsPopup()) {
       layerManager->WrBridge()->SendSetDefaultClearColor(LookAndFeel::Color(
           LookAndFeel::ColorID::Window, PreferenceSheet::ColorSchemeForChrome(),
@@ -3764,9 +3780,13 @@ void nsWindow::RequestRepaint(LayoutDeviceIntRegion& aRepaintRegion) {
 }
 
 gboolean nsWindow::OnExposeEvent(cairo_t* cr) {
+  LOG("nsWindow::OnExposeEvent GdkWindow [%p] XID [0x%lx]", mGdkWindow,
+      GetX11Window());
+
   // This might destroy us.
   NotifyOcclusionState(OcclusionState::VISIBLE);
   if (mIsDestroyed) {
+    LOG("destroyed after NotifyOcclusionState()");
     return FALSE;
   }
 
@@ -3774,26 +3794,27 @@ gboolean nsWindow::OnExposeEvent(cairo_t* cr) {
   // May run event loop and destroy us.
   MaybeDispatchResized();
   if (mIsDestroyed) {
+    LOG("destroyed after MaybeDispatchResized()");
     return FALSE;
   }
 
   // Windows that are not visible will be painted after they become visible.
   if (!mGdkWindow || !mHasMappedToplevel) {
+    LOG("quit, !mGdkWindow || !mHasMappedToplevel");
     return FALSE;
   }
 #ifdef MOZ_WAYLAND
   if (GdkIsWaylandDisplay() && !moz_container_wayland_can_draw(mContainer)) {
+    LOG("quit, !moz_container_wayland_can_draw()");
     return FALSE;
   }
 #endif
 
   if (!GetListener()) {
+    LOG("quit, !GetListener()");
     return FALSE;
   }
 
-  LOG("nsWindow::OnExposeEvent GdkWindow [%p] XID [0x%lx]", mGdkWindow,
-      GetX11Window());
-
   LayoutDeviceIntRegion exposeRegion;
   if (!ExtractExposeRegion(exposeRegion, cr)) {
     LOG("  no rects, quit");
@@ -3816,19 +3837,24 @@ gboolean nsWindow::OnExposeEvent(cairo_t* cr) {
   // If the window has been destroyed during the will paint notification,
   // there is nothing left to do.
   if (!mGdkWindow || mIsDestroyed) {
+    LOG("quit, !mGdkWindow || mIsDestroyed");
     return TRUE;
   }
 
   // Re-get all rendering components since the will paint notification
   // might have killed it.
   nsIWidgetListener* listener = GetListener();
-  if (!listener) return FALSE;
+  if (!listener) {
+    LOG("quit, !listener");
+    return FALSE;
+  }
 
   WindowRenderer* renderer = GetWindowRenderer();
   WebRenderLayerManager* layerManager = renderer->AsWebRender();
   KnowsCompositor* knowsCompositor = renderer->AsKnowsCompositor();
 
   if (knowsCompositor && layerManager && layerManager->NeedsComposite()) {
+    LOG("needs composite, ScheduleComposite() call");
     layerManager->ScheduleComposite(wr::RenderReasons::WIDGET);
     layerManager->SetNeedsComposite(false);
   }
@@ -3859,11 +3885,13 @@ gboolean nsWindow::OnExposeEvent(cairo_t* cr) {
   }
 
   if (region.IsEmpty()) {
+    LOG("quit, region.IsEmpty()");
     return TRUE;
   }
 
   // If this widget uses OMTC...
   if (renderer->GetBackendType() == LayersBackend::LAYERS_WR) {
+    LOG("redirect painting to OMTC rendering...");
     listener->PaintWindow(this, region);
 
     // Re-get the listener since the will paint notification might have
@@ -4048,6 +4076,8 @@ gboolean nsWindow::OnConfigureEvent(GtkWidget* aWidget,
     mPendingConfigures--;
   }
 
+  ResetScreenBounds();
+
   // Don't fire configure event for scale changes, we handle that
   // OnScaleChanged event. Skip that for toplevel windows only.
   if (mGdkWindow && IsTopLevelWindowType()) {
@@ -4103,45 +4133,12 @@ gboolean nsWindow::OnConfigureEvent(GtkWidget* aWidget,
   return FALSE;
 }
 
-void nsWindow::OnMap() {
-  LOG("nsWindow::OnMap");
-  // Gtk mapped widget to screen. Configure underlying GdkWindow properly
-  // as our rendering target.
-  // This call means we have X11 (or Wayland) window we can render to by GL
-  // so we need to notify compositor about it.
-  mIsMapped = true;
-  ConfigureGdkWindow();
-}
-
-void nsWindow::OnUnmap() {
-  LOG("nsWindow::OnUnmap");
-
-  mIsMapped = false;
-
-  if (mSourceDragContext) {
-    static auto sGtkDragCancel =
-        (void (*)(GdkDragContext*))dlsym(RTLD_DEFAULT, "gtk_drag_cancel");
-    if (sGtkDragCancel) {
-      sGtkDragCancel(mSourceDragContext);
-      mSourceDragContext = nullptr;
-    }
-  }
-
-  // We don't have valid XWindow any more,
-  // so clear stored ones at GtkCompositorWidget() for OMTC rendering
-  // and mSurfaceProvider for legacy rendering.
-  if (GdkIsX11Display()) {
-    mSurfaceProvider.CleanupResources();
-    if (mCompositorWidgetDelegate) {
-      mCompositorWidgetDelegate->DisableRendering();
-    }
-  }
-}
-
 void nsWindow::OnSizeAllocate(GtkAllocation* aAllocation) {
   LOG("nsWindow::OnSizeAllocate %d,%d -> %d x %d\n", aAllocation->x,
       aAllocation->y, aAllocation->width, aAllocation->height);
 
+  ResetScreenBounds();
+
   // Client offset are updated by _NET_FRAME_EXTENTS on X11 when system titlebar
   // is enabled. In either cases (Wayland or system titlebar is off on X11)
   // we don't get _NET_FRAME_EXTENTS X11 property notification so we derive
@@ -4650,9 +4647,16 @@ bool nsWindow::DoTitlebarAction(LookAndFeel::TitlebarEvent aEvent,
       LOG("  action menu");
       TryToShowNativeWindowMenu(aButtonEvent);
       break;
-    // Lower is part of gtk_surface1 protocol which we can't support
-    // as Gtk keeps it private. So emulate it by minimize.
     case LookAndFeel::TitlebarAction::WindowLower:
+      LOG("  action lower");
+      // Lower is part of gtk_surface1 protocol which we can't support
+      // as Gtk keeps it private. So emulate it by minimize.
+      if (GdkIsWaylandDisplay()) {
+        SetSizeMode(nsSizeMode_Minimized);
+      } else {
+        gdk_window_lower(GetToplevelGdkWindow());
+      }
+      break;
     case LookAndFeel::TitlebarAction::WindowMinimize:
       LOG("  action minimize");
       SetSizeMode(nsSizeMode_Minimized);
@@ -5425,8 +5429,8 @@ void nsWindow::OnScaleChanged(bool aNotify) {
 
   NotifyAPZOfDPIChange();
 
-  LOG("OnScaleChanged %d, %f -> %d, %f\n", int(mCeiledScaleFactor),
-      mFractionalScaleFactor, newCeiled, newFractional);
+  LOG("OnScaleChanged %d, %f -> %d, %f Notify %d\n", int(mCeiledScaleFactor),
+      mFractionalScaleFactor, newCeiled, newFractional, aNotify);
 
   mCeiledScaleFactor = newCeiled;
   mFractionalScaleFactor = newFractional;
@@ -5822,8 +5826,8 @@ bool nsWindow::GetShapedState() {
 }
 
 void nsWindow::ConfigureCompositor() {
-  MOZ_DIAGNOSTIC_ASSERT(mCompositorState == COMPOSITOR_ENABLED);
   MOZ_DIAGNOSTIC_ASSERT(mIsMapped);
+  MOZ_DIAGNOSTIC_ASSERT(mCompositorState == COMPOSITOR_ENABLED);
 
   LOG("nsWindow::ConfigureCompositor()");
   auto startCompositing = [self = RefPtr{this}, this]() -> void {
@@ -5833,7 +5837,7 @@ void nsWindow::ConfigureCompositor() {
     // too late
     if (mIsDestroyed || !mIsMapped) {
       LOG("  quit, mIsDestroyed = %d mIsMapped = %d", !!mIsDestroyed,
-          mIsMapped);
+          !!mIsMapped);
       return;
     }
     // Compositor will be resumed later by ResumeCompositorFlickering().
@@ -5860,73 +5864,6 @@ void nsWindow::ConfigureCompositor() {
   }
 }
 
-void nsWindow::ConfigureGdkWindow() {
-  LOG("nsWindow::ConfigureGdkWindow()");
-
-  EnsureGdkWindow();
-  OnScaleChanged(/* aNotify = */ false);
-
-  if (mIsAlert) {
-    gdk_window_set_override_redirect(mGdkWindow, TRUE);
-  }
-
-#ifdef MOZ_X11
-  if (GdkIsX11Display()) {
-    mSurfaceProvider.Initialize(GetX11Window(), GetShapedState());
-
-    // Set window manager hint to keep fullscreen windows composited.
-    //
-    // If the window were to get unredirected, there could be visible
-    // tearing because Gecko does not align its framebuffer updates with
-    // vblank.
-    SetCompositorHint(GTK_WIDGET_COMPOSIDED_ENABLED);
-  }
-#endif
-#ifdef MOZ_WAYLAND
-  if (GdkIsWaylandDisplay()) {
-    mSurfaceProvider.Initialize(this);
-  }
-#endif
-
-  if (mIsDragPopup) {
-    if (GdkIsWaylandDisplay()) {
-      // Disable painting to the widget on Wayland as we paint directly to the
-      // widget. Wayland compositors does not paint wl_subsurface
-      // of D&D widget.
-      if (GtkWidget* parent = gtk_widget_get_parent(mShell)) {
-        GtkWidgetDisableUpdates(parent);
-      }
-      GtkWidgetDisableUpdates(mShell);
-      GtkWidgetDisableUpdates(GTK_WIDGET(mContainer));
-    } else {
-      // Disable rendering of parent container on X11 to avoid flickering.
-      if (GtkWidget* parent = gtk_widget_get_parent(mShell)) {
-        gtk_widget_set_opacity(parent, 0.0);
-      }
-    }
-  }
-
-  if (mWindowType == WindowType::Popup) {
-    if (mNoAutoHide) {
-      gint wmd = ConvertBorderStyles(mBorderStyle);
-      if (wmd != -1) {
-        gdk_window_set_decorations(mGdkWindow, (GdkWMDecoration)wmd);
-      }
-    }
-    // If the popup ignores mouse events, set an empty input shape.
-    SetInputRegion(mInputRegion);
-  }
-
-  RefreshWindowClass();
-
-  // We're not mapped yet but we have already created compositor.
-  if (mCompositorWidgetDelegate) {
-    ConfigureCompositor();
-  }
-
-  LOG("  finished, new GdkWindow %p XID 0x%lx\n", mGdkWindow, GetX11Window());
-}
-
 nsresult nsWindow::Create(nsIWidget* aParent, nsNativeWidget aNativeParent,
                           const LayoutDeviceIntRect& aRect,
                           widget::InitData* aInitData) {
@@ -6355,8 +6292,6 @@ nsresult nsWindow::Create(nsIWidget* aParent, nsNativeWidget aNativeParent,
                          G_CALLBACK(settings_xft_dpi_changed_cb), this);
 
   // Widget signals
-  g_signal_connect(mContainer, "map", G_CALLBACK(widget_map_cb), nullptr);
-  g_signal_connect(mContainer, "unmap", G_CALLBACK(widget_unmap_cb), nullptr);
   g_signal_connect_after(mContainer, "size_allocate",
                          G_CALLBACK(size_allocate_cb), nullptr);
   g_signal_connect(mContainer, "hierarchy-changed",
@@ -6567,6 +6502,10 @@ void nsWindow::NativeMoveResize(bool aMoved, bool aResized) {
   LOG("nsWindow::NativeMoveResize move %d resize %d to %d,%d -> %d x %d\n",
       aMoved, aResized, topLeft.x, topLeft.y, size.width, size.height);
 
+  if (aMoved) {
+    ResetScreenBounds();
+  }
+
   if (aResized && !AreBoundsSane()) {
     LOG("  bounds are insane, hidding the window");
     // We have been resized but to incorrect size.
@@ -6648,8 +6587,8 @@ void nsWindow::PauseCompositorFlickering() {
 
   CompositorBridgeChild* remoteRenderer = GetRemoteRenderer();
   if (remoteRenderer) {
-    remoteRenderer->SendPause();
     mCompositorState = COMPOSITOR_PAUSED_FLICKERING;
+    remoteRenderer->SendPause();
     mCompositorPauseTimeoutID = (int)g_timeout_add(
         COMPOSITOR_PAUSE_TIMEOUT,
         [](void* data) -> gint {
@@ -6703,7 +6642,8 @@ void nsWindow::ResumeCompositorImpl() {
   LOG("nsWindow::ResumeCompositorImpl()\n");
 
