Merge pull request 'Resolve various issues on Big Sur' (#1685) from dbsoft/UXP:master into master

Reviewed-on: https://repo.palemoon.org/MoonchildProductions/UXP/pulls/1685

12 files changed, 328 insertions, 615 deletions

diff --git a/memory/mozjemalloc/jemalloc.c b/memory/mozjemalloc/jemalloc.c
index 86864e1cd0..0eb5241c78 100644
--- a/memory/mozjemalloc/jemalloc.c
+++ b/memory/mozjemalloc/jemalloc.c
@@ -302,6 +302,9 @@ typedef long ssize_t;
 #include <mach/mach_init.h>
 #include <mach/vm_map.h>
 #include <malloc/malloc.h>
+#ifndef _pthread_self
+#define _pthread_self() pthread_self()
+#endif
 #endif
 
 #endif
diff --git a/nsprpub/pr/src/linking/prlink.c b/nsprpub/pr/src/linking/prlink.c
index 1f3430714e..4e73d9df1c 100644
--- a/nsprpub/pr/src/linking/prlink.c
+++ b/nsprpub/pr/src/linking/prlink.c
@@ -776,6 +776,9 @@ pr_LoadLibraryByPathname(const char *name, PRIntn flags)
         int dl_flags = 0;
 #endif
         void *h = NULL;
+#if defined(DARWIN)
+        PRBool okToLoad = PR_FALSE;
+#endif
 
         if (flags & PR_LD_LAZY) {
             dl_flags |= RTLD_LAZY;
@@ -790,12 +793,36 @@ pr_LoadLibraryByPathname(const char *name, PRIntn flags)
             dl_flags |= RTLD_LOCAL;
         }
 #if defined(DARWIN)
-        /* ensure the file exists if it contains a slash character i.e. path */
-        /* DARWIN's dlopen ignores the provided path and checks for the */
-        /* plain filename in DYLD_LIBRARY_PATH */
-        if (strchr(name, PR_DIRECTORY_SEPARATOR) == NULL ||
-            PR_Access(name, PR_ACCESS_EXISTS) == PR_SUCCESS) {
-            h = dlopen(name, dl_flags);
+        /* If the file contains an absolute or relative path (slash)
+         * and the path doesn't look like a System path, then require
+         * the file exists.
+         * The reason is that DARWIN's dlopen ignores the provided path
+         * and checks for the plain filename in DYLD_LIBRARY_PATH,
+         * which could load an unexpected version of a library. */
+        if (strchr(name, PR_DIRECTORY_SEPARATOR) == NULL) {
+          /* no slash, allow to load from any location */
+          okToLoad = PR_TRUE;
+        } else {
+          const char systemPrefix1[] = "/System/";
+          const size_t systemPrefixLen1 = strlen(systemPrefix1);
+          const char systemPrefix2[] = "/usr/lib/";
+          const size_t systemPrefixLen2 = strlen(systemPrefix2);
+          const name_len = strlen(name);
+          if (((name_len > systemPrefixLen1) &&
+               (strncmp(name, systemPrefix1, systemPrefixLen1) == 0)) ||
+             ((name_len > systemPrefixLen2) &&
+               (strncmp(name, systemPrefix2, systemPrefixLen2) == 0))) {
+            /* found at beginning, it's a system library.
+             * Skip filesystem check (required for macOS 11),
+             * allow loading from any location */
+            okToLoad = PR_TRUE;
+          } else if (PR_Access(name, PR_ACCESS_EXISTS) == PR_SUCCESS) {
+            /* file exists, allow to load */
+            okToLoad = PR_TRUE;
+          }
+        }
+        if (okToLoad) {
+          h = dlopen(name, dl_flags);
         }
 #else
         h = dlopen(name, dl_flags);
diff --git a/widget/cocoa/VibrancyManager.h b/widget/cocoa/VibrancyManager.h
index baaa20f689..04b1ad1cda 100644
--- a/widget/cocoa/VibrancyManager.h
+++ b/widget/cocoa/VibrancyManager.h
@@ -77,14 +77,6 @@ public:
   bool HasVibrantRegions() { return !mVibrantRegions.IsEmpty(); }
 
   /**
-   * Clear the vibrant areas that we know about.
-   * The clearing happens in the current NSGraphicsContext. If you call this
-   * from within an -[NSView drawRect:] implementation, the currrent
-   * NSGraphicsContext is already correctly set to the window drawing context.
-   */
-  void ClearVibrantAreas() const;
-
-  /**
    * Return the fill color that should be drawn on top of the cleared window
    * parts. Usually this would be drawn by -[NSVisualEffectView drawRect:].
    * The returned color is opaque if the system-wide "Reduce transparency"
@@ -105,10 +97,19 @@ public:
    */
   static bool SystemSupportsVibrancy();
 
-protected:
-  void ClearVibrantRegion(const LayoutDeviceIntRegion& aVibrantRegion) const;
-  NSView* CreateEffectView(VibrancyType aType);
+  /**
+   * Create an NSVisualEffectView for the specified vibrancy type. The return
+   * value is not autoreleased. We return an object of type NSView* because we
+   * compile with an SDK that does not contain a definition for
+   * NSVisualEffectView.
+   * @param aIsContainer Whether this NSView will have child views. This value
+   *                     affects hit testing: Container views will pass through
+   *                     hit testing requests to their children, and leaf views
+   *                     will be transparent to hit testing.
+   */
+  static NSView* CreateEffectView(VibrancyType aType, BOOL aIsContainer = NO);
 
+protected:
   const nsChildView& mCoordinateConverter;
   NSView* mContainerView;
   nsClassHashtable<nsUint32HashKey, ViewRegion> mVibrantRegions;
diff --git a/widget/cocoa/VibrancyManager.mm b/widget/cocoa/VibrancyManager.mm
index 619dc969f6..d02338eb6b 100644
--- a/widget/cocoa/VibrancyManager.mm
+++ b/widget/cocoa/VibrancyManager.mm
@@ -23,24 +23,6 @@ VibrancyManager::UpdateVibrantRegion(VibrancyType aType,
   });
 }
 
-void
-VibrancyManager::ClearVibrantAreas() const
-{
-  for (auto iter = mVibrantRegions.ConstIter(); !iter.Done(); iter.Next()) {
-    ClearVibrantRegion(iter.UserData()->Region());
-  }
-}
-
-void
-VibrancyManager::ClearVibrantRegion(const LayoutDeviceIntRegion& aVibrantRegion) const
-{
-  [[NSColor clearColor] set];
-
-  for (auto iter = aVibrantRegion.RectIter(); !iter.Done(); iter.Next()) {
-    NSRectFill(mCoordinateConverter.DevPixelsToCocoaPoints(iter.Get()));
-  }
-}
-
 @interface NSView(CurrentFillColor)
 - (NSColor*)_currentFillColor;
 @end
@@ -64,9 +46,8 @@ VibrancyManager::VibrancyFillColorForType(VibrancyType aType)
   NSView* view = mVibrantRegions.LookupOrAdd(uint32_t(aType))->GetAnyView();
 
   if (view && [view respondsToSelector:@selector(_currentFillColor)]) {
-    // -[NSVisualEffectView _currentFillColor] is the color that our view
-    // would draw during its drawRect implementation, if we hadn't
-    // disabled that.
+    // -[NSVisualEffectView _currentFillColor] is the color that the view
+    // draws in its drawRect implementation.
     return AdjustedColor([view _currentFillColor], aType);
   }
   return [NSColor whiteColor];
@@ -87,19 +68,6 @@ VibrancyManager::VibrancyFontSmoothingBackgroundColorForType(VibrancyType aType)
   return [NSColor clearColor];
 }
 
