Bug 1255555 - When a frame reconstruction triggers caret elements to be cloned, ensure the dummy touch listeners are re-registered on the clones. r=tylin

MozReview-Commit-ID: 8txWmd64LC9

layout/base/AccessibleCaret.cpp

@@ -187,6 +187,18 @@ AccessibleCaret::Contains(const nsPoint& aPoint) const
   return rect.Contains(aPoint);
 }
 
+void
+AccessibleCaret::EnsureApzAware()
+{
+  // If the caret element was cloned, the listener might have been lost. So
+  // if that's the case we register a dummy listener if there isn't one on
+  // the element already.
+  if (!CaretElement()->IsApzAware()) {
+    CaretElement()->AddEventListener(NS_LITERAL_STRING("touchstart"),
+                                     mDummyTouchListener, false);
+  }
+}
+
 void
 AccessibleCaret::InjectCaretElement(nsIDocument* aDocument)
 {
@@ -200,8 +212,7 @@ AccessibleCaret::InjectCaretElement(nsIDocument* aDocument)
   // InsertAnonymousContent will clone the element to make an AnonymousContent.
   // Since event listeners are not being cloned when cloning a node, we need to
   // add the listener here.
-  CaretElement()->AddEventListener(NS_LITERAL_STRING("touchstart"),
-                                   mDummyTouchListener, false);
+  EnsureApzAware();
 }
 
 already_AddRefed<Element>

layout/base/AccessibleCaret.h

@@ -136,6 +136,10 @@ public:
     return mCaretElementHolder->GetContentNode();
   }
 
+  // Ensures that the caret element is made "APZ aware" so that the APZ code
+  // doesn't scroll the page when the user is trying to drag the caret.
+  void EnsureApzAware();
+
 protected:
   // Argument aRect should be relative to CustomContentContainerFrame().
   void SetCaretElementStyle(const nsRect& aRect, float aZoomLevel);

layout/base/AccessibleCaretEventHub.cpp

@@ -401,6 +401,10 @@ AccessibleCaretEventHub::~AccessibleCaretEventHub()
 void
 AccessibleCaretEventHub::Init()
 {
+  if (mInitialized && mManager) {
+    mManager->OnFrameReconstruction();
+  }
+
   if (mInitialized || !mPresShell || !mPresShell->GetCanvasFrame() ||
       !mPresShell->GetCanvasFrame()->GetCustomContentContainer()) {
     return;

layout/base/AccessibleCaretManager.cpp

@@ -697,6 +697,13 @@ AccessibleCaretManager::OnKeyboardEvent()
   }
 }
 
+void
+AccessibleCaretManager::OnFrameReconstruction()
+{
+  mFirstCaret->EnsureApzAware();
+  mSecondCaret->EnsureApzAware();
+}
+
 Selection*
 AccessibleCaretManager::GetSelection() const
 {

layout/base/AccessibleCaretManager.h

@@ -98,6 +98,10 @@ public:
   // Handle key event.
   virtual void OnKeyboardEvent();
 
+  // The canvas frame holding the accessible caret anonymous content elements
+  // was reconstructed, resulting in the content elements getting cloned.
+  virtual void OnFrameReconstruction();
+
 protected:
   // This enum representing the number of AccessibleCarets on the screen.
   enum class CaretMode : uint8_t {