   MOZ_DIAGNOSTIC_ASSERT(mCompositorWidgetDelegate);
-  mCompositorWidgetDelegate->EnableRendering(GetX11Window(), GetShapedState());
+  mCompositorWidgetDelegate->SetRenderingSurface(GetX11Window(),
+                                                 GetShapedState());
 
   // As WaylandStartVsync needs mCompositorWidgetDelegate this is the right
   // time to start it.
@@ -8287,25 +8227,6 @@ static gboolean configure_event_cb(GtkWidget* widget,
   return window->OnConfigureEvent(widget, event);
 }
 
-// Some Gtk widget code may call gtk_widget_unrealize() which destroys
-// mGdkWindow. We need to listen on this signal and re-create
-// mGdkWindow when we're already mapped.
-static void widget_map_cb(GtkWidget* widget) {
-  RefPtr<nsWindow> window = get_window_for_gtk_widget(widget);
-  if (!window) {
-    return;
-  }
-  window->OnMap();
-}
-
-static void widget_unmap_cb(GtkWidget* widget) {
-  RefPtr<nsWindow> window = get_window_for_gtk_widget(widget);
-  if (!window) {
-    return;
-  }
-  window->OnUnmap();
-}
-
 static void size_allocate_cb(GtkWidget* widget, GtkAllocation* allocation) {
   RefPtr<nsWindow> window = get_window_for_gtk_widget(widget);
   if (!window) {
@@ -9124,7 +9045,7 @@ void nsWindow::DidGetNonBlankPaint() {
 void nsWindow::SetCompositorWidgetDelegate(CompositorWidgetDelegate* delegate) {
   LOG("nsWindow::SetCompositorWidgetDelegate %p mIsMapped %d "
       "mCompositorWidgetDelegate %p\n",
-      delegate, mIsMapped, mCompositorWidgetDelegate);
+      delegate, !!mIsMapped, mCompositorWidgetDelegate);
 
   MOZ_RELEASE_ASSERT(NS_IsMainThread());
   if (delegate) {
@@ -9962,26 +9883,6 @@ void nsWindow::UnlockNativePointer() {
 }
 #endif
 
-bool nsWindow::GetTopLevelWindowActiveState(nsIFrame* aFrame) {
-  // Used by window frame and button box rendering. We can end up in here in
-  // the content process when rendering one of these moz styles freely in a
-  // page. Fail in this case, there is no applicable window focus state.
-  if (!XRE_IsParentProcess()) {
-    return false;
-  }
-  // All headless windows are considered active so they are painted.
-  if (gfxPlatform::IsHeadless()) {
-    return true;
-  }
-  // Get the widget. nsIFrame's GetNearestWidget walks up the view chain
-  // until it finds a real window.
-  nsWindow* window = static_cast<nsWindow*>(aFrame->GetNearestWidget());
-  if (!window) {
-    return false;
-  }
-  return !window->mTitlebarBackdropState;
-}
-
 static nsIFrame* FindTitlebarFrame(nsIFrame* aFrame) {
   for (nsIFrame* childFrame : aFrame->PrincipalChildList()) {
     StyleAppearance appearance =
@@ -10072,41 +9973,34 @@ nsWindow* nsWindow::GetFocusedWindow() { return gFocusWindow; }
 #ifdef MOZ_WAYLAND
 bool nsWindow::SetEGLNativeWindowSize(
     const LayoutDeviceIntSize& aEGLWindowSize) {
-  if (!GdkIsWaylandDisplay()) {
+  if (!GdkIsWaylandDisplay() || !mIsMapped) {
     return true;
   }
 
-  // SetEGLNativeWindowSize() is called from renderer/compositor thread,
-  // make sure nsWindow is not destroyed.
-  bool paint = false;
+  if (mCompositorState == COMPOSITOR_PAUSED_FLICKERING) {
+    LOG("nsWindow::SetEGLNativeWindowSize() return, "
+        "COMPOSITOR_PAUSED_FLICKERING is set");
+    return false;
+  }
 
-  // See NS_NATIVE_EGL_WINDOW why we can't block here.
-  if (mDestroyMutex.TryLock()) {
-    if (!mIsDestroyed) {
-      gint scale = GdkCeiledScaleFactor();
+  gint scale = GdkCeiledScaleFactor();
 #  ifdef MOZ_LOGGING
-      if (LOG_ENABLED()) {
-        static uintptr_t lastSizeLog = 0;
-        uintptr_t sizeLog = uintptr_t(this) + aEGLWindowSize.width +
-                            aEGLWindowSize.height + scale +
-                            aEGLWindowSize.width / scale +
-                            aEGLWindowSize.height / scale;
-        if (lastSizeLog != sizeLog) {
-          lastSizeLog = sizeLog;
-          LOG("nsWindow::SetEGLNativeWindowSize() %d x %d scale %d (unscaled "
-              "%d x "
-              "%d)",
-              aEGLWindowSize.width, aEGLWindowSize.height, scale,
-              aEGLWindowSize.width / scale, aEGLWindowSize.height / scale);
-        }
-      }
-#  endif
-      paint = moz_container_wayland_egl_window_set_size(
-          mContainer, aEGLWindowSize.ToUnknownSize(), scale);
+  if (LOG_ENABLED()) {
+    static uintptr_t lastSizeLog = 0;
+    uintptr_t sizeLog =
+        uintptr_t(this) + aEGLWindowSize.width + aEGLWindowSize.height + scale +
+        aEGLWindowSize.width / scale + aEGLWindowSize.height / scale;
+    if (lastSizeLog != sizeLog) {
+      lastSizeLog = sizeLog;
+      LOG("nsWindow::SetEGLNativeWindowSize() %d x %d scale %d (unscaled "
+          "%d x %d)",
+          aEGLWindowSize.width, aEGLWindowSize.height, scale,
+          aEGLWindowSize.width / scale, aEGLWindowSize.height / scale);
     }
-    mDestroyMutex.Unlock();
   }
-  return paint;
+#  endif
+  return moz_container_wayland_egl_window_set_size(
+      mContainer, aEGLWindowSize.ToUnknownSize(), scale);
 }
 #endif
 
@@ -10123,45 +10017,138 @@ void nsWindow::ClearRenderingQueue() {
   DestroyLayerManager();
 }
 
-void nsWindow::DisableRendering() {
-  LOG("nsWindow::DisableRendering()");
+// nsWindow::OnMap() / nsWindow::OnUnmap() is called from map/unmap mContainer
+// handlers directly as we paint to mContainer.
+void nsWindow::OnMap() {
+  LOG("nsWindow::OnMap");
 
-  if (mGdkWindow) {
-    g_object_set_data(G_OBJECT(mGdkWindow), "nsWindow", nullptr);
-    mGdkWindow = nullptr;
+  {
+    MutexAutoLock lock(mWindowVisibilityMutex);
+    mIsMapped = true;
+
+    EnsureGdkWindow();
+    OnScaleChanged(/* aNotify = */ false);
+
+    if (mIsAlert) {
+      gdk_window_set_override_redirect(mGdkWindow, TRUE);
+    }
+
+#ifdef MOZ_X11
+    if (GdkIsX11Display()) {
+      mSurfaceProvider.Initialize(GetX11Window(), GetShapedState());
+
+      // Set window manager hint to keep fullscreen windows composited.
+      //
+      // If the window were to get unredirected, there could be visible
+      // tearing because Gecko does not align its framebuffer updates with
+      // vblank.
+      SetCompositorHint(GTK_WIDGET_COMPOSITED_ENABLED);
+    }
+#endif
+#ifdef MOZ_WAYLAND
+    if (GdkIsWaylandDisplay()) {
+      mSurfaceProvider.Initialize(this);
+    }
+#endif
+  }
+
+  if (mIsDragPopup) {
+    if (GdkIsWaylandDisplay()) {
+      // Disable painting to the widget on Wayland as we paint directly to the
+      // widget. Wayland compositors does not paint wl_subsurface
+      // of D&D widget.
+      if (GtkWidget* parent = gtk_widget_get_parent(mShell)) {
+        GtkWidgetDisableUpdates(parent);
+      }
+      GtkWidgetDisableUpdates(mShell);
+      GtkWidgetDisableUpdates(GTK_WIDGET(mContainer));
+    } else {
+      // Disable rendering of parent container on X11 to avoid flickering.
+      if (GtkWidget* parent = gtk_widget_get_parent(mShell)) {
+        gtk_widget_set_opacity(parent, 0.0);
+      }
+    }
+  }
+
+  if (mWindowType == WindowType::Popup) {
+    if (mNoAutoHide) {
+      gint wmd = ConvertBorderStyles(mBorderStyle);
+      if (wmd != -1) {
+        gdk_window_set_decorations(mGdkWindow, (GdkWMDecoration)wmd);
+      }
+    }
+    // If the popup ignores mouse events, set an empty input shape.
+    SetInputRegion(mInputRegion);
+  }
+
+  RefreshWindowClass();
+
+  // We're not mapped yet but we have already created compositor.
+  if (mCompositorWidgetDelegate) {
+    ConfigureCompositor();
+  }
+
+  LOG("  finished, new GdkWindow %p XID 0x%lx\n", mGdkWindow, GetX11Window());
+}
+
+void nsWindow::OnUnmap() {
+  LOG("nsWindow::OnUnmap");
+
+  {
+    MutexAutoLock lock(mWindowVisibilityMutex);
+    mIsMapped = false;
+
+    if (mSourceDragContext) {
+      static auto sGtkDragCancel =
+          (void (*)(GdkDragContext*))dlsym(RTLD_DEFAULT, "gtk_drag_cancel");
+      if (sGtkDragCancel) {
+        sGtkDragCancel(mSourceDragContext);
+        mSourceDragContext = nullptr;
+      }
+    }
+
+    if (mGdkWindow) {
+      g_object_set_data(G_OBJECT(mGdkWindow), "nsWindow", nullptr);
+      mGdkWindow = nullptr;
+    }
+
+    // Clear resources (mainly XWindow) stored at GtkCompositorWidget.
+    // It makes sure we don't paint to it when nsWindow becomes hiden/deleted
+    // and XWindow is released.
+    if (mCompositorWidgetDelegate) {
+      mCompositorWidgetDelegate->CleanupResources();
+    }
+
+    // Clear nsWindow resources used for old (in-thread) rendering.
+    mSurfaceProvider.CleanupResources();
   }
 
   // Until Bug 1654938 is fixed we delete layer manager for hidden popups,
   // otherwise it can easily hold 1GB+ memory for long time.
   if (mWindowType == WindowType::Popup) {
     DestroyLayerManager();
-    mSurfaceProvider.CleanupResources();
   } else {
-#ifdef MOZ_WAYLAND
-    // Widget is backed by OpenGL EGLSurface created over wl_surface
-    // owned by mContainer.
-    // RenderCompositorEGL::Resume() deletes recent EGLSurface based on
-    // wl_surface owned by mContainer and creates a new fallback EGLSurface.
-    // Then we can delete wl_surface in moz_container_wayland_unmap().
+    // Widget is backed by OpenGL EGLSurface created over wl_surface/XWindow.
+    //
+    // RenderCompositorEGL::Resume() deletes recent EGLSurface,
+    // calls nsWindow::GetNativeData(NS_NATIVE_EGL_WINDOW) from compositor
+    // thread to get new native rendering surface.
+    //
+    // For hidden/unmapped windows we return nullptr NS_NATIVE_EGL_WINDOW at
+    // nsWindow::GetNativeData() so RenderCompositorEGL::Resume() creates
+    // offscreen fallback EGLSurface to avoid compositor pause.
+    //
     // We don't want to pause compositor as it may lead to whole
     // browser freeze (Bug 1777664).
-    ///
-    // We don't need to do such operation for SW backend as
-    // WindowSurfaceWaylandMB::Commit() gets wl_surface from
-    // MozContainer every commit.
-    if (moz_container_wayland_has_egl_window(mContainer) &&
-        mCompositorWidgetDelegate) {
-      if (CompositorBridgeChild* remoteRenderer = GetRemoteRenderer()) {
-        // Call DisableRendering() to make GtkCompositorWidget hidden.
-        // Then SendResume() will create fallback EGLSurface, see
-        // GLContextEGL::CreateEGLSurfaceForCompositorWidget().
-        mCompositorWidgetDelegate->DisableRendering();
-        remoteRenderer->SendResume();
-        mCompositorWidgetDelegate->EnableRendering(GetX11Window(),
-                                                   GetShapedState());
-      }
+    //
+    // If RenderCompositorSWGL compositor is used (SW fallback)
+    // RenderCompositorSWGL::Resume() only requests full render for next paint
+    // as wl_surface/XWindow is managed by WindowSurfaceProvider owned
+    // directly by GtkCompositorWidget and that's covered by
+    // mCompositorWidgetDelegate->CleanupResources() call above.
+    if (CompositorBridgeChild* remoteRenderer = GetRemoteRenderer()) {
+      remoteRenderer->SendResume();
     }
-#endif
   }
 }
 
diff --git a/widget/gtk/nsWindow.h b/widget/gtk/nsWindow.h
index f8fe344f09..25d68129d8 100644
--- a/widget/gtk/nsWindow.h
+++ b/widget/gtk/nsWindow.h
@@ -175,6 +175,7 @@ class nsWindow final : public nsBaseWidget {
   void MoveToWorkspace(const nsAString& workspaceID) override;
   void Enable(bool aState) override;
   void SetFocus(Raise, mozilla::dom::CallerType aCallerType) override;
+  void ResetScreenBounds();
   LayoutDeviceIntRect GetScreenBounds() override;
   LayoutDeviceIntRect GetClientBounds() override;
   LayoutDeviceIntSize GetClientSize() override;
@@ -411,7 +412,6 @@ class nsWindow final : public nsBaseWidget {
    */
   static GtkWindowDecoration GetSystemGtkWindowDecoration();
 