-static void
-DrawRectNothing(id self, SEL _cmd, NSRect aRect)
-{
-  // The super implementation would clear the background.
-  // That's fine for views that are placed below their content, but our
-  // setup is different: Our drawn content is drawn to mContainerView, which
-  // sits below this EffectView. So we must not clear the background here,
-  // because we'd erase that drawn content.
-  // Of course the regular content drawing still needs to clear the background
-  // behind vibrant areas. This is taken care of by having nsNativeThemeCocoa
-  // return true from NeedToClearBackgroundBehindWidget for vibrant widgets.
-}
-
 static NSView*
 HitTestNil(id self, SEL _cmd, NSPoint aPoint)
 {
@@ -115,21 +83,20 @@ AllowsVibrancyYes(id self, SEL _cmd)
 }
 
 static Class
-CreateEffectViewClass(BOOL aForegroundVibrancy)
+CreateEffectViewClass(BOOL aForegroundVibrancy, BOOL aIsContainer)
 {
-  // Create a class called EffectView that inherits from NSVisualEffectView
-  // and overrides the methods -[NSVisualEffectView drawRect:] and
-  // -[NSView hitTest:].
+  // Create a class that inherits from NSVisualEffectView and overrides the
+  // methods -[NSView hitTest:] and  -[NSVisualEffectView allowsVibrancy].
   Class NSVisualEffectViewClass = NSClassFromString(@"NSVisualEffectView");
   const char* className = aForegroundVibrancy
     ? "EffectViewWithForegroundVibrancy" : "EffectViewWithoutForegroundVibrancy";
   Class EffectViewClass = objc_allocateClassPair(NSVisualEffectViewClass, className, 0);
-  class_addMethod(EffectViewClass, @selector(drawRect:), (IMP)DrawRectNothing,
-                  "v@:{CGRect={CGPoint=dd}{CGSize=dd}}");
-  class_addMethod(EffectViewClass, @selector(hitTest:), (IMP)HitTestNil,
-                  "@@:{CGPoint=dd}");
+  if (!aIsContainer) {
+    class_addMethod(EffectViewClass, @selector(hitTest:), (IMP)HitTestNil,
+                    "@@:{CGPoint=dd}");
+  }
   if (aForegroundVibrancy) {
-    // Also override the -[NSView allowsVibrancy] method to return YES.
+    // Override the -[NSView allowsVibrancy] method to return YES.
     class_addMethod(EffectViewClass, @selector(allowsVibrancy), (IMP)AllowsVibrancyYes, "I@:");
   }
   return EffectViewClass;
@@ -216,13 +183,20 @@ enum {
 @end
 
 NSView*
-VibrancyManager::CreateEffectView(VibrancyType aType)
-{
-  static Class EffectViewClassWithoutForegroundVibrancy = CreateEffectViewClass(NO);
-  static Class EffectViewClassWithForegroundVibrancy = CreateEffectViewClass(YES);
-
-  Class EffectViewClass = HasVibrantForeground(aType)
-    ? EffectViewClassWithForegroundVibrancy : EffectViewClassWithoutForegroundVibrancy;
+VibrancyManager::CreateEffectView(VibrancyType aType, BOOL aIsContainer)
+{
+  static Class EffectViewWithoutForegroundVibrancy = CreateEffectViewClass(NO, NO);
+  static Class EffectViewWithForegroundVibrancy = CreateEffectViewClass(YES, NO);
+  static Class EffectViewContainer = CreateEffectViewClass(NO, YES);
+
+  // Pick the right NSVisualEffectView subclass for the desired vibrancy mode.
+  // For "container" views, never use foreground vibrancy, because returning
+  // YES from allowsVibrancy forces on foreground vibrancy for all descendant
+  // views which can have unintended effects.
+  Class EffectViewClass = aIsContainer
+                              ? EffectViewContainer
+                              : (HasVibrantForeground(aType) ? EffectViewWithForegroundVibrancy
+                                                             : EffectViewWithoutForegroundVibrancy);
   NSView* effectView = [[EffectViewClass alloc] initWithFrame:NSZeroRect];
   [effectView performSelector:@selector(setAppearance:)
                    withObject:AppearanceForVibrancyType(aType)];
diff --git a/widget/cocoa/mozView.h b/widget/cocoa/mozView.h
index 9e94e3ab4c..bd054893ba 100644
--- a/widget/cocoa/mozView.h
+++ b/widget/cocoa/mozView.h
@@ -34,11 +34,6 @@ class TextInputHandler;
   // return a context menu for this view
 - (NSMenu*)contextMenu;
 
-  // Allows callers to do a delayed invalidate (e.g., if an invalidate
-  // happens during drawing)
-- (void)setNeedsPendingDisplay;
-- (void)setNeedsPendingDisplayInRect:(NSRect)invalidRect;
-
   // called when our corresponding Gecko view goes away
 - (void)widgetDestroyed;
 
diff --git a/widget/cocoa/nsChildView.h b/widget/cocoa/nsChildView.h
index f6fb44633c..2817c8d415 100644
--- a/widget/cocoa/nsChildView.h
+++ b/widget/cocoa/nsChildView.h
@@ -56,6 +56,8 @@ class WidgetRenderingContext;
 } // namespace widget
 } // namespace mozilla
 
+@class PixelHostingView;
+
 @interface NSEvent (Undocumented)
 
 // Return Cocoa event's corresponding Carbon event.  Not initialized (on
@@ -139,11 +141,6 @@ class WidgetRenderingContext;
   // when acceptsFirstMouse: is called, we store the event here (strong)
   NSEvent* mClickThroughMouseDownEvent;
 
-  // rects that were invalidated during a draw, so have pending drawing
-  NSMutableArray* mPendingDirtyRects;
-  BOOL mPendingFullDisplay;
-  BOOL mPendingDisplay;
-
   // WheelStart/Stop events should always come in pairs. This BOOL records the
   // last received event so that, when we receive one of the events, we make sure
   // to send its pair event first, in case we didn't yet for any reason.
@@ -185,8 +182,6 @@ class WidgetRenderingContext;
   float mCumulativeMagnification;
   float mCumulativeRotation;
 
-  BOOL mWaitingForPaint;
-
 #ifdef __LP64__
   // Support for fluid swipe tracking.
   BOOL* mCancelSwipeAnimation;
@@ -198,6 +193,15 @@ class WidgetRenderingContext;
   // The mask image that's used when painting into the titlebar using basic
   // CGContext painting (i.e. non-accelerated).
   CGImageRef mTopLeftCornerMask;
+
+  // Subviews of self, which act as container views for vibrancy views and
+  // non-draggable views.
+  NSView* mVibrancyViewsContainer;      // [STRONG]
+  NSView* mNonDraggableViewsContainer;  // [STRONG]
+
+  // The view that does our drawing. This is a subview of self so that it can
+  // be ordered on top of mVibrancyViewsContainer.
+  PixelHostingView* mPixelHostingView;
 }
 
 // class initialization
@@ -226,6 +230,10 @@ class WidgetRenderingContext;
 - (bool)preRender:(NSOpenGLContext *)aGLContext;
 - (void)postRender:(NSOpenGLContext *)aGLContext;
 
+- (NSView*)vibrancyViewsContainer;
+- (NSView*)nonDraggableViewsContainer;
+- (NSView*)pixelHostingView;
+
 - (BOOL)isCoveringTitlebar;
 
 - (void)viewWillStartLiveResize;
@@ -252,7 +260,6 @@ class WidgetRenderingContext;
 - (void)endGestureWithEvent:(NSEvent *)anEvent;
 
 - (void)scrollWheel:(NSEvent *)anEvent;
-- (void)handleAsyncScrollEvent:(CGEventRef)cgEvent ofType:(CGEventType)type;
 
 - (void)setUsingOMTCompositor:(BOOL)aUseOMTC;
 
@@ -507,8 +514,6 @@ public:
   void CleanupRemoteDrawing() override;
   bool InitCompositor(mozilla::layers::Compositor* aCompositor) override;
 
-  IAPZCTreeManager* APZCTM() { return mAPZC ; }
-
   NS_IMETHOD StartPluginIME(const mozilla::WidgetKeyboardEvent& aKeyboardEvent,
                             int32_t aPanelX, int32_t aPanelY,
                             nsString& aCommitted) override;
@@ -529,9 +534,6 @@ protected:
   void              ReportMoveEvent();
   void              ReportSizeEvent();
 
-  // override to create different kinds of child views. Autoreleases, so
-  // caller must retain.
-  virtual NSView*   CreateCocoaView(NSRect inFrame);
   void              TearDownView();
 
   virtual already_AddRefed<nsIWidget>
@@ -574,7 +576,7 @@ protected:
 
 protected:
 
-  NSView<mozView>*      mView;      // my parallel cocoa view (ChildView or NativeScrollbarView), [STRONG]
+  ChildView<mozView>* mView;  // my parallel cocoa view, [STRONG]
   RefPtr<mozilla::widget::TextInputHandler> mTextInputHandler;
   InputContext          mInputContext;
 
diff --git a/widget/cocoa/nsChildView.mm b/widget/cocoa/nsChildView.mm
index 1a257d899d..868687fe16 100644
--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -146,7 +146,10 @@ bool gUserCancelledDrag = false;
 
 uint32_t nsChildView::sLastInputEventCount = 0;
 
-static uint32_t gNumberOfWidgetsNeedingEventThread = 0;
+// The view that will do our drawing or host our NSOpenGLContext or Core Animation layer.
+@interface PixelHostingView : NSView {
+}
+@end
 
 @interface ChildView(Private)
 
@@ -163,14 +166,9 @@ static uint32_t gNumberOfWidgetsNeedingEventThread = 0;
 
 - (BOOL)isRectObscuredBySubview:(NSRect)inRect;
 
-- (void)processPendingRedraws;
-
-- (void)drawRect:(NSRect)aRect inContext:(CGContextRef)aContext;
 - (LayoutDeviceIntRegion)nativeDirtyRegionWithBoundingRect:(NSRect)aRect;
-- (BOOL)isUsingMainThreadOpenGL;
 - (BOOL)isUsingOpenGL;
 - (void)drawUsingOpenGL;
-- (void)drawUsingOpenGLCallback;
 
