Issue #2030 - Dispatch click on common interactive ancestor if mousdown/up are not on the same element

For example, if the mouse is dragged from one element to another while
staying inside the same button, dispatch from their common ancestor

dom/base/nsContentUtils.cpp

@@ -2377,6 +2377,56 @@ nsContentUtils::GetCommonAncestor(nsINode* aNode1,
   return parent;
 }
 
+// static
+nsINode*
+nsContentUtils::GetCommonAncestorUnderInteractiveContent(nsINode* aNode1,
+                                                         nsINode* aNode2)
+{
+  if (!aNode1 || !aNode2) {
+    return nullptr;
+  }
+
+  if (aNode1 == aNode2) {
+    return aNode1;
+  }
+
+  // Build the chain of parents
+  AutoTArray<nsINode*, 30> parents1;
+  do {
+    parents1.AppendElement(aNode1);
+    if (aNode1->IsElement() &&
+        aNode1->AsElement()->IsInteractiveHTMLContent(true)) {
+      break;
+    }
+    aNode1 = aNode1->GetFlattenedTreeParentNode();
+  } while (aNode1);
+
+  AutoTArray<nsINode*, 30> parents2;
+  do {
+    parents2.AppendElement(aNode2);
+    if (aNode2->IsElement() &&
+        aNode2->AsElement()->IsInteractiveHTMLContent(true)) {
+      break;
+    }
+    aNode2 = aNode2->GetFlattenedTreeParentNode();
+  } while (aNode2);
+
+  // Find where the parent chain differs
+  uint32_t pos1 = parents1.Length();
+  uint32_t pos2 = parents2.Length();
+  nsINode* parent = nullptr;
+  for (uint32_t len = std::min(pos1, pos2); len > 0; --len) {
+    nsINode* child1 = parents1.ElementAt(--pos1);
+    nsINode* child2 = parents2.ElementAt(--pos2);
+    if (child1 != child2) {
+      break;
+    }
+    parent = child1;
+  }
+
+  return parent;
+}
+
 /* static */
 bool
 nsContentUtils::PositionIsBefore(nsINode* aNode1, nsINode* aNode2)

dom/base/nsContentUtils.h

@@ -324,6 +324,15 @@ public:
   static nsINode* GetCommonAncestor(nsINode* aNode1,
                                     nsINode* aNode2);
 
+  /**
+   * Returns the common ancestor under interactive content, if any.
+   * If neither one has interactive content as ancestor, common ancestor will be
+   * returned. If only one has interactive content as ancestor, null will be
+   * returned. If the nodes are the same, that node is returned.
+   */
+  static nsINode* GetCommonAncestorUnderInteractiveContent(nsINode* aNode1,
+                                                           nsINode* aNode2);
+
   /**
    * Returns true if aNode1 is before aNode2 in the same connected
    * tree.

dom/events/Event.cpp

@@ -194,6 +194,11 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Event)
       default:
         break;
     }
+
+    if (WidgetMouseEvent* mouseEvent = tmp->mEvent->AsMouseEvent()) {
+      NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mEvent->mClickTarget");
+      cb.NoteXPCOMChild(mouseEvent->mClickTarget);
+    }
   }
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPresContext)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mExplicitOriginalTarget)

dom/events/EventStateManager.cpp

@@ -434,11 +434,8 @@ NS_IMPL_CYCLE_COLLECTION(EventStateManager,
                          mGestureDownContent,
                          mGestureDownFrameOwner,
                          mLastLeftMouseDownContent,
-                         mLastLeftMouseDownContentParent,
                          mLastMiddleMouseDownContent,
-                         mLastMiddleMouseDownContentParent,
                          mLastRightMouseDownContent,
-                         mLastRightMouseDownContentParent,
                          mActiveContent,
                          mHoverContent,
                          mURLTargetContent,
@@ -4576,16 +4573,13 @@ EventStateManager::SetClickCount(WidgetMouseEvent* aEvent,
                                  nsEventStatus* aStatus)
 {
   nsCOMPtr<nsIContent> mouseContent;
-  nsIContent* mouseContentParent = nullptr;
   if (mCurrentTarget) {
     mCurrentTarget->GetContentForEvent(aEvent, getter_AddRefs(mouseContent));
   }
-  if (mouseContent) {
+  if (mouseContent && mouseContent->IsNodeOfType(nsINode::eTEXT)) {
-    if (mouseContent->IsNodeOfType(nsINode::eTEXT)) {
+    nsINode* parent = mouseContent->GetFlattenedTreeParentNode();
-      mouseContent = mouseContent->GetParent();
+    if (parent && parent->IsContent()) {
-    }
+      mouseContent = parent->AsContent();
-    if (mouseContent && mouseContent->IsRootOfNativeAnonymousSubtree()) {
-      mouseContentParent = mouseContent->GetParent();
     }
   }
 