-  static bool GetTopLevelWindowActiveState(nsIFrame* aFrame);
   static bool TitlebarUseShapeMask();
   bool IsRemoteContent() { return HasRemoteContent(); }
   void NativeMoveResizeWaylandPopupCallback(const GdkRectangle* aFinalSize,
@@ -461,8 +461,6 @@ class nsWindow final : public nsBaseWidget {
   // rendering queue blocking (see Bug 1782948).
   void ClearRenderingQueue();
 
-  void DisableRendering();
-
   bool ApplyEnterLeaveMutterWorkaround();
 
   void NotifyOcclusionState(mozilla::widget::OcclusionState aState) override;
@@ -553,6 +551,9 @@ class nsWindow final : public nsBaseWidget {
   GtkWidget* mShell = nullptr;
   MozContainer* mContainer = nullptr;
   GdkWindow* mGdkWindow = nullptr;
+  mozilla::Maybe<GdkPoint> mGdkWindowOrigin;
+  mozilla::Maybe<GdkPoint> mGdkWindowRootOrigin;
+
   PlatformCompositorWidgetDelegate* mCompositorWidgetDelegate = nullptr;
   mozilla::Atomic<WindowCompositorState, mozilla::Relaxed> mCompositorState{
       COMPOSITOR_ENABLED};
@@ -633,10 +634,14 @@ class nsWindow final : public nsBaseWidget {
   mozilla::Mutex mTitlebarRectMutex;
   LayoutDeviceIntRect mTitlebarRect MOZ_GUARDED_BY(mTitlebarRectMutex);
 
-  mozilla::Mutex mDestroyMutex;
+  // This mutex protect window visibility changes.
+  mozilla::Mutex mWindowVisibilityMutex;
 
+  // This track real window visibility from OS perspective.
+  // It's set by OnMap/OnUnmap which is based on Gtk events.
+  mozilla::Atomic<bool, mozilla::Relaxed> mIsMapped;
   // Has this widget been destroyed yet?
-  bool mIsDestroyed : 1;
+  mozilla::Atomic<bool, mozilla::Relaxed> mIsDestroyed;
   // mIsShown tracks requested visible status from browser perspective, i.e.
   // if the window should be visible or now.
   bool mIsShown : 1;
@@ -646,9 +651,6 @@ class nsWindow final : public nsBaseWidget {
   // that the window is not actually visible but we report to browser that
   // it is visible (mIsShown == true).
   bool mNeedsShow : 1;
-  // This track real window visibility from OS perspective.
-  // It's set by OnMap/OnUnmap which is based on Gtk events.
-  bool mIsMapped : 1;
   // is this widget enabled?
   bool mEnabled : 1;
   // has the native window for this been created yet?
@@ -802,11 +804,6 @@ class nsWindow final : public nsBaseWidget {
 
   void DispatchMissedButtonReleases(GdkEventCrossing* aGdkEvent);
 
-  // When window widget gets mapped/unmapped we need to configure
-  // underlying GdkWindow properly. Otherwise we'll end up with
-  // rendering to released window.
-  void ConfigureGdkWindow();
-  void ReleaseGdkWindow();
   void ConfigureCompositor();
 
   bool IsAlwaysUndecoratedWindow() const;
@@ -996,9 +993,9 @@ class nsWindow final : public nsBaseWidget {
   void RequestRepaint(LayoutDeviceIntRegion& aRepaintRegion);
 
 #ifdef MOZ_X11
-  typedef enum {GTK_WIDGET_COMPOSIDED_DEFAULT = 0,
-                GTK_WIDGET_COMPOSIDED_DISABLED = 1,
-                GTK_WIDGET_COMPOSIDED_ENABLED = 2} WindowComposeRequest;
+  typedef enum {GTK_WIDGET_COMPOSITED_DEFAULT = 0,
+                GTK_WIDGET_COMPOSITED_DISABLED = 1,
+                GTK_WIDGET_COMPOSITED_ENABLED = 2} WindowComposeRequest;
   void SetCompositorHint(WindowComposeRequest aState);
   bool ConfigureX11GLVisual();
 #endif
diff --git a/widget/headless/HeadlessLookAndFeelGTK.cpp b/widget/headless/HeadlessLookAndFeelGTK.cpp
index 462a877f34..aa55bcc347 100644
--- a/widget/headless/HeadlessLookAndFeelGTK.cpp
+++ b/widget/headless/HeadlessLookAndFeelGTK.cpp
@@ -32,9 +32,6 @@ nsresult HeadlessLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
     case IntID::CaretWidth:
       aResult = 1;
       break;
-    case IntID::ShowCaretDuringSelection:
-      aResult = 0;
-      break;
     case IntID::SelectTextfieldsOnKeyFocus:
       aResult = 1;
       break;
diff --git a/widget/headless/HeadlessScreenHelper.cpp b/widget/headless/HeadlessScreenHelper.cpp
index 4d8dbfa0d1..5a9643c572 100644
--- a/widget/headless/HeadlessScreenHelper.cpp
+++ b/widget/headless/HeadlessScreenHelper.cpp
@@ -32,9 +32,10 @@ LayoutDeviceIntRect HeadlessScreenHelper::GetScreenRect() {
 HeadlessScreenHelper::HeadlessScreenHelper() {
   AutoTArray<RefPtr<Screen>, 1> screenList;
   LayoutDeviceIntRect rect = GetScreenRect();
-  auto ret = MakeRefPtr<Screen>(
-      rect, rect, 24, 24, 0, DesktopToLayoutDeviceScale(),
-      CSSToLayoutDeviceScale(), 96.0f, Screen::IsPseudoDisplay::No);
+  auto ret =
+      MakeRefPtr<Screen>(rect, rect, 24, 24, 0, DesktopToLayoutDeviceScale(),
+                         CSSToLayoutDeviceScale(), 96.0f,
+                         Screen::IsPseudoDisplay::No, Screen::IsHDR::No);
   screenList.AppendElement(ret.forget());
   ScreenManager::Refresh(std::move(screenList));
 }
diff --git a/widget/headless/HeadlessWidget.cpp b/widget/headless/HeadlessWidget.cpp
index 083d026d3c..419b3bf940 100644
--- a/widget/headless/HeadlessWidget.cpp
+++ b/widget/headless/HeadlessWidget.cpp
@@ -160,10 +160,9 @@ void HeadlessWidget::GetCompositorWidgetInitData(
 nsIWidget* HeadlessWidget::GetTopLevelWidget() { return mTopLevel; }
 
 void HeadlessWidget::RaiseWindow() {
-  MOZ_ASSERT(mWindowType == WindowType::TopLevel ||
-                 mWindowType == WindowType::Dialog ||
-                 mWindowType == WindowType::Sheet,
-             "Raising a non-toplevel window.");
+  MOZ_ASSERT(
+      mWindowType == WindowType::TopLevel || mWindowType == WindowType::Dialog,
+      "Raising a non-toplevel window.");
 
   // Do nothing if this is the currently active window.
   RefPtr<HeadlessWidget> activeWindow = GetActiveWindow();
@@ -204,7 +203,7 @@ void HeadlessWidget::Show(bool aState) {
   //     so we don't focus them by default.
   if (aState && !mAlwaysOnTop &&
       (mWindowType == WindowType::TopLevel ||
-       mWindowType == WindowType::Dialog || mWindowType == WindowType::Sheet)) {
+       mWindowType == WindowType::Dialog)) {
     RaiseWindow();
   }
 
diff --git a/widget/nsBaseClipboard.cpp b/widget/nsBaseClipboard.cpp
index 333d154e70..9ffc53b4c2 100644
--- a/widget/nsBaseClipboard.cpp
+++ b/widget/nsBaseClipboard.cpp
@@ -340,7 +340,7 @@ class SafeContentAnalysisResultCallback final
   NS_IMETHODIMP Error(nsresult aError) override {
     using namespace mozilla::contentanalysis;
     Callback(ContentAnalysisResult::FromNoResult(
-        NoContentAnalysisResult::ERROR_OTHER));
+        NoContentAnalysisResult::DENY_DUE_TO_OTHER_ERROR));
     return NS_OK;
   }
 
@@ -379,13 +379,18 @@ CheckClipboardContentAnalysisAsText(
   }
   nsString text;
   if (NS_FAILED(textData->GetData(text))) {
-    return mozilla::Err(NoContentAnalysisResult::ERROR_OTHER);
+    return mozilla::Err(NoContentAnalysisResult::DENY_DUE_TO_OTHER_ERROR);
+  }
+  if (text.IsEmpty()) {
+    // Content Analysis doesn't expect to analyze an empty string.
+    // Just approve it.
+    return true;
   }
   RefPtr<mozilla::dom::WindowGlobalParent> window =
       mozilla::dom::WindowGlobalParent::GetByInnerWindowId(aInnerWindowId);
   if (!window) {
     // The window has gone away in the meantime
-    return mozilla::Err(NoContentAnalysisResult::ERROR_OTHER);
+    return mozilla::Err(NoContentAnalysisResult::DENY_DUE_TO_OTHER_ERROR);
   }
   nsCOMPtr<nsIContentAnalysisRequest> contentAnalysisRequest =
       new ContentAnalysisRequest(
@@ -395,7 +400,7 @@ CheckClipboardContentAnalysisAsText(
   nsresult rv = aContentAnalysis->AnalyzeContentRequestCallback(
       contentAnalysisRequest, /* aAutoAcknowledge */ true, aResolver);
   if (NS_FAILED(rv)) {
-    return mozilla::Err(NoContentAnalysisResult::ERROR_OTHER);
+    return mozilla::Err(NoContentAnalysisResult::DENY_DUE_TO_OTHER_ERROR);
   }
   return true;
 }
@@ -420,7 +425,7 @@ CheckClipboardContentAnalysisAsFile(
       rv = file->GetPath(filePath);
     } else {
       MOZ_ASSERT_UNREACHABLE("clipboard data had kFileMime but no nsIFile!");
-      return mozilla::Err(NoContentAnalysisResult::ERROR_OTHER);
+      return mozilla::Err(NoContentAnalysisResult::DENY_DUE_TO_OTHER_ERROR);
     }
   }
   if (NS_FAILED(rv) || filePath.IsEmpty()) {
@@ -430,7 +435,7 @@ CheckClipboardContentAnalysisAsFile(
       mozilla::dom::WindowGlobalParent::GetByInnerWindowId(aInnerWindowId);
   if (!window) {
     // The window has gone away in the meantime
-    return mozilla::Err(NoContentAnalysisResult::ERROR_OTHER);
+    return mozilla::Err(NoContentAnalysisResult::DENY_DUE_TO_OTHER_ERROR);
   }
   // Let the content analysis code calculate the digest
   nsCOMPtr<nsIContentAnalysisRequest> contentAnalysisRequest =
@@ -443,7 +448,7 @@ CheckClipboardContentAnalysisAsFile(
       contentAnalysisRequest,
       /* aAutoAcknowledge */ true, aResolver);
   if (NS_FAILED(rv)) {
-    return mozilla::Err(NoContentAnalysisResult::ERROR_OTHER);
+    return mozilla::Err(NoContentAnalysisResult::DENY_DUE_TO_OTHER_ERROR);
   }
   return true;
 }
@@ -463,14 +468,15 @@ static void CheckClipboardContentAnalysis(
   if (!aWindow || aWindow->GetBrowsingContext()->IsChrome() ||
       aWindow->IsInProcess()) {
     aResolver->Callback(ContentAnalysisResult::FromNoResult(
-        NoContentAnalysisResult::CONTEXT_EXEMPT_FROM_CONTENT_ANALYSIS));
+        NoContentAnalysisResult::
+            ALLOW_DUE_TO_CONTEXT_EXEMPT_FROM_CONTENT_ANALYSIS));
     return;
   }
   nsCOMPtr<nsIContentAnalysis> contentAnalysis =
       mozilla::components::nsIContentAnalysis::Service();
   if (!contentAnalysis) {
     aResolver->Callback(ContentAnalysisResult::FromNoResult(
-        NoContentAnalysisResult::ERROR_OTHER));
+        NoContentAnalysisResult::DENY_DUE_TO_OTHER_ERROR));
     return;
   }
 
@@ -478,7 +484,7 @@ static void CheckClipboardContentAnalysis(
   nsresult rv = contentAnalysis->GetIsActive(&contentAnalysisIsActive);
   if (MOZ_LIKELY(NS_FAILED(rv) || !contentAnalysisIsActive)) {
     aResolver->Callback(ContentAnalysisResult::FromNoResult(
-        NoContentAnalysisResult::CONTENT_ANALYSIS_NOT_ACTIVE));
+        NoContentAnalysisResult::ALLOW_DUE_TO_CONTENT_ANALYSIS_NOT_ACTIVE));
     return;
   }
 