 - (BOOL)hasRoundedBottomCorners;
 - (CGFloat)cornerRadius;
@@ -195,7 +193,6 @@ static uint32_t gNumberOfWidgetsNeedingEventThread = 0;
 
 - (LayoutDeviceIntPoint)convertWindowCoordinates:(NSPoint)aPoint;
 - (LayoutDeviceIntPoint)convertWindowCoordinatesRoundDown:(NSPoint)aPoint;
-- (IAPZCTreeManager*)apzctm;
 
 - (BOOL)inactiveWindowAcceptsMouseEvent:(NSEvent*)aEvent;
 - (void)updateWindowDraggableState;
@@ -204,26 +201,10 @@ static uint32_t gNumberOfWidgetsNeedingEventThread = 0;
 
 @end
 
-@interface EventThreadRunner : NSObject
-{
-  NSThread* mThread;
-}
-- (id)init;
-
-+ (void)start;
-+ (void)stop;
-
-@end
-
 @interface NSView(NSThemeFrameCornerRadius)
 - (float)roundedCornerRadius;
 @end
 
-@interface NSView(DraggableRegion)
-- (CGSRegionObj)_regionForOpaqueDescendants:(NSRect)aRect forMove:(BOOL)aForMove;
-- (CGSRegionObj)_regionForOpaqueDescendants:(NSRect)aRect forMove:(BOOL)aForMove forUnderTitlebar:(BOOL)aForUnderTitlebar;
-@end
-
 @interface NSWindow(NSWindowShouldZoomOnDoubleClick)
 + (BOOL)_shouldZoomOnDoubleClick; // present on 10.7 and above
 @end
@@ -380,13 +361,6 @@ nsChildView::~nsChildView()
 
   DestroyCompositor();
 
-  if (mAPZC && gfxPrefs::AsyncPanZoomSeparateEventThread()) {
-    gNumberOfWidgetsNeedingEventThread--;
-    if (gNumberOfWidgetsNeedingEventThread == 0) {
-      [EventThreadRunner stop];
-    }
-  }
-
   // An nsChildView object that was in use can be destroyed without Destroy()
   // ever being called on it.  So we also need to do a quick, safe cleanup
   // here (it's too late to just call Destroy(), which can cause crashes).
@@ -455,7 +429,8 @@ nsChildView::Create(nsIWidget* aParent,
   // that NS_NATIVE_WIDGET is the NSView.
   CGFloat scaleFactor = nsCocoaUtils::GetBackingScaleFactor(mParentView);
   NSRect r = nsCocoaUtils::DevPixelsToCocoaPoints(mBounds, scaleFactor);
-  mView = [(NSView<mozView>*)CreateCocoaView(r) retain];
+  mView = [[[[ChildView alloc] initWithFrame:r geckoChild:this] autorelease] retain];
+  
   if (!mView) {
     return NS_ERROR_FAILURE;
   }
@@ -488,17 +463,6 @@ nsChildView::Create(nsIWidget* aParent,
   NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
 }
 
-// Creates the appropriate child view. Override to create something other than
-// our |ChildView| object. Autoreleases, so caller must retain.
-NSView*
-nsChildView::CreateCocoaView(NSRect inFrame)
-{
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;
-
-  return [[[ChildView alloc] initWithFrame:inFrame geckoChild:this] autorelease];
-
-  NS_OBJC_END_TRY_ABORT_BLOCK_NIL;
-}
 
 void nsChildView::TearDownView()
 {
@@ -982,8 +946,9 @@ NS_IMETHODIMP nsChildView::Resize(double aWidth, double aHeight, bool aRepaint)
     [mView setFrame:DevPixelsToCocoaPoints(mBounds)];
   });
 
-  if (mVisible && aRepaint)
-    [mView setNeedsDisplay:YES];
+  if (mVisible && aRepaint) {
+    [[mView pixelHostingView] setNeedsDisplay:YES];
+  }
 
   NotifyRollupGeometryChange();
   ReportSizeEvent();
@@ -1021,8 +986,9 @@ NS_IMETHODIMP nsChildView::Resize(double aX, double aY,
     [mView setFrame:DevPixelsToCocoaPoints(mBounds)];
   });
 
-  if (mVisible && aRepaint)
-    [mView setNeedsDisplay:YES];
+  if (mVisible && aRepaint) {
+    [[mView pixelHostingView] setNeedsDisplay:YES];
+  }
 
   NotifyRollupGeometryChange();
   if (isMoving) {
@@ -1341,14 +1307,7 @@ NS_IMETHODIMP nsChildView::Invalidate(const LayoutDeviceIntRect& aRect)
   NS_ASSERTION(GetLayerManager()->GetBackendType() != LayersBackend::LAYERS_CLIENT,
                "Shouldn't need to invalidate with accelerated OMTC layers!");
 
-  if ([NSView focusView]) {
-    // if a view is focussed (i.e. being drawn), then postpone the invalidate so that we
-    // don't lose it.
-    [mView setNeedsPendingDisplayInRect:DevPixelsToCocoaPoints(aRect)];
-  }
-  else {
-    [mView setNeedsDisplayInRect:DevPixelsToCocoaPoints(aRect)];
-  }
+  [[mView pixelHostingView] setNeedsDisplayInRect:DevPixelsToCocoaPoints(aRect)];
 
   return NS_OK;
 
@@ -1920,13 +1879,6 @@ void
 nsChildView::ConfigureAPZCTreeManager()
 {
   nsBaseWidget::ConfigureAPZCTreeManager();
-
-  if (gfxPrefs::AsyncPanZoomSeparateEventThread()) {
-    if (gNumberOfWidgetsNeedingEventThread == 0) {
-      [EventThreadRunner start];
-    }
-    gNumberOfWidgetsNeedingEventThread++;
-  }
 }
 
 void
@@ -2557,14 +2509,6 @@ nsChildView::UpdateVibrancy(const nsTArray<ThemeGeometry>& aThemeGeometries)
   vm.UpdateVibrantRegion(VibrancyType::DARK, vibrantDarkRegion);
 }
 
-void
-nsChildView::ClearVibrantAreas()
-{
-  if (VibrancyManager::SystemSupportsVibrancy()) {
-    EnsureVibrancyManager().ClearVibrantAreas();
-  }
-}
-
 static VibrancyType
 ThemeGeometryTypeToVibrancyType(nsITheme::ThemeGeometryType aThemeGeometryType)
 {
@@ -2617,7 +2561,7 @@ nsChildView::EnsureVibrancyManager()
 {
   MOZ_ASSERT(mView, "Only call this once we have a view!");
   if (!mVibrancyManager) {
-    mVibrancyManager = MakeUnique<VibrancyManager>(*this, mView);
+    mVibrancyManager = MakeUnique<VibrancyManager>(*this, [mView vibrancyViewsContainer]);
   }
   return *mVibrancyManager;
 }
@@ -2787,9 +2731,10 @@ nsChildView::UpdateWindowDraggingRegion(const LayoutDeviceIntRegion& aRegion)
 
   // Suppress calls to setNeedsDisplay during NSView geometry changes.
   ManipulateViewWithoutNeedingDisplay(mView, ^() {
-    changed = mNonDraggableRegion.UpdateRegion(nonDraggable, *this, mView, ^() {
-      return [[NonDraggableView alloc] initWithFrame:NSZeroRect];
-    });
+    changed = mNonDraggableRegion.UpdateRegion(
+        nonDraggable, *this, [mView nonDraggableViewsContainer], ^() {
+          return [[NonDraggableView alloc] initWithFrame:NSZeroRect];
+        });
   });
 
   if (changed) {
@@ -3160,6 +3105,31 @@ private:
 
 #pragma mark -
 
+// ViewRegionContainerView is a view class for certain subviews of ChildView
+// which contain the NSViews created for ViewRegions (see ViewRegion.h).
+// It doesn't do anything interesting, it only acts as a container so that it's
+// easier for ChildView to control the z order of its children.
+@interface ViewRegionContainerView : NSView {
+}
+@end
+
+@implementation ViewRegionContainerView
+
+- (NSView*)hitTest:(NSPoint)aPoint {
+  return nil;  // Be transparent to mouse events.
+}
+
+- (BOOL)isFlipped {
+  return [[self superview] isFlipped];
+}
+
+- (BOOL)mouseDownCanMoveWindow {
+  return [[self superview] mouseDownCanMoveWindow];
+}
+
+@end
+;
+
 @implementation ChildView
 