@@ -488,7 +494,7 @@ static void CheckClipboardContentAnalysis(
   rv = aTransferable->FlavorsTransferableCanExport(flavors);
   if (NS_WARN_IF(NS_FAILED(rv))) {
     aResolver->Callback(ContentAnalysisResult::FromNoResult(
-        NoContentAnalysisResult::ERROR_OTHER));
+        NoContentAnalysisResult::DENY_DUE_TO_OTHER_ERROR));
     return;
   }
   bool keepChecking = true;
@@ -515,7 +521,7 @@ static void CheckClipboardContentAnalysis(
     if (!textResult.unwrap()) {
       // Couldn't get file or text data from this
       aResolver->Callback(ContentAnalysisResult::FromNoResult(
-          NoContentAnalysisResult::ERROR_COULD_NOT_GET_DATA));
+          NoContentAnalysisResult::ALLOW_DUE_TO_COULD_NOT_GET_DATA));
       return;
     }
   }
diff --git a/widget/nsIDragSession.idl b/widget/nsIDragSession.idl
index e96e6fc1c7..8dbf93e719 100644
--- a/widget/nsIDragSession.idl
+++ b/widget/nsIDragSession.idl
@@ -135,7 +135,7 @@ interface nsIDragSession : nsISupports
   /**
    * Returns true if current session was started with synthesized drag start.
    */
-  [notxpcom, nostdcall] bool isSynthesizedForTests();
+  [notxpcom, nostdcall] boolean isSynthesizedForTests();
 
   /**
    * Sets drag end point of synthesized session when the test does not dispatch
@@ -147,5 +147,5 @@ interface nsIDragSession : nsISupports
    * Returns true if the session is for dragging text in a text in text control
    * element.
    */
-  [notxpcom, nostdcall] bool isDraggingTextInTextControl();
+  [notxpcom, nostdcall] boolean isDraggingTextInTextControl();
 };
diff --git a/widget/nsIMacDockSupport.idl b/widget/nsIMacDockSupport.idl
index 04d6dca774..6f0f1adbae 100644
--- a/widget/nsIMacDockSupport.idl
+++ b/widget/nsIMacDockSupport.idl
@@ -41,7 +41,7 @@ interface nsIMacDockSupport : nsISupports
    * True if this app is in the list of apps that are persisted to the macOS
    * Dock (as if the user selected "Keep in Dock").
    */
-  readonly attribute bool isAppInDock;
+  readonly attribute boolean isAppInDock;
 
   /**
    * Ensure that there is a tile for this app in the list of apps that are
@@ -66,6 +66,6 @@ interface nsIMacDockSupport : nsISupports
    * @return true if the app was already in the list of persisted apps or if it
    *   was successfully added, else returns false.
    */
-  bool ensureAppIsPinnedToDock([optional] in AString aAppPath,
-                               [optional] in AString aAppToReplacePath);
+  boolean ensureAppIsPinnedToDock([optional] in AString aAppPath,
+                                  [optional] in AString aAppToReplacePath);
 };
diff --git a/widget/nsIPrintSettings.idl b/widget/nsIPrintSettings.idl
index efed9efce6..daf0e145f4 100644
--- a/widget/nsIPrintSettings.idl
+++ b/widget/nsIPrintSettings.idl
@@ -203,7 +203,7 @@ interface nsIPrintSettings : nsISupports
    * to make best use of the space on the sheet. Specifically, this returns
    * true IFF `numPagesPerSheet` is set to 2 or 6 pages-per-sheet.
    */
-  [noscript, notxpcom, nostdcall] bool HasOrthogonalPagesPerSheet();
+  [noscript, notxpcom, nostdcall] boolean HasOrthogonalPagesPerSheet();
 
   /**
    * Makes a new copy
@@ -220,7 +220,7 @@ interface nsIPrintSettings : nsISupports
    * therefore print. The printer name is ignored and it allows for a small
    * delta in sizes to allow for rounding differences.
    */
-  bool equivalentTo(in nsIPrintSettings aPrintSettings);
+  boolean equivalentTo(in nsIPrintSettings aPrintSettings);
 
   /**
    * The edge measurements define the positioning of the headers
@@ -335,7 +335,7 @@ interface nsIPrintSettings : nsISupports
    */
   attribute AString toFileName;
 
-  attribute nsIOutputStream outputStream; /* for kOutputDestinationPrinter */
+  attribute nsIOutputStream outputStream; /* for kOutputDestinationStream */
 
   [infallible] attribute long printPageDelay; /* in milliseconds */
 
diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
index 81e952a8c6..06eab558eb 100644
--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -668,12 +668,6 @@ class nsIWidget : public nsISupports {
   virtual void SetModal(bool aModal) = 0;
 
   /**
-   * Make the non-modal window opened by modal window fake-modal, that will
-   * call SetFakeModal(false) on destroy on Cocoa.
-   */
-  virtual void SetFakeModal(bool aModal) { SetModal(aModal); }
-
-  /**
    * Are we app modal. Currently only implemented on Cocoa.
    */
   virtual bool IsRunningAppModal() { return false; }
@@ -784,10 +778,6 @@ class nsIWidget : public nsISupports {
   virtual void Resize(double aX, double aY, double aWidth, double aHeight,
                       bool aRepaint) = 0;
 
-  virtual mozilla::Maybe<bool> IsResizingNativeWidget() {
-    return mozilla::Nothing();
-  }
-
   /**
    * Resize the widget so that the inner client area has the given size.
    *
diff --git a/widget/nsXPLookAndFeel.cpp b/widget/nsXPLookAndFeel.cpp
index 9eabbd84b6..0c5b5207f2 100644
--- a/widget/nsXPLookAndFeel.cpp
+++ b/widget/nsXPLookAndFeel.cpp
@@ -128,7 +128,6 @@ static const char sIntPrefs[][45] = {
     "ui.caretBlinkTime",
     "ui.caretBlinkCount",
     "ui.caretWidth",
-    "ui.caretVisibleWithSelection",
     "ui.selectTextfieldsOnKeyFocus",
     "ui.submenuDelay",
     "ui.menusCanOverlapOSBar",
@@ -152,6 +151,7 @@ static const char sIntPrefs[][45] = {
     "ui.windowsAccentColorInTitlebar",
     "ui.macBigSurTheme",
     "ui.macRTL",
+    "ui.macTitlebarHeight",
     "ui.alertNotificationOrigin",
     "ui.scrollToClick",
     "ui.IMERawInputUnderlineStyle",
@@ -167,6 +167,7 @@ static const char sIntPrefs[][45] = {
     "ui.scrollbarFadeDuration",
     "ui.contextMenuOffsetVertical",
     "ui.contextMenuOffsetHorizontal",
+    "ui.tooltipOffsetVertical",
     "ui.GtkCSDAvailable",
     "ui.GtkCSDMinimizeButton",
     "ui.GtkCSDMaximizeButton",
@@ -186,7 +187,6 @@ static const char sIntPrefs[][45] = {
     "ui.titlebarRadius",
     "ui.titlebarButtonSpacing",
     "ui.dynamicRange",
-    "ui.videoDynamicRange",
     "ui.panelAnimations",
     "ui.hideCursorWhileTyping",
     "ui.gtkThemeFamily",
@@ -711,6 +711,7 @@ nscolor nsXPLookAndFeel::GetStandinForNativeColor(ColorID aID,
       // Seems to be the default color (hardcoded because of bug 1065998)
       COLOR(MozNativehyperlinktext, 0x00, 0x66, 0xCC)
       COLOR(MozNativevisitedhyperlinktext, 0x55, 0x1A, 0x8B)
+      COLOR(MozAutofillBackground, 0xff, 0xfc, 0xc8)
     default:
       break;
   }
@@ -855,6 +856,11 @@ Maybe<nscolor> nsXPLookAndFeel::GenericDarkColor(ColorID aID) {
     case ColorID::Inactivecaption:
       color = NS_RGB(28, 27, 34);
       break;
+    case ColorID::MozAutofillBackground:
+      // This is the light version of this color, but darkened to have good
+      // contrast with our white-ish FieldText.
+      color = NS_RGB(0x72, 0x6c, 0x00);
+      break;
     default:
       return Nothing();
   }
diff --git a/widget/tests/mochitest.toml b/widget/tests/mochitest.toml
index 4a4a9d2729..93e3adf733 100644
--- a/widget/tests/mochitest.toml
+++ b/widget/tests/mochitest.toml
@@ -36,7 +36,10 @@ skip-if = ["display == 'wayland'"] # Bug 1879835
 support-files = "file_test_clipboard_getDataSnapshotSync.js"
 
 ["test_contextmenu_by_mouse_on_unix.html"]
-run-if = ["os == 'linux'"]
+run-if = [
+  "os == 'linux'",
+  "os == 'android'",
+]
 skip-if = ["headless"] # headless widget doesn't dispatch contextmenu event by mouse event.
 
 ["test_keypress_event_with_alt_on_mac.html"]
diff --git a/widget/tests/test_assign_event_data.html b/widget/tests/test_assign_event_data.html
index 1da9bb535f..26d214edce 100644
--- a/widget/tests/test_assign_event_data.html
+++ b/widget/tests/test_assign_event_data.html
@@ -59,6 +59,7 @@
 <body>
 <div id="display">
   <input id="input-text">
+  <div contenteditable id="contenteditable"><br></div>
   <button id="button">button</button>
   <a id="a" href="about:blank">hyper link</a>
   <span id="pointer-target">span</span>
@@ -352,6 +353,44 @@ const kTests = [
     },
     todoMismatch: [ ],
   },
+  { description: "InternalLegacyTextEvent (input at key input)",
+    targetID: "input-text", eventType: "textInput",
+    dispatchEvent() {
+      const input = document.getElementById(this.targetID);
+      input.value = "";
+      input.focus();
+      synthesizeNativeKey(KEYBOARD_LAYOUT_EN_US, kIsWin ? WIN_VK_B : MAC_VK_ANSI_B,
+                          { shiftKey: true }, "B", "B");
+      observeKeyUpOnContent(KeyboardEvent.DOM_VK_B, runNextTest);
+      return true;
+    },
+    canRun() {
+      return (kIsMac || kIsWin);
+    },
+    todoMismatch: [],
+  },
+  { description: "InternalLegacyTextEvent (paste)",
+    targetID: "contenteditable", eventType: "textInput",
+    async dispatchEvent() {
+      const editingHost = document.getElementById(this.targetID);
+      editingHost.innerHTML = "abc";
+      editingHost.focus();
+      getSelection().selectAllChildren(editingHost);
+      synthesizeNativeKey(KEYBOARD_LAYOUT_EN_US, kIsWin ? WIN_VK_C : MAC_VK_ANSI_C,
+                          { accelKey: true }, "", "c");
+      const waitForInput = new Promise(resolve => {
+        editingHost.addEventListener("input", resolve, {once: true});
+      });
+      // In this case, TextEvent.data is stored with a dataTransfer.
+      synthesizeNativeKey(KEYBOARD_LAYOUT_EN_US, kIsWin ? WIN_VK_V : MAC_VK_ANSI_V,
+                          { accelKey: true }, "", "v");
+      await waitForInput;
+    },
+    canRun() {
+      return (kIsMac || kIsWin);
+    },
+    todoMismatch: [],
+  },
   { description: "WidgetMouseScrollEvent (DOMMouseScroll, vertical)",
     targetID: "input-text", eventType: "DOMMouseScroll",
     dispatchEvent() {
@@ -615,7 +654,7 @@ const kTests = [
   },
 ];
 
-function doTest(aTest) {
+async function doTest(aTest) {
   if (!aTest.canRun()) {
     SimpleTest.executeSoon(runNextTest);
     return;
@@ -650,7 +689,7 @@ function doTest(aTest) {
       runNextTest();
     }
   };
-  var testWillCallRunNextTest = aTest.dispatchEvent();
+  var testWillCallRunNextTest = await aTest.dispatchEvent();
 }
 
 var gIndex = -1;
@@ -695,7 +734,8 @@ function init() {
                                     ["mousewheel.with_alt.action", 0],
                                     ["mousewheel.with_alt.action.override_x", -1],
                                     ["mousewheel.with_meta.action", 0],
-                                    ["mousewheel.with_meta.action.override_x", -1]]}, runNextTest);
+                                    ["mousewheel.with_meta.action.override_x", -1],
+                                    ["dom.events.textevent.enabled", true]]}, runNextTest);
 }
 
 function finish() {
diff --git a/widget/tests/window_composition_text_querycontent.xhtml b/widget/tests/window_composition_text_querycontent.xhtml
index 4806d0d187..ea224a1636 100644
--- a/widget/tests/window_composition_text_querycontent.xhtml
+++ b/widget/tests/window_composition_text_querycontent.xhtml
@@ -806,6 +806,16 @@ function checkInputEvent(aEvent, aIsComposing, aInputType, aData, aTargetRanges,
   }
 }
 