 // globalDragPboard is non-null during native drag sessions that did not originate
@@ -3215,7 +3185,6 @@ NSEvent* gLastDragMouseDownEvent = nil;
 
   if ((self = [super initWithFrame:inFrame])) {
     mGeckoChild = inChild;
-    mPendingDisplay = NO;
     mBlockedLastMouseDown = NO;
     mExpectingWheelStop = NO;
 
@@ -3236,6 +3205,20 @@ NSEvent* gLastDragMouseDownEvent = nil;
     mCancelSwipeAnimation = nil;
 #endif
 
+    mNonDraggableViewsContainer = [[ViewRegionContainerView alloc] initWithFrame:[self bounds]];
+    mVibrancyViewsContainer = [[ViewRegionContainerView alloc] initWithFrame:[self bounds]];
+
+    [mNonDraggableViewsContainer setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
+    [mVibrancyViewsContainer setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
+
+    [self addSubview:mNonDraggableViewsContainer];
+    [self addSubview:mVibrancyViewsContainer];
+
+    mPixelHostingView = [[PixelHostingView alloc] initWithFrame:[self bounds]];
+    [mPixelHostingView setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
+
+    [self addSubview:mPixelHostingView];
+
     mTopLeftCornerMask = NULL;
   }
 
@@ -3250,10 +3233,9 @@ NSEvent* gLastDragMouseDownEvent = nil;
                                            selector:@selector(systemMetricsChanged)
                                                name:NSSystemColorsDidChangeNotification
                                              object:nil];
-  // TODO: replace the string with the constant once we build with the 10.7 SDK
   [[NSNotificationCenter defaultCenter] addObserver:self
                                            selector:@selector(scrollbarSystemMetricChanged)
-                                               name:@"NSPreferredScrollerStyleDidChangeNotification"
+                                               name:NSPreferredScrollerStyleDidChangeNotification
                                              object:nil];
   [[NSDistributedNotificationCenter defaultCenter] addObserver:self
                                                       selector:@selector(systemMetricsChanged)
@@ -3263,7 +3245,7 @@ NSEvent* gLastDragMouseDownEvent = nil;
   [[NSNotificationCenter defaultCenter] addObserver:self
                                            selector:@selector(_surfaceNeedsUpdate:)
                                                name:NSViewGlobalFrameDidChangeNotification
-                                             object:self];
+                                             object:mPixelHostingView];
 
   return self;
 
@@ -3348,12 +3330,23 @@ NSEvent* gLastDragMouseDownEvent = nil;
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
+- (NSView*)vibrancyViewsContainer {
+  return mVibrancyViewsContainer;
+}
+
+- (NSView*)nonDraggableViewsContainer {
+  return mNonDraggableViewsContainer;
+}
+
+- (NSView*)pixelHostingView {
+  return mPixelHostingView;
+}
+
 - (void)dealloc
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
   [mGLContext release];
-  [mPendingDirtyRects release];
   [mLastMouseDownEvent release];
   [mLastKeyDownEvent release];
   [mClickThroughMouseDownEvent release];
@@ -3362,6 +3355,12 @@ NSEvent* gLastDragMouseDownEvent = nil;
 
   [[NSNotificationCenter defaultCenter] removeObserver:self];
   [[NSDistributedNotificationCenter defaultCenter] removeObserver:self];
+  [mVibrancyViewsContainer removeFromSuperview];
+  [mVibrancyViewsContainer release];
+  [mNonDraggableViewsContainer removeFromSuperview];
+  [mNonDraggableViewsContainer release];
+  [mPixelHostingView removeFromSuperview];
+  [mPixelHostingView release];
 
   [super dealloc];
 
@@ -3408,82 +3407,6 @@ NSEvent* gLastDragMouseDownEvent = nil;
   }
 }
 
-- (void)setNeedsPendingDisplay
-{
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
-
-  mPendingFullDisplay = YES;
-  if (!mPendingDisplay) {
-    [self performSelector:@selector(processPendingRedraws) withObject:nil afterDelay:0];
-    mPendingDisplay = YES;
-  }
-
-  NS_OBJC_END_TRY_ABORT_BLOCK;
-}
-
-- (void)setNeedsPendingDisplayInRect:(NSRect)invalidRect
-{
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
-
-  if (!mPendingDirtyRects)
-    mPendingDirtyRects = [[NSMutableArray alloc] initWithCapacity:1];
-  [mPendingDirtyRects addObject:[NSValue valueWithRect:invalidRect]];
-  if (!mPendingDisplay) {
-    [self performSelector:@selector(processPendingRedraws) withObject:nil afterDelay:0];
-    mPendingDisplay = YES;
-  }
-
-  NS_OBJC_END_TRY_ABORT_BLOCK;
-}
-
-// Clears the queue of any pending invalides
-- (void)processPendingRedraws
-{
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
-
-  if (mPendingFullDisplay) {
-    [self setNeedsDisplay:YES];
-  }
-  else if (mPendingDirtyRects) {
-    unsigned int count = [mPendingDirtyRects count];
-    for (unsigned int i = 0; i < count; ++i) {
-      [self setNeedsDisplayInRect:[[mPendingDirtyRects objectAtIndex:i] rectValue]];
-    }
-  }
-  mPendingFullDisplay = NO;
-  mPendingDisplay = NO;
-  [mPendingDirtyRects release];
-  mPendingDirtyRects = nil;
-
-  NS_OBJC_END_TRY_ABORT_BLOCK;
-}
-
-- (void)setNeedsDisplayInRect:(NSRect)aRect
-{
-  if (![self isUsingOpenGL]) {
-    [super setNeedsDisplayInRect:aRect];
-    return;
-  }
-
-  if ([[self window] isVisible] && [self isUsingMainThreadOpenGL]) {
-    // Draw without calling drawRect. This prevent us from
-    // needing to access the normal window buffer surface unnecessarily, so we
-    // waste less time synchronizing the two surfaces. (These synchronizations
-    // show up in a profiler as CGSDeviceLock / _CGSLockWindow /
-    // _CGSSynchronizeWindowBackingStore.) It also means that Cocoa doesn't
-    // have any potentially expensive invalid rect management for us.
-    if (!mWaitingForPaint) {
-      mWaitingForPaint = YES;
-      // Use NSRunLoopCommonModes instead of the default NSDefaultRunLoopMode
-      // so that the timer also fires while a native menu is open.
-      [self performSelector:@selector(drawUsingOpenGLCallback)
-                 withObject:nil
-                 afterDelay:0
-                    inModes:[NSArray arrayWithObject:NSRunLoopCommonModes]];
-    }
-  }
-}
-
 - (NSString*)description
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;
@@ -3537,25 +3460,6 @@ NSEvent* gLastDragMouseDownEvent = nil;
   return YES;
 }
 
-- (void)scrollRect:(NSRect)aRect by:(NSSize)offset
-{
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
-
-  // Update any pending dirty rects to reflect the new scroll position
-  if (mPendingDirtyRects) {
-    unsigned int count = [mPendingDirtyRects count];
-    for (unsigned int i = 0; i < count; ++i) {
-      NSRect oldRect = [[mPendingDirtyRects objectAtIndex:i] rectValue];
-      NSRect newRect = NSOffsetRect(oldRect, offset.width, offset.height);
-      [mPendingDirtyRects replaceObjectAtIndex:i
-                                    withObject:[NSValue valueWithRect:newRect]];
-    }
-  }
-  [super scrollRect:aRect by:offset];
-
-  NS_OBJC_END_TRY_ABORT_BLOCK;
-}
-
 - (BOOL)mouseDownCanMoveWindow
 {
   // Return YES so that parts of this view can be draggable. The non-draggable
@@ -3567,7 +3471,7 @@ NSEvent* gLastDragMouseDownEvent = nil;
 
 -(void)updateGLContext
 {
-  [mGLContext setView:self];
+  [mGLContext setView:mPixelHostingView];
   [mGLContext update];
 }
 
@@ -3580,11 +3484,6 @@ NSEvent* gLastDragMouseDownEvent = nil;
   }
 }
 
-- (BOOL)wantsBestResolutionOpenGLSurface
-{
-  return nsCocoaUtils::HiDPIEnabled() ? YES : NO;
-}
-
 - (void)viewDidChangeBackingProperties
 {
   [super viewDidChangeBackingProperties];
@@ -3646,7 +3545,7 @@ NSEvent* gLastDragMouseDownEvent = nil;
   LayoutDeviceIntRect boundingRect = mGeckoChild->CocoaPointsToDevPixels(aRect);
   const NSRect *rects;
   NSInteger count;
-  [self getRectsBeingDrawn:&rects count:&count];
+  [mPixelHostingView getRectsBeingDrawn:&rects count:&count];
 
   if (count > MAX_RECTS_IN_REGION) {
     return boundingRect;
@@ -3662,53 +3561,34 @@ NSEvent* gLastDragMouseDownEvent = nil;
 