+function checkTextInputEvent(aEvent, aData, aDescription) {
+  if (aEvent.type !== "textInput") {
+    throw new Error(`${aDescription}: "${aEvent.type}" is not TextEvent`);
+  }
+  ok(TextEvent.isInstance(aEvent), `"${aEvent.type}" event should be dispatched with TextEvent interface: ${aDescription}`);
+  is(aEvent.cancelable, true, `"${aEvent.type}" event should be cancelable: ${aDescription}`);
+  is(aEvent.bubbles, true, `"${aEvent.type}" event should always bubble: ${aDescription}`);
+  is(aEvent.data, aData, `data of "${aEvent.type}" event should be ${aData}: ${aDescription}`);
+}
+
 function runCompositionCommitAsIsTest()
 {
   textarea.focus();
@@ -824,6 +834,7 @@ function runCompositionCommitAsIsTest()
   textarea.addEventListener("compositionupdate", handler, true);
   textarea.addEventListener("compositionend", handler, true);
   textarea.addEventListener("beforeinput", handler, true);
+  textarea.addEventListener("textInput", handler, true);
   textarea.addEventListener("input", handler, true);
   textarea.addEventListener("text", handler, true);
 
@@ -842,22 +853,29 @@ function runCompositionCommitAsIsTest()
     });
   is(textarea.value, "\u3042", "runCompositionCommitAsIsTest: textarea doesn't have composition string #1");
 
+  is(result.findIndex(value => value.type == "textInput"), -1,
+    "runCompositionCommitAsIsTest: no textInput event should be fired before commit #1");
+
   clearResult();
   synthesizeComposition({ type: "compositioncommitasis", key: { key: "Enter" } });
 
-  is(result.length, 4,
-     "runCompositionCommitAsIsTest: 4 events should be fired after dispatching compositioncommitasis #1");
+  is(result.length, 5,
+     "runCompositionCommitAsIsTest: 5 events should be fired after dispatching compositioncommitasis #1");
   is(result[0].type, "text",
      "runCompositionCommitAsIsTest: text should be fired after dispatching compositioncommitasis because it's dispatched when there is composing string #1");
   is(result[1].type, "beforeinput",
      "runCompositionCommitAsIsTest: beforeinput should be fired after dispatching compositioncommitasis because it's dispatched when there is composing string #1");
   checkInputEvent(result[1], true, "insertCompositionText", "\u3042", [],
                   "runCompositionCommitAsIsTest: after dispatching compositioncommitasis #1");
-  is(result[2].type, "compositionend",
+  is(result[2].type, "textInput",
+     "runCompositionCommitAsIsText: textInput should be fired after dispatching compositioncommitasis because it's after the last beforeinput for the composition #1");
+  checkTextInputEvent(result[2], "\u3042",
+                      "runCompositionCommitAsIsText: after dispatching compositioncommitasis #1");
+  is(result[3].type, "compositionend",
      "runCompositionCommitAsIsTest: compositionend should be fired after dispatching compositioncommitasis #1");
-  is(result[3].type, "input",
+  is(result[4].type, "input",
      "runCompositionCommitAsIsTest: input should be fired after dispatching compositioncommitasis #1");
-  checkInputEvent(result[3], false, "insertCompositionText", "\u3042", [],
+  checkInputEvent(result[4], false, "insertCompositionText", "\u3042", [],
                   "runCompositionCommitAsIsTest: after dispatching compositioncommitasis #1");
   is(textarea.value, "\u3042", "runCompositionCommitAsIsTest: textarea doesn't have committed string #1");
 
@@ -887,6 +905,8 @@ function runCompositionCommitAsIsTest()
       "key": { key: "KEY_Enter", type: "keydown" },
     });
   is(textarea.value, "\u3042", "runCompositionCommitAsIsTest: textarea doesn't have committed string #2");
+  isnot(result.findIndex(value => value.type == "textInput"), -1,
+        "runCompositionCommitAsIsTest: a textInput event should be fired before commit #2");
 
   clearResult();
   synthesizeComposition({ type: "compositioncommitasis", key: { key: "KEY_Enter", type: "keyup" } });
@@ -928,6 +948,8 @@ function runCompositionCommitAsIsTest()
       "key": { key: "KEY_Escape", type: "keydown" },
     });
   is(textarea.value, "", "runCompositionCommitAsIsTest: textarea has non-empty composition string #3");
+  todo_isnot(result.findIndex(value => value.type == "textInput"), -1,
+             "runCompositionCommitAsIsTest: a textInput event should be fired immediately before commit #3");
 
   clearResult();
   synthesizeComposition({ type: "compositioncommitasis", key: { key: "KEY_Escape", type: "keyup" } });
@@ -946,6 +968,7 @@ function runCompositionCommitAsIsTest()
   textarea.removeEventListener("compositionupdate", handler, true);
   textarea.removeEventListener("compositionend", handler, true);
   textarea.removeEventListener("beforeinput", handler, true);
+  textarea.removeEventListener("textInput", handler, true);
   textarea.removeEventListener("input", handler, true);
   textarea.removeEventListener("text", handler, true);
 }
@@ -968,6 +991,7 @@ function runCompositionCommitTest()
   textarea.addEventListener("compositionupdate", handler, true);
   textarea.addEventListener("compositionend", handler, true);
   textarea.addEventListener("beforeinput", handler, true);
+  textarea.addEventListener("textInput", handler, true);
   textarea.addEventListener("input", handler, true);
   textarea.addEventListener("text", handler, true);
 
@@ -985,12 +1009,14 @@ function runCompositionCommitTest()
       "key": { key: "a", type: "keydown" },
     });
   is(textarea.value, "\u3042", "runCompositionCommitTest: textarea doesn't have composition string #1");
+  is(result.findIndex(value => value.type == "textInput"), -1,
+    "runCompositionCommitTest: no textInput event should be fired before commit #1");
 
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "\u3043", key: { key: "a", type: "keyup" } });
 
-  is(result.length, 5,
-     "runCompositionCommitTest: 5 events should be fired after dispatching compositioncommit #1");
+  is(result.length, 6,
+     "runCompositionCommitTest: 6 events should be fired after dispatching compositioncommit #1");
   is(result[0].type, "compositionupdate",
      "runCompositionCommitTest: compositionupdate should be fired after dispatching compositioncommit because it's dispatched when there is composing string #1");
   is(result[1].type, "text",
@@ -999,16 +1025,21 @@ function runCompositionCommitTest()
      "runCompositionCommitTest: beforeinput should be fired after dispatching compositioncommit because it's dispatched when there is composing string #1");
   checkInputEvent(result[2], true, "insertCompositionText", "\u3043", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #1");
-  is(result[3].type, "compositionend",
+  is(result[3].type, "textInput",
+     "runCompositionCommitTest: textInput should be fired after dispatching compositioncommit because the preceding beforeinput is last one for the composition #1");
+  checkTextInputEvent(result[3], "\u3043",
+                      "runCompositionCommitTest: after dispatching compositioncommit #1");
+  is(result[4].type, "compositionend",
      "runCompositionCommitTest: compositionend should be fired after dispatching compositioncommit #1");
-  is(result[4].type, "input",
+  is(result[5].type, "input",
      "runCompositionCommitTest: input should be fired after dispatching compositioncommit #1");
-  checkInputEvent(result[4], false, "insertCompositionText", "\u3043", [],
+  checkInputEvent(result[5], false, "insertCompositionText", "\u3043", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #1");
   is(textarea.value, "\u3043", "runCompositionCommitTest: textarea doesn't have committed string #1");
 
   // compositioncommit with different committed string when there is already committed string
   textarea.value = "";
+  clearResult();
   synthesizeCompositionChange(
     { "composition":
       { "string": "\u3042",
@@ -1033,12 +1064,14 @@ function runCompositionCommitTest()
       "key": { key: "KEY_Enter", type: "keydown" },
     });
   is(textarea.value, "\u3042", "runCompositionCommitTest: textarea doesn't have committed string #2");
+  is(result.findIndex(value => value.type == "textInput"), -1,
+     "runCompositionCommitTest: no textInput event should be fired before commit #2");
 
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "\u3043", key: { key: "KEY_Enter", type: "keyup" } });
 
-  is(result.length, 5,
-     "runCompositionCommitTest: 5 events should be fired after dispatching compositioncommit #2");
+  is(result.length, 6,
+     "runCompositionCommitTest: 6 events should be fired after dispatching compositioncommit #2");
   is(result[0].type, "compositionupdate",
      "runCompositionCommitTest: compositionupdate should be fired after dispatching compositioncommit #2");
   is(result[1].type, "text",
@@ -1047,16 +1080,21 @@ function runCompositionCommitTest()
      "runCompositionCommitTest: beforeinput should be fired after dispatching compositioncommit #2");
   checkInputEvent(result[2], true, "insertCompositionText", "\u3043", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #2");
-  is(result[3].type, "compositionend",
+  is(result[3].type, "textInput",
+     "runCompositionCommitTest: textInput should be fired after dispatching compositioncommit #2");
+  checkTextInputEvent(result[3], "\u3043",
+                  "runCompositionCommitTest: after dispatching compositioncommit #2");
+  is(result[4].type, "compositionend",
      "runCompositionCommitTest: compositionend should be fired after dispatching compositioncommit #2");
-  is(result[4].type, "input",
+  is(result[5].type, "input",
      "runCompositionCommitTest: input should be fired after dispatching compositioncommit #2");
-  checkInputEvent(result[4], false, "insertCompositionText", "\u3043", [],
+  checkInputEvent(result[5], false, "insertCompositionText", "\u3043", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #2");
   is(textarea.value, "\u3043", "runCompositionCommitTest: textarea doesn't have committed string #2");
 
   // compositioncommit with empty composition string.
   textarea.value = "";
+  clearResult();
   synthesizeCompositionChange(
     { "composition":
       { "string": "\u3042",
@@ -1081,12 +1119,14 @@ function runCompositionCommitTest()
       "key": { key: "KEY_Enter", type: "keydown" },
     });
   is(textarea.value, "", "runCompositionCommitTest: textarea has non-empty composition string #3");
+  is(result.findIndex(value => value.type == "textInput"), -1,
+     "runCompositionCommitTest: no textInput event should be fired before commit #3");
 
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "\u3043", key: { key: "KEY_Enter", type: "keyup" } });
 
-  is(result.length, 5,
-     "runCompositionCommitTest: 5 events should be fired after dispatching compositioncommit #3");
+  is(result.length, 6,
+     "runCompositionCommitTest: 6 events should be fired after dispatching compositioncommit #3");
   is(result[0].type, "compositionupdate",
      "runCompositionCommitTest: compositionupdate should be fired after dispatching compositioncommit #3");
   is(result[1].type, "text",
@@ -1095,11 +1135,15 @@ function runCompositionCommitTest()
      "runCompositionCommitTest: beforeinput should be fired after dispatching compositioncommit #3");
   checkInputEvent(result[2], true, "insertCompositionText", "\u3043", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #3");
-  is(result[3].type, "compositionend",
+  is(result[3].type, "textInput",
+     "runCompositionCommitTest: textInput should be fired after dispatching compositioncommit #3");
+  checkTextInputEvent(result[3], "\u3043",
+                      "runCompositionCommitTest: after dispatching compositioncommit #3");
+  is(result[4].type, "compositionend",
      "runCompositionCommitTest: compositionend should be fired after dispatching compositioncommit #3");
-  is(result[4].type, "input",
+  is(result[5].type, "input",
      "runCompositionCommitTest: input should be fired after dispatching compositioncommit #3");
-  checkInputEvent(result[4], false, "insertCompositionText", "\u3043", [],
+  checkInputEvent(result[5], false, "insertCompositionText", "\u3043", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #3");
   is(textarea.value, "\u3043", "runCompositionCommitTest: textarea doesn't have committed string #3");
 
@@ -1111,19 +1155,23 @@ function runCompositionCommitTest()
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "" });
 
-  is(result.length, 4,
-     "runCompositionCommitTest: 4 events should be fired when inserting empty string with composition");
+  is(result.length, 5,
+     "runCompositionCommitTest: 5 events should be fired when inserting empty string with composition");
   is(result[0].type, "text",
      "runCompositionCommitTest: text should be fired when inserting empty string with composition");
   is(result[1].type, "beforeinput",
      "runCompositionCommitTest: beforeinput should be fired when inserting empty string with composition");
   checkInputEvent(result[1], true, "insertCompositionText", "", [],
                   "runCompositionCommitTest: when inserting empty string with composition");
-  is(result[2].type, "compositionend",
+  is(result[2].type, "textInput",
+     "runCompositionCommitTest: textInput should be fired when inserting empty string with composition");
+  checkTextInputEvent(result[2], "",
+                      "runCompositionCommitTest: when inserting empty string with composition");
+  is(result[3].type, "compositionend",
      "runCompositionCommitTest: compositionend should be fired when inserting empty string with composition");
-  is(result[3].type, "input",
+  is(result[4].type, "input",
      "runCompositionCommitTest: input should be fired when inserting empty string with composition");
-  checkInputEvent(result[3], false, "insertCompositionText", "", [],
+  checkInputEvent(result[4], false, "insertCompositionText", "", [],
                   "runCompositionCommitTest: when inserting empty string with composition");
   is(textarea.value, "abc",
      "runCompositionCommitTest: textarea should keep original value when inserting empty string with composition");
@@ -1136,19 +1184,23 @@ function runCompositionCommitTest()
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "" });
 