 // The display system has told us that a portion of our view is dirty. Tell
 // gecko to paint it
-- (void)drawRect:(NSRect)aRect
+// This method is called from mPixelHostingView's drawRect handler.
+- (void)doDrawRect:(NSRect)aRect
 {
-  CGContextRef cgContext = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
-  [self drawRect:aRect inContext:cgContext];
-
-  // If we're a transparent window and our contents have changed, we need
-  // to make sure the shadow is updated to the new contents.
-  if ([[self window] isKindOfClass:[BaseWindow class]]) {
-    [(BaseWindow*)[self window] deferredInvalidateShadow];
+  if (!NS_IsMainThread()) {
+    // In the presence of CoreAnimation, this method can sometimes be called on
+    // a non-main thread. Ignore those calls because Gecko can only react to
+    // them on the main thread.
+    return;
   }
-}
 
-- (void)drawRect:(NSRect)aRect inContext:(CGContextRef)aContext
-{
   if (!mGeckoChild || !mGeckoChild->IsVisible())
     return;
-
-#ifdef DEBUG_UPDATE
-  LayoutDeviceIntRect geckoBounds = mGeckoChild->GetBounds();
-
-  fprintf (stderr, "---- Update[%p][%p] [%f %f %f %f] cgc: %p\n  gecko bounds: [%d %d %d %d]\n",
-           self, mGeckoChild,
-           aRect.origin.x, aRect.origin.y, aRect.size.width, aRect.size.height, aContext,
-           geckoBounds.x, geckoBounds.y, geckoBounds.width, geckoBounds.height);
-
-  CGAffineTransform xform = CGContextGetCTM(aContext);
-  fprintf (stderr, "  xform in: [%f %f %f %f %f %f]\n", xform.a, xform.b, xform.c, xform.d, xform.tx, xform.ty);
-#endif
+  CGContextRef cgContext = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
 
   if ([self isUsingOpenGL]) {
-    // For Gecko-initiated repaints in OpenGL mode, drawUsingOpenGL is
-    // directly called from a delayed perform callback - without going through
-    // drawRect.
-    // Paints that come through here are triggered by something that Cocoa
-    // controls, for example by window resizing or window focus changes.
-
     // Since this view is usually declared as opaque, the window's pixel
     // buffer may now contain garbage which we need to prevent from reaching
     // the screen. The only place where garbage can show is in the window
     // corners and the vibrant regions of the window - the rest of the window
     // is covered by opaque content in our OpenGL surface.
     // So we need to clear the pixel buffer contents in these areas.
-    mGeckoChild->ClearVibrantAreas();
     [self clearCorners];
 
-    // Do GL composition and return.
-    [self drawUsingOpenGL];
+    // Force a sync OMTC composite into the OpenGL context and return.
+    LayoutDeviceIntRect geckoBounds = mGeckoChild->GetBounds();
+    LayoutDeviceIntRegion region(geckoBounds);
+
+    mGeckoChild->PaintWindow(region);
     return;
   }
 
@@ -3720,54 +3600,31 @@ NSEvent* gLastDragMouseDownEvent = nil;
   // multiple dev pixels. But Gecko expects its supplied context to be scaled
   // to device pixels, so we need to reverse the scaling.
   double scale = mGeckoChild->BackingScaleFactor();
-  CGContextSaveGState(aContext);
-  CGContextScaleCTM(aContext, 1.0 / scale, 1.0 / scale);
+  CGContextSaveGState(cgContext);
+  CGContextScaleCTM(cgContext, 1.0 / scale, 1.0 / scale);
 
   NSSize viewSize = [self bounds].size;
   gfx::IntSize backingSize = gfx::IntSize::Truncate(viewSize.width * scale, viewSize.height * scale);
   LayoutDeviceIntRegion region = [self nativeDirtyRegionWithBoundingRect:aRect];
 
-  bool painted = mGeckoChild->PaintWindowInContext(aContext, region, backingSize);
+  bool painted = mGeckoChild->PaintWindowInContext(cgContext, region, backingSize);
 
   // Undo the scale transform so that from now on the context is in
   // CocoaPoints again.
-  CGContextRestoreGState(aContext);
+  CGContextRestoreGState(cgContext);
 
-  if (!painted && [self isOpaque]) {
+  if (!painted && [mPixelHostingView isOpaque]) {
     // Gecko refused to draw, but we've claimed to be opaque, so we have to
     // draw something--fill with white.
-    CGContextSetRGBFillColor(aContext, 1, 1, 1, 1);
-    CGContextFillRect(aContext, NSRectToCGRect(aRect));
+    CGContextSetRGBFillColor(cgContext, 1, 1, 1, 1);
+    CGContextFillRect(cgContext, NSRectToCGRect(aRect));
   }
 
   if ([self isCoveringTitlebar]) {
     [self drawTitleString];
     [self drawTitlebarHighlight];
-    [self maskTopCornersInContext:aContext];
+    [self maskTopCornersInContext:cgContext];
   }
-
-#ifdef DEBUG_UPDATE
-  fprintf (stderr, "---- update done ----\n");
-
-#if 0
-  CGContextSetRGBStrokeColor (aContext,
-                            ((((unsigned long)self) & 0xff)) / 255.0,
-                            ((((unsigned long)self) & 0xff00) >> 8) / 255.0,
-                            ((((unsigned long)self) & 0xff0000) >> 16) / 255.0,
-                            0.5);
-#endif
-  CGContextSetRGBStrokeColor(aContext, 1, 0, 0, 0.8);
-  CGContextSetLineWidth(aContext, 4.0);
-  CGContextStrokeRect(aContext, NSRectToCGRect(aRect));
-#endif
-}
-
-- (BOOL)isUsingMainThreadOpenGL
-{
-  if (!mGeckoChild || ![self window])
-    return NO;
-
-  return mGeckoChild->GetLayerManager(nullptr)->GetBackendType() == mozilla::layers::LayersBackend::LAYERS_OPENGL;
 }
 
 - (BOOL)isUsingOpenGL
@@ -3775,33 +3632,9 @@ NSEvent* gLastDragMouseDownEvent = nil;
   if (!mGeckoChild || ![self window])
     return NO;
 
-  return mGLContext || mUsingOMTCompositor || [self isUsingMainThreadOpenGL];
-}
-
-- (void)drawUsingOpenGL
-{
-  PROFILER_LABEL("ChildView", "drawUsingOpenGL",
-    js::ProfileEntry::Category::GRAPHICS);
-
-  if (![self isUsingOpenGL] || !mGeckoChild->IsVisible())
-    return;
-
-  mWaitingForPaint = NO;
-
-  LayoutDeviceIntRect geckoBounds = mGeckoChild->GetBounds();
-  LayoutDeviceIntRegion region(geckoBounds);
-
-  mGeckoChild->PaintWindow(region);
+  return mGLContext || mUsingOMTCompositor;
 }
 
-// Called asynchronously after setNeedsDisplay in order to avoid entering the
-// normal drawing machinery.
-- (void)drawUsingOpenGLCallback
-{
-  if (mWaitingForPaint) {
-    [self drawUsingOpenGL];
-  }
-}
 
 - (BOOL)hasRoundedBottomCorners
 {
@@ -4803,12 +4636,6 @@ GetIntegerDeltaForEvent(NSEvent* aEvent)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
-  if (gfxPrefs::AsyncPanZoomSeparateEventThread() && [self apzctm]) {
-    // Disable main-thread scrolling completely when using APZ with the
-    // separate event thread. This is bug 1013412.
-    return;
-  }
-
   nsAutoRetainCocoaObject kungFuDeathGrip(self);
 