-  is(result.length, 4,
-     "runCompositionCommitTest: 4 events should be fired when replacing with empty string with composition");
+  is(result.length, 5,
+     "runCompositionCommitTest: 5 events should be fired when replacing with empty string with composition");
   is(result[0].type, "text",
      "runCompositionCommitTest: text should be fired when replacing with empty string with composition");
   is(result[1].type, "beforeinput",
      "runCompositionCommitTest: beforeinput should be fired when replacing with empty string with composition");
   checkInputEvent(result[1], true, "insertCompositionText", "", [],
                   "runCompositionCommitTest: when replacing with empty string with composition");
-  is(result[2].type, "compositionend",
+  is(result[2].type, "textInput",
+     "runCompositionCommitTest: textInput should be fired when replacing with empty string with composition");
+  checkTextInputEvent(result[2], "",
+                      "runCompositionCommitTest: when replacing with empty string with composition");
+  is(result[3].type, "compositionend",
      "runCompositionCommitTest: compositionend should be fired when replacing with empty string with composition");
-  is(result[3].type, "input",
+  is(result[4].type, "input",
      "runCompositionCommitTest: input should be fired when replacing with empty string with composition");
-  checkInputEvent(result[3], false, "insertCompositionText", "", [],
+  checkInputEvent(result[4], false, "insertCompositionText", "", [],
                   "runCompositionCommitTest: when replacing with empty string with composition");
   is(textarea.value, "",
      "runCompositionCommitTest: textarea should become empty when replacing selection with empty string with composition");
@@ -1161,8 +1213,8 @@ function runCompositionCommitTest()
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "abc" });
 
-  is(result.length, 5,
-     "runCompositionCommitTest: 5 events should be fired when replacing selection with same string with composition");
+  is(result.length, 6,
+     "runCompositionCommitTest: 6 events should be fired when replacing selection with same string with composition");
   is(result[0].type, "compositionupdate",
      "runCompositionCommitTest: compositionupdate should be fired when replacing selection with same string with composition");
   is(result[1].type, "text",
@@ -1171,11 +1223,15 @@ function runCompositionCommitTest()
      "runCompositionCommitTest: beforeinput should be fired when replacing selection with same string with composition");
   checkInputEvent(result[2], true, "insertCompositionText", "abc", [],
                   "runCompositionCommitTest: when replacing selection with same string with composition");
-  is(result[3].type, "compositionend",
+  is(result[3].type, "textInput",
+     "runCompositionCommitTest: textInput should be fired when replacing selection with same string with composition");
+  checkTextInputEvent(result[3], "abc",
+                      "runCompositionCommitTest: when replacing selection with same string with composition");
+  is(result[4].type, "compositionend",
      "runCompositionCommitTest: compositionend should be fired when replacing selection with same string with composition");
-  is(result[4].type, "input",
+  is(result[5].type, "input",
      "runCompositionCommitTest: input should be fired when replacing selection with same string with composition");
-  checkInputEvent(result[4], false, "insertCompositionText", "abc", [],
+  checkInputEvent(result[5], false, "insertCompositionText", "abc", [],
                   "runCompositionCommitTest: when replacing selection with same string with composition");
   is(textarea.value, "abc",
      "runCompositionCommitTest: textarea should keep same value when replacing selection with same string with composition");
@@ -1198,8 +1254,8 @@ function runCompositionCommitTest()
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "", key: { key: "KEY_Enter" } });
 
-  is(result.length, 5,
-     "runCompositionCommitTest: 5 events should be fired after dispatching compositioncommit #4");
+  is(result.length, 6,
+     "runCompositionCommitTest: 6 events should be fired after dispatching compositioncommit #4");
   is(result[0].type, "compositionupdate",
      "runCompositionCommitTest: compositionupdate should be fired after dispatching compositioncommit #4");
   is(result[1].type, "text",
@@ -1208,11 +1264,15 @@ function runCompositionCommitTest()
      "runCompositionCommitTest: beforeinput should be fired after dispatching compositioncommit #4");
   checkInputEvent(result[2], true, "insertCompositionText", "", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #4");
-  is(result[3].type, "compositionend",
+  is(result[3].type, "textInput",
+     "runCompositionCommitTest: textInput should be fired after dispatching compositioncommit #4");
+  checkTextInputEvent(result[3], "",
+                      "runCompositionCommitTest: after dispatching compositioncommit #4");
+  is(result[4].type, "compositionend",
      "runCompositionCommitTest: compositionend should be fired after dispatching compositioncommit #4");
-  is(result[4].type, "input",
+  is(result[5].type, "input",
      "runCompositionCommitTest: input should be fired after dispatching compositioncommit #4");
-  checkInputEvent(result[4], false, "insertCompositionText", "", [],
+  checkInputEvent(result[5], false, "insertCompositionText", "", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #4");
   is(textarea.value, "", "runCompositionCommitTest: textarea should be empty #4");
 
@@ -1222,8 +1282,8 @@ function runCompositionCommitTest()
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "\u3042", key: { key: "a" } });
 
-  is(result.length, 5,
-     "runCompositionCommitTest: 5 events should be fired after dispatching compositioncommit #5");
+  is(result.length, 6,
+     "runCompositionCommitTest: 6 events should be fired after dispatching compositioncommit #5");
   is(result[0].type, "compositionupdate",
      "runCompositionCommitTest: compositionupdate should be fired after dispatching compositioncommit #5");
   is(result[1].type, "text",
@@ -1232,11 +1292,15 @@ function runCompositionCommitTest()
      "runCompositionCommitTest: beforeinput should be fired after dispatching compositioncommit #5");
   checkInputEvent(result[2], true, "insertCompositionText", "\u3042", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #5");
-  is(result[3].type, "compositionend",
+  is(result[3].type, "textInput",
+     "runCompositionCommitTest: textInput should be fired after dispatching compositioncommit #5");
+  checkTextInputEvent(result[3], "\u3042",
+                      "runCompositionCommitTest: after dispatching compositioncommit #5");
+  is(result[4].type, "compositionend",
      "runCompositionCommitTest: compositionend should be fired after dispatching compositioncommit #5");
-  is(result[4].type, "input",
+  is(result[5].type, "input",
      "runCompositionCommitTest: input should be fired after dispatching compositioncommit #5");
-  checkInputEvent(result[4], false, "insertCompositionText", "\u3042", [],
+  checkInputEvent(result[5], false, "insertCompositionText", "\u3042", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #5");
   is(textarea.value, "\u3042", "runCompositionCommitTest: textarea should be empty #5");
 
@@ -1258,24 +1322,29 @@ function runCompositionCommitTest()
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "\u3042", key: { key: "KEY_Enter" } });
 
-  is(result.length, 4,
-     "runCompositionCommitTest: 4 events should be fired after dispatching compositioncommit #6");
+  is(result.length, 5,
+     "runCompositionCommitTest: 5 events should be fired after dispatching compositioncommit #6");
   is(result[0].type, "text",
      "runCompositionCommitTest: text should be fired after dispatching compositioncommit #6");
   is(result[1].type, "beforeinput",
      "runCompositionCommitTest: beforeinput should be fired after dispatching compositioncommit #6");
   checkInputEvent(result[1], true, "insertCompositionText", "\u3042", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #6");
-  is(result[2].type, "compositionend",
+  is(result[2].type, "textInput",
+     "runCompositionCommitTest: textInput should be fired after dispatching compositioncommit #6");
+  checkTextInputEvent(result[2], "\u3042",
+                      "runCompositionCommitTest: after dispatching compositioncommit #6");
+  is(result[3].type, "compositionend",
      "runCompositionCommitTest: compositionend should be fired after dispatching compositioncommit #6");
-  is(result[3].type, "input",
+  is(result[4].type, "input",
      "runCompositionCommitTest: input should be fired after dispatching compositioncommit #6");
-  checkInputEvent(result[3], false, "insertCompositionText", "\u3042", [],
+  checkInputEvent(result[4], false, "insertCompositionText", "\u3042", [],
                   "runCompositionCommitTest: after dispatching compositioncommit #6");
   is(textarea.value, "\u3042", "runCompositionCommitTest: textarea should have committed string #6");
 
   // compositioncommit with same composition string when there is committed string
   textarea.value = "";
+  clearResult();
   synthesizeCompositionChange(
     { "composition":
       { "string": "\u3042",
@@ -1301,6 +1370,8 @@ function runCompositionCommitTest()
       "key": { key: "KEY_Enter", type: "keydown" },
     });
   is(textarea.value, "\u3042", "runCompositionCommitTest: textarea doesn't have composition string #6");
+  todo_isnot(result.findIndex(value => value.type == "textInput"), -1,
+             "runCompositionCommitTest: a textInput event should be fired before immediately commit #6");
 
   clearResult();
   synthesizeComposition({ type: "compositioncommit", data: "\u3042", key: { key: "KEY_Enter", type: "keyup" } });
@@ -1319,6 +1390,7 @@ function runCompositionCommitTest()
   textarea.removeEventListener("compositionupdate", handler, true);
   textarea.removeEventListener("compositionend", handler, true);
   textarea.removeEventListener("beforeinput", handler, true);
+  textarea.removeEventListener("textInput", handler, true);
   textarea.removeEventListener("input", handler, true);
   textarea.removeEventListener("text", handler, true);
 }
@@ -10860,6 +10932,10 @@ async function runInputModeTest()
 
 async function runTest()
 {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.events.textevent.enabled", true]],
+  });
+
   window.addEventListener("unload", window.arguments[0].SimpleTest.finish, {once: true, capture: true});
 
   contenteditable = document.getElementById("iframe4").contentDocument.getElementById("contenteditable");
diff --git a/widget/uikit/TextInputHandler.mm b/widget/uikit/TextInputHandler.mm
index 9a4a6ae226..3ee3573b83 100644
--- a/widget/uikit/TextInputHandler.mm
+++ b/widget/uikit/TextInputHandler.mm
@@ -10,6 +10,7 @@
 
 #include "mozilla/EventForwards.h"
 #include "mozilla/Logging.h"
+#include "mozilla/MacStringHelpers.h"
 #include "mozilla/MiscEvents.h"
 #include "mozilla/TextEventDispatcher.h"
 #include "mozilla/TextEvents.h"
@@ -23,21 +24,6 @@ mozilla::LazyLogModule gIMELog("TextInputHandler");
 
 namespace mozilla::widget {
 
-static void GetStringForNSString(const NSString* aSrc, nsAString& aDist) {
-  NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
-
-  if (!aSrc) {
-    aDist.Truncate();
-    return;
-  }
-
-  aDist.SetLength([aSrc length]);
-  [aSrc getCharacters:reinterpret_cast<unichar*>(aDist.BeginWriting())
-                range:NSMakeRange(0, [aSrc length])];
-
-  NS_OBJC_END_TRY_IGNORE_BLOCK;
-}
-
 NS_IMPL_ISUPPORTS(TextInputHandler, TextEventDispatcherListener,
                   nsISupportsWeakReference)
 
@@ -63,7 +49,7 @@ void TextInputHandler::WillDispatchKeyboardEvent(
 
 bool TextInputHandler::InsertText(NSString* aText) {
   nsString str;
-  GetStringForNSString(aText, str);
+  CopyNSStringToXPCOMString(aText, str);
 
   MOZ_LOG(gIMELog, LogLevel::Info,
           ("%p TextInputHandler::InsertText(aText=%s)", this,
diff --git a/widget/uikit/nsLookAndFeel.mm b/widget/uikit/nsLookAndFeel.mm
index b420cc9a1d..51a9a95b52 100644
--- a/widget/uikit/nsLookAndFeel.mm
+++ b/widget/uikit/nsLookAndFeel.mm
@@ -232,9 +232,6 @@ nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
     case IntID::CaretWidth:
       aResult = 1;
       break;
-    case IntID::ShowCaretDuringSelection:
-      aResult = 0;
-      break;
     case IntID::SelectTextfieldsOnKeyFocus:
       // Select textfield content when focused by kbd
       // used by nsEventStateManager::sTextfieldSelectModel
diff --git a/widget/windows/GfxInfo.cpp b/widget/windows/GfxInfo.cpp
index 0e1b4002d3..6d8429f1cc 100644
--- a/widget/windows/GfxInfo.cpp
+++ b/widget/windows/GfxInfo.cpp
@@ -310,7 +310,7 @@ uint32_t ParseIDFromDeviceID(const nsAString& key, const nsAString& prefix,
     return 0x5143;
   }
   nsresult err;
-  return id.ToInteger(&err, 16);
+  return id.ToUnsignedInteger(&err, 16);
 }
 
 // OS version in 16.16 major/minor form
diff --git a/widget/windows/ScreenHelperWin.cpp b/widget/windows/ScreenHelperWin.cpp
index 8a0ec3b608..945b8d1895 100644
--- a/widget/windows/ScreenHelperWin.cpp
+++ b/widget/windows/ScreenHelperWin.cpp
@@ -7,9 +7,12 @@
 #include "ScreenHelperWin.h"
 
 #include "mozilla/Logging.h"
+#include "mozilla/gfx/DeviceManagerDx.h"
 #include "nsTArray.h"
 #include "WinUtils.h"
 
+#include <dxgi.h>
+
 static mozilla::LazyLogModule sScreenLog("WidgetScreen");
 
 namespace mozilla {
@@ -74,8 +77,13 @@ static void GetDisplayInfo(const char16ptr_t aName,
   }
 }
 
+struct CollectMonitorsParam {
+  nsTArray<RefPtr<Screen>> screens;
+};
+
 BOOL CALLBACK CollectMonitors(HMONITOR aMon, HDC, LPRECT, LPARAM ioParam) {
-  auto screens = reinterpret_cast<nsTArray<RefPtr<Screen>>*>(ioParam);
+  CollectMonitorsParam* cmParam =
+      reinterpret_cast<CollectMonitorsParam*>(ioParam);
   BOOL success = FALSE;
   MONITORINFOEX info;
   info.cbSize = sizeof(MONITORINFOEX);
@@ -123,6 +131,9 @@ BOOL CALLBACK CollectMonitors(HMONITOR aMon, HDC, LPRECT, LPARAM ioParam) {
   GetDisplayInfo(info.szDevice, orientation, angle, isPseudoDisplay,
                  refreshRate);
 
+  auto* manager = gfx::DeviceManagerDx::Get();
+  bool isHDR = manager ? manager->MonitorHDREnabled(aMon) : false;
+
   MOZ_LOG(sScreenLog, LogLevel::Debug,
           ("New screen [%s (%s) %d %u %f %f %f %d %d %d]",
            ToString(rect).c_str(), ToString(availRect).c_str(), pixelDepth,
@@ -131,26 +142,32 @@ BOOL CALLBACK CollectMonitors(HMONITOR aMon, HDC, LPRECT, LPARAM ioParam) {
   auto screen = MakeRefPtr<Screen>(
       rect, availRect, pixelDepth, pixelDepth, refreshRate, contentsScaleFactor,
       defaultCssScaleFactor, dpi, Screen::IsPseudoDisplay(isPseudoDisplay),
-      orientation, angle);
+      Screen::IsHDR(isHDR), orientation, angle);
   if (info.dwFlags & MONITORINFOF_PRIMARY) {
     // The primary monitor must be the first element of the screen list.
-    screens->InsertElementAt(0, std::move(screen));
+    cmParam->screens.InsertElementAt(0, std::move(screen));
   } else {
-    screens->AppendElement(std::move(screen));
+    cmParam->screens.AppendElement(std::move(screen));
   }
   return TRUE;
 }
 
+/* static */
 void ScreenHelperWin::RefreshScreens() {
   MOZ_LOG(sScreenLog, LogLevel::Debug, ("Refreshing screens"));
 
-  AutoTArray<RefPtr<Screen>, 4> screens;
+  auto* manager = gfx::DeviceManagerDx::Get();
+  if (XRE_IsParentProcess() && manager) {
+    manager->UpdateMonitorInfo();
+  }
+
+  CollectMonitorsParam cmParam;
   BOOL result = ::EnumDisplayMonitors(
-      nullptr, nullptr, (MONITORENUMPROC)CollectMonitors, (LPARAM)&screens);
+      nullptr, nullptr, (MONITORENUMPROC)CollectMonitors, (LPARAM)&cmParam);
   if (!result) {
     NS_WARNING("Unable to EnumDisplayMonitors");
   }
-  ScreenManager::Refresh(std::move(screens));
+  ScreenManager::Refresh(std::move(cmParam.screens));
 }
 
 }  // namespace widget
diff --git a/widget/windows/WindowsSMTCProvider.cpp b/widget/windows/WindowsSMTCProvider.cpp
index 69915cafd8..3ddd26b6cc 100644
--- a/widget/windows/WindowsSMTCProvider.cpp
+++ b/widget/windows/WindowsSMTCProvider.cpp
@@ -356,7 +356,7 @@ bool WindowsSMTCProvider::RegisterEvents() {
 void WindowsSMTCProvider::OnButtonPressed(
     mozilla::dom::MediaControlKey aKey) const {
   if (!IsKeySupported(aKey)) {
-    LOG("key: %s is not supported", ToMediaControlKeyStr(aKey));
+    LOG("key: %s is not supported", dom::GetEnumString(aKey).get());
     return;
   }
 
@@ -383,7 +383,7 @@ bool WindowsSMTCProvider::UpdateButtons() {
   for (const mozilla::dom::MediaControlKey& key : kKeys) {
     if (!EnableKey(key, IsKeySupported(key))) {
       success = false;
-      LOG("Failed to set %s=%s", ToMediaControlKeyStr(key),
+      LOG("Failed to set %s=%s", dom::GetEnumString(key).get(),
           IsKeySupported(key) ? "true" : "false");
     }
   }
@@ -414,7 +414,7 @@ bool WindowsSMTCProvider::EnableKey(mozilla::dom::MediaControlKey aKey,
       // The callback for the event checks if the key is supported
       return mSeekRegistrationToken.value != 0;
     default:
-      LOG("No button for %s", ToMediaControlKeyStr(aKey));
+      LOG("No button for %s", dom::GetEnumString(aKey).get());
       return false;
   }
 }
diff --git a/widget/windows/moz.build b/widget/windows/moz.build
index f19a46caf1..eeda8d1257 100644
--- a/widget/windows/moz.build
+++ b/widget/windows/moz.build
@@ -39,6 +39,7 @@ EXPORTS += [
 ]
 
 EXPORTS.mozilla += [
+    "ScreenHelperWin.h",
     "ShellHeaderOnlyUtils.h",
     "ToastNotificationHeaderOnlyUtils.h",
     "UrlmonHeaderOnlyUtils.h",
diff --git a/widget/windows/nsFilePicker.cpp b/widget/windows/nsFilePicker.cpp
index fb4c6e80b5..2a45937988 100644
--- a/widget/windows/nsFilePicker.cpp
+++ b/widget/windows/nsFilePicker.cpp
@@ -735,7 +735,11 @@ nsFilePicker::CheckContentAnalysisService() {
     auto contentAnalysisCallback =
         mozilla::MakeRefPtr<mozilla::contentanalysis::ContentAnalysisCallback>(
             [promise](nsIContentAnalysisResponse* aResponse) {
-              promise->Resolve(aResponse->GetShouldAllowContent(), __func__);
+              bool shouldAllow = false;
+              mozilla::DebugOnly<nsresult> rv =
+                  aResponse->GetShouldAllowContent(&shouldAllow);
+              MOZ_ASSERT(NS_SUCCEEDED(rv));
+              promise->Resolve(shouldAllow, __func__);
             },
             [promise](nsresult aError) { promise->Reject(aError, __func__); });
 
@@ -840,7 +844,7 @@ nsresult nsFilePicker::Open(nsIFilePickerShownCallback* aCallback) {
   auto promise = mMode == modeGetFolder ? ShowFolderPicker(initialDir)
                                         : ShowFilePicker(initialDir);
 
-  auto p2 = promise->Then(
+  promise->Then(
       mozilla::GetMainThreadSerialEventTarget(), __PRETTY_FUNCTION__,
       [self = RefPtr(this),
        callback = RefPtr(aCallback)](bool selectionMade) -> void {
diff --git a/widget/windows/nsLookAndFeel.cpp b/widget/windows/nsLookAndFeel.cpp
index 6122000c9e..b6b6877857 100644
--- a/widget/windows/nsLookAndFeel.cpp
+++ b/widget/windows/nsLookAndFeel.cpp
@@ -36,6 +36,17 @@ static int32_t GetSystemParam(long flag, int32_t def) {
   return ::SystemParametersInfo(flag, 0, &value, 0) ? value : def;
 }
 
+static int32_t GetTooltipOffsetVertical() {
+  static constexpr DWORD kDefaultCursorSize = 32;
+  const DWORD cursorSize =
+      GetSystemParam(MOZ_SPI_CURSORSIZE, kDefaultCursorSize);
+  if (cursorSize == kDefaultCursorSize) {
+    return LookAndFeel::kDefaultTooltipOffset;
+  }
+  return std::ceilf(float(LookAndFeel::kDefaultTooltipOffset) *
+                    float(cursorSize) / float(kDefaultCursorSize));
+}
+
 static bool SystemWantsDarkTheme() {
   if (nsUXThemeData::IsHighContrastOn()) {
     return LookAndFeel::IsDarkColor(
@@ -353,6 +364,7 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme,
     case ColorID::Marktext:
     case ColorID::Mark:
     case ColorID::SpellCheckerUnderline:
+    case ColorID::MozAutofillBackground:
       aColor = GetStandinForNativeColor(aID, aScheme);
       return NS_OK;
     default:
@@ -392,13 +404,9 @@ nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
       aResult = std::ceil(float(timeout) / (2.0f * float(blinkTime)));
       break;
     }
-
     case IntID::CaretWidth:
       aResult = 1;
       break;
-    case IntID::ShowCaretDuringSelection:
-      aResult = 0;
-      break;
     case IntID::SelectTextfieldsOnKeyFocus:
       // Select textfield content when focused by kbd
       // used by EventStateManager::sTextfieldSelectModel
@@ -523,6 +531,9 @@ nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
     case IntID::ContextMenuOffsetHorizontal:
       aResult = 2;
       break;
+    case IntID::TooltipOffsetVertical:
+      aResult = GetTooltipOffsetVertical();
+      break;
     case IntID::SystemUsesDarkTheme:
       aResult = SystemWantsDarkTheme();
       break;
diff --git a/widget/windows/nsLookAndFeel.h b/widget/windows/nsLookAndFeel.h
index d19aa91329..0ef38bfda5 100644
--- a/widget/windows/nsLookAndFeel.h
+++ b/widget/windows/nsLookAndFeel.h
@@ -40,6 +40,10 @@
 #define SYS_COLOR_MAX 30
 #define SYS_COLOR_COUNT (SYS_COLOR_MAX - SYS_COLOR_MIN + 1)
 
+// Undocumented SPI, see bug 1712669 comment 4.
+#define MOZ_SPI_CURSORSIZE 0x2028
+#define MOZ_SPI_SETCURSORSIZE 0x2029
+
 namespace mozilla::widget::WinRegistry {
 class KeyWatcher;
 }
diff --git a/widget/windows/nsNativeThemeWin.cpp b/widget/windows/nsNativeThemeWin.cpp
index 04883a833f..7ef968baf6 100644
--- a/widget/windows/nsNativeThemeWin.cpp
+++ b/widget/windows/nsNativeThemeWin.cpp
@@ -484,9 +484,6 @@ mozilla::Maybe<nsUXThemeClass> nsNativeThemeWin::GetThemeClass(
     case StyleAppearance::Textfield:
     case StyleAppearance::Textarea:
       return Some(eUXEdit);
-    case StyleAppearance::Toolbox:
-      return Some(eUXRebar);
-    case StyleAppearance::Toolbar:
     case StyleAppearance::Toolbarbutton:
     case StyleAppearance::Separator:
       return Some(eUXToolbar);
@@ -719,27 +716,6 @@ nsresult nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame,
       }
       return NS_OK;
     }
-    case StyleAppearance::Toolbox: {
-      aState = 0;
-      aPart = RP_BACKGROUND;
-      return NS_OK;
-    }
-    case StyleAppearance::Toolbar: {
-      // Use -1 to indicate we don't wish to have the theme background drawn
-      // for this item. We will pass any nessessary information via aState,
-      // and will render the item using separate code.
-      aPart = -1;
-      aState = 0;
-      if (aFrame) {
-        nsIContent* content = aFrame->GetContent();
-        nsIContent* parent = content->GetParent();
-        // XXXzeniko hiding the first toolbar will result in an unwanted margin
-        if (parent && parent->GetFirstChild() == content) {
-          aState = 1;
-        }
-      }
-      return NS_OK;
-    }
     case StyleAppearance::Treeview:
     case StyleAppearance::Listbox: {
       aPart = TREEVIEW_BODY;
@@ -1031,16 +1007,6 @@ RENDER_AGAIN:
         ::DeleteObject(hPen);
       }
     }
-  } else if (aAppearance == StyleAppearance::Toolbar && state == 0) {
-    // Draw toolbar separator lines above all toolbars except the first one.
-    // The lines are part of the Rebar theme, which is loaded for
-    // StyleAppearance::Toolbox.
-    theme = GetTheme(StyleAppearance::Toolbox);
-    if (!theme) return NS_ERROR_FAILURE;
-
-    widgetRect.bottom = widgetRect.top + TB_SEPARATOR_HEIGHT;
-    DrawThemeEdge(theme, hdc, RP_BAND, 0, &widgetRect, EDGE_ETCHED, BF_TOP,
-                  nullptr);
   }
 
   nativeDrawing.EndNativeDrawing();
@@ -1101,7 +1067,6 @@ LayoutDeviceIntMargin nsNativeThemeWin::GetWidgetBorder(
   }
 
   if (!WidgetIsContainer(aAppearance) ||
-      aAppearance == StyleAppearance::Toolbox ||
       aAppearance == StyleAppearance::Tabpanel)
     return result;  // Don't worry about it.
 