   ChildViewMouseTracker::MouseScrolled(theEvent);
@@ -4928,105 +4755,6 @@ GetIntegerDeltaForEvent(NSEvent* aEvent)
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
-- (void)handleAsyncScrollEvent:(CGEventRef)cgEvent ofType:(CGEventType)type
-{
-  IAPZCTreeManager* apzctm = [self apzctm];
-  if (!apzctm) {
-    return;
-  }
-
-  CGPoint loc = CGEventGetLocation(cgEvent);
-  loc.y = nsCocoaUtils::FlippedScreenY(loc.y);
-  NSPoint locationInWindow =
-    nsCocoaUtils::ConvertPointFromScreen([self window], NSPointFromCGPoint(loc));
-  ScreenIntPoint location = ViewAs<ScreenPixel>(
-    [self convertWindowCoordinates:locationInWindow],
-    PixelCastJustification::LayoutDeviceIsScreenForUntransformedEvent);
-
-  static NSTimeInterval sStartTime = [NSDate timeIntervalSinceReferenceDate];
-  static TimeStamp sStartTimeStamp = TimeStamp::Now();
-
-  if (type == kCGEventScrollWheel) {
-    NSEvent* event = [NSEvent eventWithCGEvent:cgEvent];
-    NSEventPhase phase = nsCocoaUtils::EventPhase(event);
-    NSEventPhase momentumPhase = nsCocoaUtils::EventMomentumPhase(event);
-    CGFloat pixelDeltaX = 0, pixelDeltaY = 0;
-    nsCocoaUtils::GetScrollingDeltas(event, &pixelDeltaX, &pixelDeltaY);
-    uint32_t eventTime = ([event timestamp] - sStartTime) * 1000;
-    TimeStamp eventTimeStamp = sStartTimeStamp +
-      TimeDuration::FromSeconds([event timestamp] - sStartTime);
-    NSPoint locationInWindowMoved = NSMakePoint(
-      locationInWindow.x + pixelDeltaX,
-      locationInWindow.y - pixelDeltaY);
-    ScreenIntPoint locationMoved = ViewAs<ScreenPixel>(
-      [self convertWindowCoordinates:locationInWindowMoved],
-      PixelCastJustification::LayoutDeviceIsScreenForUntransformedEvent);
-    ScreenPoint delta = ScreenPoint(locationMoved - location);
-    ScrollableLayerGuid guid;
-
-    // MayBegin and Cancelled are dispatched when the fingers start or stop
-    // touching the touchpad before any scrolling has occurred. These events
-    // can be used to control scrollbar visibility or interrupt scroll
-    // animations. They are only dispatched on 10.8 or later, and only by
-    // relatively modern devices.
-    if (phase == NSEventPhaseMayBegin) {
-      PanGestureInput panInput(PanGestureInput::PANGESTURE_MAYSTART, eventTime,
-                               eventTimeStamp, location, ScreenPoint(0, 0), 0);
-      apzctm->ReceiveInputEvent(panInput, &guid, nullptr);
-      return;
-    }
-    if (phase == NSEventPhaseCancelled) {
-      PanGestureInput panInput(PanGestureInput::PANGESTURE_CANCELLED, eventTime,
-                               eventTimeStamp, location, ScreenPoint(0, 0), 0);
-      apzctm->ReceiveInputEvent(panInput, &guid, nullptr);
-      return;
-    }
-
-    // Legacy scroll events are dispatched by devices that do not have a
-    // concept of a scroll gesture, for example by USB mice with
-    // traditional mouse wheels.
-    // For these kinds of scrolls, we want to surround every single scroll
-    // event with a PANGESTURE_START and a PANGESTURE_END event. The APZC
-    // needs to know that the real scroll gesture can end abruptly after any
-    // one of these events.
-    bool isLegacyScroll = (phase == NSEventPhaseNone &&
-      momentumPhase == NSEventPhaseNone && delta != ScreenPoint(0, 0));
-
-    if (phase == NSEventPhaseBegan || isLegacyScroll) {
-      PanGestureInput panInput(PanGestureInput::PANGESTURE_START, eventTime,
-                               eventTimeStamp, location, ScreenPoint(0, 0), 0);
-      apzctm->ReceiveInputEvent(panInput, &guid, nullptr);
-    }
-    if (momentumPhase == NSEventPhaseNone && delta != ScreenPoint(0, 0)) {
-      PanGestureInput panInput(PanGestureInput::PANGESTURE_PAN, eventTime,
-                               eventTimeStamp, location, delta, 0);
-      apzctm->ReceiveInputEvent(panInput, &guid, nullptr);
-    }
-    if (phase == NSEventPhaseEnded || isLegacyScroll) {
-      PanGestureInput panInput(PanGestureInput::PANGESTURE_END, eventTime,
-                               eventTimeStamp, location, ScreenPoint(0, 0), 0);
-      apzctm->ReceiveInputEvent(panInput, &guid, nullptr);
-    }
-
-    // Any device that can dispatch momentum events supports all three momentum phases.
-    if (momentumPhase == NSEventPhaseBegan) {
-      PanGestureInput panInput(PanGestureInput::PANGESTURE_MOMENTUMSTART, eventTime,
-                               eventTimeStamp, location, ScreenPoint(0, 0), 0);
-      apzctm->ReceiveInputEvent(panInput, &guid, nullptr);
-    }
-    if (momentumPhase == NSEventPhaseChanged && delta != ScreenPoint(0, 0)) {
-      PanGestureInput panInput(PanGestureInput::PANGESTURE_MOMENTUMPAN, eventTime,
-                               eventTimeStamp, location, delta, 0);
-      apzctm->ReceiveInputEvent(panInput, &guid, nullptr);
-    }
-    if (momentumPhase == NSEventPhaseEnded) {
-      PanGestureInput panInput(PanGestureInput::PANGESTURE_MOMENTUMEND, eventTime,
-                               eventTimeStamp, location, ScreenPoint(0, 0), 0);
-      apzctm->ReceiveInputEvent(panInput, &guid, nullptr);
-    }
-  }
-}
-
 -(NSMenu*)menuForEvent:(NSEvent*)theEvent
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;
@@ -5571,11 +5299,6 @@ GetIntegerDeltaForEvent(NSEvent* aEvent)
   return mGeckoChild->CocoaPointsToDevPixelsRoundDown(localPoint);
 }
 
-- (IAPZCTreeManager*)apzctm
-{
-  return mGeckoChild ? mGeckoChild->APZCTM() : nullptr;
-}
-
 // This is a utility function used by NSView drag event methods
 // to send events. It contains all of the logic needed for Gecko
 // dragging to work. Returns the appropriate cocoa drag operation code.
@@ -6209,6 +5932,26 @@ nsChildView::GetSelectionAsPlaintext(nsAString& aResult)
 
 @end
 
+@implementation PixelHostingView
+
+- (BOOL)isFlipped {
+  return YES;
+}
+
+- (NSView*)hitTest:(NSPoint)aPoint {
+  return nil;
+}
+
+- (void)drawRect:(NSRect)aRect {
+  [(ChildView*)[self superview] doDrawRect:aRect];
+}
+
+- (BOOL)wantsBestResolutionOpenGLSurface {
+  return nsCocoaUtils::HiDPIEnabled() ? YES : NO;
+}
+
+@end
+
 #pragma mark -
 
 void
@@ -6377,106 +6120,6 @@ ChildViewMouseTracker::WindowAcceptsEvent(NSWindow* aWindow, NSEvent* aEvent,
 
 #pragma mark -
 
-@interface EventThreadRunner(Private)
-- (void)runEventThread;
-- (void)shutdownAndReleaseCalledOnEventThread;
-- (void)shutdownAndReleaseCalledOnAnyThread;
-- (void)handleEvent:(CGEventRef)cgEvent type:(CGEventType)type;
-@end
-
-static EventThreadRunner* sEventThreadRunner = nil;
-
-@implementation EventThreadRunner
-
-+ (void)start
-{
-  sEventThreadRunner = [[EventThreadRunner alloc] init];
-}
-
-+ (void)stop
-{
-  if (sEventThreadRunner) {
-    [sEventThreadRunner shutdownAndReleaseCalledOnAnyThread];
-    sEventThreadRunner = nil;
-  }
-}
-
-- (id)init
-{
-  if ((self = [super init])) {
-    mThread = nil;
-    [NSThread detachNewThreadSelector:@selector(runEventThread)
-                             toTarget:self
-                           withObject:nil];
-  }
-  return self;
-}
-
-static CGEventRef
-HandleEvent(CGEventTapProxy aProxy, CGEventType aType,
-            CGEventRef aEvent, void* aClosure)
-{
-  [(EventThreadRunner*)aClosure handleEvent:aEvent type:aType];
-  return aEvent;
-}
-
-- (void)runEventThread
-{
-  char aLocal;
-  profiler_register_thread("APZC Event Thread", &aLocal);
-  PR_SetCurrentThreadName("APZC Event Thread");
-
-  mThread = [NSThread currentThread];
-  ProcessSerialNumber currentProcess;
-  GetCurrentProcess(&currentProcess);
-  CFMachPortRef eventPort =
-    CGEventTapCreateForPSN(&currentProcess,
-                           kCGHeadInsertEventTap,
-                           kCGEventTapOptionListenOnly,
-                           CGEventMaskBit(kCGEventScrollWheel),
-                           HandleEvent,
-                           self);
-  CFRunLoopSourceRef eventPortSource =
-    CFMachPortCreateRunLoopSource(kCFAllocatorSystemDefault, eventPort, 0);
-  CFRunLoopAddSource(CFRunLoopGetCurrent(), eventPortSource, kCFRunLoopCommonModes);
-  CFRunLoopRun();
-  CFRunLoopRemoveSource(CFRunLoopGetCurrent(), eventPortSource, kCFRunLoopCommonModes);
-  CFRelease(eventPortSource);
-  CFRelease(eventPort);
-  [self release];
-}
-
-- (void)shutdownAndReleaseCalledOnEventThread
-{
-  CFRunLoopStop(CFRunLoopGetCurrent());
-}
-
-- (void)shutdownAndReleaseCalledOnAnyThread
-{
-  [self performSelector:@selector(shutdownAndReleaseCalledOnEventThread) onThread:mThread withObject:nil waitUntilDone:NO];
-}
-
-static const CGEventField kCGWindowNumberField = (const CGEventField) 51;
-
-// Called on scroll thread
-- (void)handleEvent:(CGEventRef)cgEvent type:(CGEventType)type
-{
-  if (type != kCGEventScrollWheel) {
-    return;
-  }
-
-  int windowNumber = CGEventGetIntegerValueField(cgEvent, kCGWindowNumberField);
-  NSWindow* window = [NSApp windowWithWindowNumber:windowNumber];
-  if (!window || ![window isKindOfClass:[BaseWindow class]]) {
-    return;
-  }
-
-  ChildView* childView = [(BaseWindow*)window mainChildView];
-  [childView handleAsyncScrollEvent:cgEvent ofType:type];
-}
-
-@end
-
 @interface NSView (MethodSwizzling)
 - (BOOL)nsChildView_NSView_mouseDownCanMoveWindow;
 @end
diff --git a/widget/cocoa/nsCocoaFeatures.h b/widget/cocoa/nsCocoaFeatures.h
index 984dae80e1..7ebbe759fd 100644
--- a/widget/cocoa/nsCocoaFeatures.h
+++ b/widget/cocoa/nsCocoaFeatures.h
@@ -24,6 +24,7 @@ public:
   static bool OnHighSierraOrLater();
   static bool OnMojaveOrLater();
   static bool OnCatalinaOrLater();
+  static bool OnBigSurOrLater();
 
   static bool IsAtLeastVersion(int32_t aMajor, int32_t aMinor, int32_t aBugFix=0);
 
diff --git a/widget/cocoa/nsCocoaFeatures.mm b/widget/cocoa/nsCocoaFeatures.mm
index 065260837c..0b22c51bd1 100644
--- a/widget/cocoa/nsCocoaFeatures.mm
+++ b/widget/cocoa/nsCocoaFeatures.mm
@@ -22,6 +22,8 @@
 #define MAC_OS_X_VERSION_10_13_HEX 0x000010D0
 #define MAC_OS_X_VERSION_10_14_HEX 0x000010E0
 #define MAC_OS_X_VERSION_10_15_HEX 0x000010F0
+#define MAC_OS_X_VERSION_10_16_HEX 0x000A1000
+#define MAC_OS_X_VERSION_11_0_HEX  0x000B0000
 
 #include "nsCocoaFeatures.h"
 #include "nsCocoaUtils.h"
@@ -189,6 +191,14 @@ nsCocoaFeatures::OnCatalinaOrLater()
 }
 
 /* static */ bool
+nsCocoaFeatures::OnBigSurOrLater() {
+  // Account for the version being 10.16 (which occurs when the
+  // application is linked with an older SDK) or 11.0 on Big Sur.
+  return ((OSXVersion() >= MAC_OS_X_VERSION_10_16_HEX) ||
+          (OSXVersion() >= MAC_OS_X_VERSION_11_0_HEX));
+}
+
+/* static */ bool
 nsCocoaFeatures::IsAtLeastVersion(int32_t aMajor, int32_t aMinor, int32_t aBugFix)
 {
     return OSXVersion() >= GetVersion(aMajor, aMinor, aBugFix);
diff --git a/widget/cocoa/nsCocoaWindow.h b/widget/cocoa/nsCocoaWindow.h
index 6338f474df..1913696b8c 100644
--- a/widget/cocoa/nsCocoaWindow.h
+++ b/widget/cocoa/nsCocoaWindow.h
@@ -359,7 +359,8 @@ protected:
   nsresult             CreateNativeWindow(const NSRect &aRect,
                                           nsBorderStyle aBorderStyle,
                                           bool aRectIsFrameRect);
-  nsresult             CreatePopupContentView(const LayoutDeviceIntRect &aRect);
+  nsresult             CreatePopupContentView(const LayoutDeviceIntRect &aRect,
+                                              nsWidgetInitData* aInitData);
   void                 DestroyNativeWindow();
   void                 AdjustWindowShadow();
   void                 SetWindowBackgroundBlur();
@@ -416,6 +417,8 @@ protected:
   bool                 mInReportMoveEvent; // true if in a call to ReportMoveEvent().
   bool                 mInResize; // true if in a call to DoResize().
 
+  bool                 mAlwaysOnTop;
+
   int32_t              mNumModalDescendents;
   InputContext         mInputContext;
 };
diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
index 4e7d11b78d..a437504fd1 100644
--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -34,6 +34,7 @@
 #include "nsIWidgetListener.h"
 #include "nsIPresShell.h"
 #include "nsScreenCocoa.h"
+#include "VibrancyManager.h"
 
 #include "gfxPlatform.h"
 #include "qcms.h"
@@ -127,6 +128,7 @@ nsCocoaWindow::nsCocoaWindow()
 , mIsAnimationSuppressed(false)
 , mInReportMoveEvent(false)
 , mInResize(false)
+, mAlwaysOnTop(false)
 , mNumModalDescendents(0)
 {
   if ([NSWindow respondsToSelector:@selector(setAllowsAutomaticWindowTabbing:)]) {
@@ -301,12 +303,14 @@ nsCocoaWindow::Create(nsIWidget* aParent,
   if (mWindowType == eWindowType_popup) {
     if (aInitData->mMouseTransparent) {
       [mWindow setIgnoresMouseEvents:YES];
+    } else {
+      [mWindow setIgnoresMouseEvents:NO];
     }
     // now we can convert newBounds to device pixels for the window we created,
     // as the child view expects a rect expressed in the dev pix of its parent
     LayoutDeviceIntRect devRect =
       RoundedToInt(newBounds * GetDesktopToDeviceScale());
-    return CreatePopupContentView(devRect);
+    return CreatePopupContentView(devRect, aInitData);
   }
 
   mIsAnimationSuppressed = aInitData->mIsAnimationSuppressed;
@@ -455,6 +459,11 @@ nsresult nsCocoaWindow::CreateNativeWindow(const NSRect &aRect,
   mWindow = [[windowClass alloc] initWithContentRect:contentRect styleMask:features 
                                  backing:NSBackingStoreBuffered defer:YES];
 
+  // Make sure that window titles don't leak to disk in private browsing mode
+  // due to macOS' resume feature.
+  [mWindow setRestorable:NO];
+  [mWindow disableSnapshotRestoration];
+
   // setup our notification delegate. Note that setDelegate: does NOT retain.
   mDelegate = [[WindowDelegate alloc] initWithGeckoWindow:this];
   [mWindow setDelegate:mDelegate];
@@ -473,7 +482,6 @@ nsresult nsCocoaWindow::CreateNativeWindow(const NSRect &aRect,
 
   if (mWindowType == eWindowType_popup) {
     SetPopupWindowLevel();
-    [mWindow setHasShadow:YES];
     [mWindow setBackgroundColor:[NSColor clearColor]];
     [mWindow setOpaque:NO];
   } else {
@@ -482,6 +490,13 @@ nsresult nsCocoaWindow::CreateNativeWindow(const NSRect &aRect,
     [mWindow setOpaque:YES];
   }
 
+  NSWindowCollectionBehavior newBehavior = [mWindow collectionBehavior];
+  if (mAlwaysOnTop) {
+    [mWindow setLevel:NSFloatingWindowLevel];
+    newBehavior |= NSWindowCollectionBehaviorCanJoinAllSpaces;
+  }
+  [mWindow setCollectionBehavior:newBehavior];
+
   [mWindow setContentMinSize:NSMakeSize(60, 60)];
   [mWindow disableCursorRects];
 
@@ -498,7 +513,8 @@ nsresult nsCocoaWindow::CreateNativeWindow(const NSRect &aRect,
 }
 
 NS_IMETHODIMP
-nsCocoaWindow::CreatePopupContentView(const LayoutDeviceIntRect &aRect)
+nsCocoaWindow::CreatePopupContentView(const LayoutDeviceIntRect &aRect,
+	                                  nsWidgetInitData* aInitData)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
 
@@ -511,13 +527,16 @@ nsCocoaWindow::CreatePopupContentView(const LayoutDeviceIntRect &aRect)
 
   nsIWidget* thisAsWidget = static_cast<nsIWidget*>(this);
   nsresult rv = mPopupContentView->Create(thisAsWidget, nullptr, aRect,
-                                          nullptr);
+                                          aInitData);
   if (NS_WARN_IF(NS_FAILED(rv))) {
     return rv;
   }
 
-  ChildView* newContentView = (ChildView*)mPopupContentView->GetNativeData(NS_NATIVE_WIDGET);
-  [mWindow setContentView:newContentView];
+  NSView* contentView = [mWindow contentView];
+  ChildView* childView = (ChildView*)mPopupContentView->GetNativeData(NS_NATIVE_WIDGET);
+  [childView setFrame:NSZeroRect];
+  [childView setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
+  [contentView addSubview:childView];
 
   return NS_OK;
 