@@ -1109,12 +1074,6 @@ LayoutDeviceIntMargin nsNativeThemeWin::GetWidgetBorder(
   nsresult rv = GetThemePartAndState(aFrame, aAppearance, part, state);
   if (NS_FAILED(rv)) return result;
 
-  if (aAppearance == StyleAppearance::Toolbar) {
-    // make space for the separator line above all toolbars but the first
-    if (state == 0) result.top = TB_SEPARATOR_HEIGHT;
-    return result;
-  }
-
   result = GetCachedWidgetBorder(theme, themeClass.value(), aAppearance, part,
                                  state);
 
@@ -1278,8 +1237,6 @@ LayoutDeviceIntSize nsNativeThemeWin::GetMinimumWidgetSize(
   switch (aAppearance) {
     case StyleAppearance::NumberInput:
     case StyleAppearance::Textfield:
-    case StyleAppearance::Toolbox:
-    case StyleAppearance::Toolbar:
     case StyleAppearance::Progresschunk:
     case StyleAppearance::Tabpanels:
     case StyleAppearance::Tabpanel:
@@ -1352,9 +1309,7 @@ nsNativeThemeWin::WidgetStateChanged(nsIFrame* aFrame,
                                      nsAtom* aAttribute, bool* aShouldRepaint,
                                      const nsAttrValue* aOldValue) {
   // Some widget types just never change state.
-  if (aAppearance == StyleAppearance::Toolbox ||
-      aAppearance == StyleAppearance::Toolbar ||
-      aAppearance == StyleAppearance::Progresschunk ||
+  if (aAppearance == StyleAppearance::Progresschunk ||
       aAppearance == StyleAppearance::ProgressBar ||
       aAppearance == StyleAppearance::Tabpanels ||
       aAppearance == StyleAppearance::Tabpanel ||
diff --git a/widget/windows/nsUXThemeData.cpp b/widget/windows/nsUXThemeData.cpp
index b3f9e6fce9..ce8b0f3479 100644
--- a/widget/windows/nsUXThemeData.cpp
+++ b/widget/windows/nsUXThemeData.cpp
@@ -62,8 +62,6 @@ const wchar_t* nsUXThemeData::GetClassName(nsUXThemeClass cls) {
       return L"Button";
     case eUXEdit:
       return L"Edit";
-    case eUXRebar:
-      return L"Rebar";
     case eUXToolbar:
       return L"Toolbar";
     case eUXProgress:
diff --git a/widget/windows/nsUXThemeData.h b/widget/windows/nsUXThemeData.h
index 38be8b4484..24fe07d128 100644
--- a/widget/windows/nsUXThemeData.h
+++ b/widget/windows/nsUXThemeData.h
@@ -19,7 +19,6 @@
 enum nsUXThemeClass {
   eUXButton = 0,
   eUXEdit,
-  eUXRebar,
   eUXToolbar,
   eUXProgress,
   eUXTab,
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index b304d2efac..22d20d099e 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -78,6 +78,7 @@
 #include <limits>
 
 #include "mozilla/widget/WinMessages.h"
+#include "nsLookAndFeel.h"
 #include "nsWindow.h"
 #include "nsWindowTaskbarConcealer.h"
 #include "nsAppRunner.h"
@@ -181,11 +182,13 @@
 #  endif
 #  include "mozilla/a11y/Compatibility.h"
 #  include "oleidl.h"
+#  include <uiautomation.h>
 #  include <winuser.h>
 #  include "nsAccessibilityService.h"
 #  include "mozilla/a11y/DocAccessible.h"
 #  include "mozilla/a11y/LazyInstantiator.h"
 #  include "mozilla/a11y/Platform.h"
+#  include "mozilla/StaticPrefs_accessibility.h"
 #  if !defined(WINABLEAPI)
 #    include <winable.h>
 #  endif  // !defined(WINABLEAPI)
@@ -1335,8 +1338,6 @@ DWORD nsWindow::WindowExStyle() {
       }
       return extendedStyle;
     }
-    case WindowType::Sheet:
-      MOZ_FALLTHROUGH_ASSERT("Sheets are macOS specific");
     case WindowType::Dialog:
     case WindowType::TopLevel:
     case WindowType::Invisible:
@@ -1583,13 +1584,6 @@ void nsWindow::Show(bool bState) {
   // SetWindowPos would get the correct answer.
   mIsVisible = bState;
 
-  // We may have cached an out of date visible state. This can happen
-  // when session restore sets the full screen mode.
-  if (mIsVisible)
-    mOldStyle |= WS_VISIBLE;
-  else
-    mOldStyle &= ~WS_VISIBLE;
-
   if (mWnd) {
     if (bState) {
       if (!wasVisible && mWindowType == WindowType::TopLevel) {
@@ -2043,13 +2037,6 @@ void nsWindow::Resize(double aX, double aY, double aWidth, double aHeight,
   if (aRepaint) Invalidate();
 }
 
-mozilla::Maybe<bool> nsWindow::IsResizingNativeWidget() {
-  if (mResizeState == RESIZING) {
-    return Some(true);
-  }
-  return Some(false);
-}
-
 /**************************************************************
  *
  * SECTION: Window Z-order and state.
@@ -3070,34 +3057,85 @@ void nsWindow::HideWindowChrome(bool aShouldHide) {
 
   if (mHideChrome == aShouldHide) return;
 
-  DWORD_PTR style, exStyle;
-  mHideChrome = aShouldHide;
-  if (aShouldHide) {
-    DWORD_PTR tempStyle = ::GetWindowLongPtrW(hwnd, GWL_STYLE);
-    DWORD_PTR tempExStyle = ::GetWindowLongPtrW(hwnd, GWL_EXSTYLE);
+  // Data manipulation: styles + ex-styles, and bitmasking operations thereupon.
+  struct Styles {
+    LONG_PTR style, ex;
+    constexpr Styles operator|(Styles const& that) const {
+      return Styles{.style = style | that.style, .ex = ex | that.ex};
+    }
+    constexpr Styles operator&(Styles const& that) const {
+      return Styles{.style = style & that.style, .ex = ex & that.ex};
+    }
+    constexpr Styles operator~() const {
+      return Styles{.style = ~style, .ex = ~ex};
+    }
 
-    style = tempStyle & ~(WS_CAPTION | WS_THICKFRAME);
-    exStyle = tempExStyle & ~(WS_EX_DLGMODALFRAME | WS_EX_WINDOWEDGE |
-                              WS_EX_CLIENTEDGE | WS_EX_STATICEDGE);
+    // Compute a style-set which matches `zero` where the bits of `this` are 0
+    // and `one` where the bits of `this` are 1.
+    constexpr Styles merge(Styles zero, Styles one) const {
+      Styles const& mask = *this;
+      return (~mask & zero) | (mask & one);
+    }
 
-    mOldStyle = tempStyle;
-    mOldExStyle = tempExStyle;
-  } else {
-    if (!mOldStyle || !mOldExStyle) {
-      mOldStyle = ::GetWindowLongPtrW(hwnd, GWL_STYLE);
-      mOldExStyle = ::GetWindowLongPtrW(hwnd, GWL_EXSTYLE);
+    // The dual of `merge`, above: returns a pair [zero, one] satisfying
+    // `a.merge(a.split(b)...) == b`. (Or its equivalent in valid C++.)
+    constexpr std::tuple<Styles, Styles> split(Styles data) const {
+      Styles const& mask = *this;
+      return {~mask & data, mask & data};
     }
+  };
 
-    style = mOldStyle;
-    exStyle = mOldExStyle;
+  // Get styles from an HWND.
+  constexpr auto const GetStyles = [](HWND hwnd) {
+    return Styles{.style = ::GetWindowLongPtrW(hwnd, GWL_STYLE),
+                  .ex = ::GetWindowLongPtrW(hwnd, GWL_EXSTYLE)};
+  };
+  constexpr auto const SetStyles = [](HWND hwnd, Styles styles) {
+    VERIFY_WINDOW_STYLE(styles.style);
+    ::SetWindowLongPtrW(hwnd, GWL_STYLE, styles.style);
+    ::SetWindowLongPtrW(hwnd, GWL_EXSTYLE, styles.ex);
+  };
+
+  // Get styles from *this.
+  auto const GetCachedStyles = [&]() {
+    return mOldStyles.map([](auto const& m) {
+      return Styles{.style = m.style, .ex = m.exStyle};
+    });
+  };
+  auto const SetCachedStyles = [&](Styles styles) {
+    using WStyles = nsWindow::WindowStyles;
+    mOldStyles = Some(WStyles{.style = styles.style, .exStyle = styles.ex});
+  };
+
+  // The mask describing the "chrome" which this function is supposed to remove
+  // (or restore, as the case may be). Other style-flags will be left untouched.
+  constexpr static const Styles kChromeMask{
+      .style = WS_CAPTION | WS_THICKFRAME,
+      .ex = WS_EX_DLGMODALFRAME | WS_EX_WINDOWEDGE | WS_EX_CLIENTEDGE |
+            WS_EX_STATICEDGE};
+
+  // The desired style-flagset for fullscreen windows. (This happens to be all
+  // zeroes, but we don't need to rely on that.)
+  constexpr static const Styles kFullscreenChrome{.style = 0, .ex = 0};
+
+  auto const [chromeless, currentChrome] = kChromeMask.split(GetStyles(hwnd));
+  Styles newChrome{}, oldChrome{};
+
+  mHideChrome = aShouldHide;
+  if (aShouldHide) {
+    newChrome = kFullscreenChrome;
+    oldChrome = currentChrome;
+  } else {
+    // if there's nothing to "restore" it to, just use what's there now
+    oldChrome = GetCachedStyles().refOr(currentChrome);
+    newChrome = oldChrome;
     if (mFutureMarginsToUse) {
       SetNonClientMargins(mFutureMarginsOnceChromeShows);
     }
   }
 
-  VERIFY_WINDOW_STYLE(style);
-  ::SetWindowLongPtrW(hwnd, GWL_STYLE, style);
-  ::SetWindowLongPtrW(hwnd, GWL_EXSTYLE, exStyle);
+  SetCachedStyles(oldChrome);
+  SetStyles(hwnd, kChromeMask.merge(chromeless, newChrome));
 }
 
 /**************************************************************
@@ -4941,10 +4979,12 @@ bool nsWindow::ProcessMessageInternal(UINT msg, WPARAM& wParam, LPARAM& lParam,
 
     case WM_SETTINGCHANGE: {
       if (wParam == SPI_SETCLIENTAREAANIMATION ||
-          wParam == SPI_SETKEYBOARDDELAY || wParam == SPI_SETMOUSEVANISH) {
+          wParam == SPI_SETKEYBOARDDELAY || wParam == SPI_SETMOUSEVANISH ||
+          wParam == MOZ_SPI_SETCURSORSIZE) {
         // These need to update LookAndFeel cached values.
         // They affect reduced motion settings / caret blink count / show
-        // pointer while typing, so no need to invalidate style / layout.
+        // pointer while typing / tooltip offset, so no need to invalidate style
+        // / layout.
         NotifyThemeChanged(widget::ThemeChangeKind::MediaQueriesOnly);
         break;
       }
@@ -5885,6 +5925,20 @@ bool nsWindow::ProcessMessageInternal(UINT msg, WPARAM& wParam, LPARAM& lParam,
           a11y::LazyInstantiator::EnableBlindAggregation(mWnd);
           result = true;
         }
+      } else if (objId == UiaRootObjectId &&
+                 StaticPrefs::accessibility_uia_enable()) {
+        if (a11y::LocalAccessible* acc = GetAccessible()) {
+          RefPtr<IAccessible> ia;
+          acc->GetNativeInterface(getter_AddRefs(ia));
+          MOZ_ASSERT(ia);
+          RefPtr<IRawElementProviderSimple> uia;
+          ia->QueryInterface(IID_IRawElementProviderSimple,
+                             getter_AddRefs(uia));
+          if (uia) {
+            *aRetValue = UiaReturnRawElementProvider(mWnd, wParam, lParam, uia);
+            result = true;
+          }
+        }
       }
     } break;
 #endif
diff --git a/widget/windows/nsWindow.h b/widget/windows/nsWindow.h
index 3a521fb978..a2b2a701bd 100644
--- a/widget/windows/nsWindow.h
+++ b/widget/windows/nsWindow.h
@@ -175,7 +175,6 @@ class nsWindow final : public nsBaseWidget {
   void Resize(double aWidth, double aHeight, bool aRepaint) override;
   void Resize(double aX, double aY, double aWidth, double aHeight,
               bool aRepaint) override;
-  mozilla::Maybe<bool> IsResizingNativeWidget() override;
   void PlaceBehind(nsTopLevelWidgetZPlacement aPlacement, nsIWidget* aWidget,
                    bool aActivate) override;
   void SetSizeMode(nsSizeMode aMode) override;
@@ -755,8 +754,12 @@ class nsWindow final : public nsBaseWidget {
   bool mIsAlert = false;
   bool mIsPerformingDwmFlushHack = false;
   bool mDraggingWindowWithMouse = false;
-  DWORD_PTR mOldStyle = 0;
-  DWORD_PTR mOldExStyle = 0;
+  // Partial cached window-styles, for when going fullscreen. (Only window-
+  // decoration-related flags are saved here.)
+  struct WindowStyles {
+    LONG_PTR style, exStyle;
+  };
+  mozilla::Maybe<WindowStyles> mOldStyles;
   nsNativeDragTarget* mNativeDragTarget = nullptr;
   HKL mLastKeyboardLayout = 0;
   mozilla::CheckInvariantWrapper<FrameState> mFrameState;