@@ -756,6 +775,13 @@ NS_IMETHODIMP nsCocoaWindow::Show(bool bState)
     (NSWindow*)parentWidget->GetNativeData(NS_NATIVE_WINDOW) : nil;
 
   if (bState && !mBounds.IsEmpty()) {
+    // Don't try to show a popup when the parent isn't visible or is minimized.
+    if (mWindowType == eWindowType_popup && nativeParentWindow) {
+      if (![nativeParentWindow isVisible] || [nativeParentWindow isMiniaturized]) {
+        return NS_ERROR_FAILURE;
+      }
+    }
+
     if (mPopupContentView) {
       // Ensure our content view is visible. We never need to hide it.
       mPopupContentView->Show(true);
@@ -2789,12 +2815,6 @@ static NSMutableSet *gSwizzledFrameViewClasses = nil;
  - (void)_addKnownSubview:(NSView*)aView positioned:(NSWindowOrderingMode)place relativeTo:(NSView*)otherView;
 @end
 
-// Available on 10.10
-@interface NSWindow(PrivateCornerMaskMethod)
- - (id)_cornerMask;
- - (void)_cornerMaskChanged;
-@end
-
 #if !defined(MAC_OS_X_VERSION_10_10) || \
     MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_10
 
@@ -2815,6 +2835,10 @@ static NSMutableSet *gSwizzledFrameViewClasses = nil;
 
 #endif
 
+@interface NSView(NSVisualEffectViewSetMaskImage)
+- (void)setMaskImage:(NSImage*)image;
+@end
+
 @interface BaseWindow(Private)
 - (void)removeTrackingArea;
 - (void)cursorUpdated:(NSEvent*)aEvent;
@@ -2824,25 +2848,6 @@ static NSMutableSet *gSwizzledFrameViewClasses = nil;
 
 @implementation BaseWindow
 
-- (id)_cornerMask
-{
-  if (!mUseMenuStyle) {
-    return [super _cornerMask];
-  }
-
-  CGFloat radius = 4.0f;
-  NSEdgeInsets insets = { 5, 5, 5, 5 };
-  NSSize maskSize = { 12, 12 };
-  NSImage* maskImage = [NSImage imageWithSize:maskSize flipped:YES drawingHandler:^BOOL(NSRect dstRect) {
-    NSBezierPath *path = [NSBezierPath bezierPathWithRoundedRect:dstRect xRadius:radius yRadius:radius];
-    [[NSColor colorWithDeviceWhite:1.0 alpha:1.0] set];
-    [path fill];
-    return YES;
-  }];
-  [maskImage setCapInsets:insets];
-  return maskImage;
-}
-
 // The frame of a window is implemented using undocumented NSView subclasses.
 // We offset the window buttons by overriding the methods _closeButtonOrigin
 // and _fullScreenButtonOrigin on these frame view classes. The class which is
@@ -2915,14 +2920,54 @@ static NSMutableSet *gSwizzledFrameViewClasses = nil;
   return self;
 }
 
+// Returns an autoreleased NSImage.
+static NSImage*
+GetMenuMaskImage()
+{
+  CGFloat radius = 4.0f;
+  NSEdgeInsets insets = { 5, 5, 5, 5 };
+  NSSize maskSize = { 12, 12 };
+  NSImage* maskImage = [NSImage imageWithSize:maskSize flipped:YES drawingHandler:^BOOL(NSRect dstRect) {
+    NSBezierPath *path = [NSBezierPath bezierPathWithRoundedRect:dstRect xRadius:radius yRadius:radius];
+    [[NSColor colorWithDeviceWhite:1.0 alpha:1.0] set];
+    [path fill];
+    return YES;
+  }];
+  [maskImage setCapInsets:insets];
+  return maskImage;
+}
+
+- (void)swapOutChildViewWrapper:(NSView*)aNewWrapper
+{
+  [aNewWrapper setFrame:[[self contentView] frame]];
+  NSView* childView = [[self mainChildView] retain];
+  [childView removeFromSuperview];
+  [aNewWrapper addSubview:childView];
+  [childView release];
+  [super setContentView:aNewWrapper];
+}
+
 - (void)setUseMenuStyle:(BOOL)aValue
 {
-  if (aValue != mUseMenuStyle) {
-    mUseMenuStyle = aValue;
-    if ([self respondsToSelector:@selector(_cornerMaskChanged)]) {
-      [self _cornerMaskChanged];
+  if (!VibrancyManager::SystemSupportsVibrancy()) {
+    return;
+  }
+
+  if (aValue && !mUseMenuStyle) {
+    // Turn on rounded corner masking.
+    NSView* effectView = VibrancyManager::CreateEffectView(VibrancyType::MENU, YES);
+    if ([effectView respondsToSelector:@selector(setMaskImage:)]) {
+      [effectView setMaskImage:GetMenuMaskImage()];
     }
+    [self swapOutChildViewWrapper:effectView];
+    [effectView release];
+  } else if (mUseMenuStyle && !aValue) {
+    // Turn off rounded corner masking.
+    NSView* wrapper = [[NSView alloc] initWithFrame:NSZeroRect];
+    [self swapOutChildViewWrapper:wrapper];
+    [wrapper release];
   }
+  mUseMenuStyle = aValue;
 }
 
 - (void)setBeingShown:(BOOL)aValue
@@ -3080,10 +3125,6 @@ static const NSString* kStateCollectionBehavior = @"collectionBehavior";
 - (ChildView*)mainChildView
 {
   NSView *contentView = [self contentView];
-  // A PopupWindow's contentView is a ChildView object.
-  if ([contentView isKindOfClass:[ChildView class]]) {
-    return (ChildView*)contentView;
-  }
   NSView* lastView = [[contentView subviews] lastObject];
   if ([lastView isKindOfClass:[ChildView class]]) {
     return (ChildView*)lastView;
diff --git a/widget/cocoa/nsNativeThemeCocoa.mm b/widget/cocoa/nsNativeThemeCocoa.mm
index fc4f7f2e93..f93e40f7b5 100644
--- a/widget/cocoa/nsNativeThemeCocoa.mm
+++ b/widget/cocoa/nsNativeThemeCocoa.mm
@@ -443,8 +443,8 @@ static ChildView* ChildViewForFrame(nsIFrame* aFrame)
   if (!widget)
     return nil;
 
-  NSView* view = (NSView*)widget->GetNativeData(NS_NATIVE_WIDGET);
-  return [view isKindOfClass:[ChildView class]] ? (ChildView*)view : nil;
+  NSWindow* window = (NSWindow*)widget->GetNativeData(NS_NATIVE_WINDOW);
+  return [window isKindOfClass:[BaseWindow class]] ? [(BaseWindow*)window mainChildView]  : nil;
 }
 
 static NSWindow* NativeWindowForFrame(nsIFrame* aFrame,
@@ -2437,17 +2437,30 @@ nsNativeThemeCocoa::DrawWidgetBackground(nsRenderingContext* aContext,
       break;
 
     case NS_THEME_MENUSEPARATOR: {
-      ThemeMenuState menuState;
-      if (IsDisabled(aFrame, eventState)) {
-        menuState = kThemeMenuDisabled;
+      // Workaround for visual artifacts issues with
+      // HIThemeDrawMenuSeparator on macOS Big Sur.
+      if (nsCocoaFeatures::OnBigSurOrLater()) {
+        CGRect separatorRect = macRect;
+        separatorRect.size.height = 1;
+        separatorRect.size.width -= 42;
+        separatorRect.origin.x += 21;
+        // Use a gray color similar to the native separator
+        CGContextSetRGBFillColor(cgContext, 0.816, 0.816, 0.816, 1.0);
+        CGContextFillRect(cgContext, separatorRect);
       }
-      else {
-        menuState = CheckBooleanAttr(aFrame, nsGkAtoms::menuactive) ?
-                    kThemeMenuSelected : kThemeMenuActive;
+      else
+      {
+        ThemeMenuState menuState;
+        if (IsDisabled(aFrame, eventState)) {
+           menuState = kThemeMenuDisabled;
+        }
+        else {
+          menuState = CheckBooleanAttr(aFrame, nsGkAtoms::menuactive) ?
+                      kThemeMenuSelected : kThemeMenuActive;
+        }
+        HIThemeMenuItemDrawInfo midi = { 0, kThemeMenuItemPlain, menuState };
+        HIThemeDrawMenuSeparator(&macRect, &macRect, &midi, cgContext, HITHEME_ORIENTATION);
       }
-
-      HIThemeMenuItemDrawInfo midi = { 0, kThemeMenuItemPlain, menuState };
-      HIThemeDrawMenuSeparator(&macRect, &macRect, &midi, cgContext, HITHEME_ORIENTATION);
     }
       break;