@@ -4593,54 +4587,51 @@ EventStateManager::SetClickCount(WidgetMouseEvent* aEvent,
   case WidgetMouseEvent::eLeftButton:
     if (aEvent->mMessage == eMouseDown) {
       mLastLeftMouseDownContent = mouseContent;
-      mLastLeftMouseDownContentParent = mouseContentParent;
     } else if (aEvent->mMessage == eMouseUp) {
-      if (mLastLeftMouseDownContent == mouseContent ||
+      aEvent->mClickTarget =
-          mLastLeftMouseDownContentParent == mouseContent ||
+        nsContentUtils::GetCommonAncestorUnderInteractiveContent(
-          mLastLeftMouseDownContent == mouseContentParent) {
+          mouseContent, mLastLeftMouseDownContent);
+      if (aEvent->mClickTarget) {
         aEvent->mClickCount = mLClickCount;
         mLClickCount = 0;
       } else {
         aEvent->mClickCount = 0;
       }
       mLastLeftMouseDownContent = nullptr;
-      mLastLeftMouseDownContentParent = nullptr;
     }
     break;
 
   case WidgetMouseEvent::eMiddleButton:
     if (aEvent->mMessage == eMouseDown) {
       mLastMiddleMouseDownContent = mouseContent;
-      mLastMiddleMouseDownContentParent = mouseContentParent;
     } else if (aEvent->mMessage == eMouseUp) {
-      if (mLastMiddleMouseDownContent == mouseContent ||
+      aEvent->mClickTarget =
-          mLastMiddleMouseDownContentParent == mouseContent ||
+        nsContentUtils::GetCommonAncestorUnderInteractiveContent(
-          mLastMiddleMouseDownContent == mouseContentParent) {
+          mouseContent, mLastMiddleMouseDownContent);
+      if (aEvent->mClickTarget) {
         aEvent->mClickCount = mMClickCount;
         mMClickCount = 0;
       } else {
         aEvent->mClickCount = 0;
       }
       mLastMiddleMouseDownContent = nullptr;
-      mLastMiddleMouseDownContentParent = nullptr;
     }
     break;
 
   case WidgetMouseEvent::eRightButton:
     if (aEvent->mMessage == eMouseDown) {
       mLastRightMouseDownContent = mouseContent;
-      mLastRightMouseDownContentParent = mouseContentParent;
     } else if (aEvent->mMessage == eMouseUp) {
-      if (mLastRightMouseDownContent == mouseContent ||
+      aEvent->mClickTarget =
-          mLastRightMouseDownContentParent == mouseContent ||
+        nsContentUtils::GetCommonAncestorUnderInteractiveContent(
-          mLastRightMouseDownContent == mouseContentParent) {
+          mouseContent, mLastRightMouseDownContent);
+      if (aEvent->mClickTarget) {
         aEvent->mClickCount = mRClickCount;
         mRClickCount = 0;
       } else {
         aEvent->mClickCount = 0;
       }
       mLastRightMouseDownContent = nullptr;
-      mLastRightMouseDownContentParent = nullptr;
     }
     break;
   }
@@ -4662,7 +4653,7 @@ EventStateManager::EventCausesClickEvents(const WidgetMouseEvent& aMouseEvent)
   }
   // If mouse is still over same element, clickcount will be > 1.
   // If it has moved it will be zero, so no click.
-  if (!aMouseEvent.mClickCount) {
+  if (!aMouseEvent.mClickCount || !aMouseEvent.mClickTarget) {
     return false;
   }
   // Check that the window isn't disabled before firing a click
@@ -4681,7 +4672,7 @@ EventStateManager::InitAndDispatchClickEvent(WidgetMouseEvent* aMouseUpEvent,
 {
   MOZ_ASSERT(aMouseUpEvent);
   MOZ_ASSERT(EventCausesClickEvents(*aMouseUpEvent));
-  MOZ_ASSERT(aMouseUpContent || aCurrentTarget || aOverrideClickTarget);
+  MOZ_ASSERT(aMouseUpContent || aCurrentTarget);
 
   WidgetMouseEvent event(aMouseUpEvent->IsTrusted(), aMessage,
                          aMouseUpEvent->mWidget, WidgetMouseEvent::eReal);
@@ -4695,6 +4686,10 @@ EventStateManager::InitAndDispatchClickEvent(WidgetMouseEvent* aMouseUpEvent,
   event.button = aMouseUpEvent->button;
   event.inputSource = aMouseUpEvent->inputSource;
 
+  if (!aMouseUpContent->IsInComposedDoc()) {
+    return NS_OK;
+  }
+
   // Use local event status for each click event dispatching since it'll be
   // cleared by EventStateManager::PreHandleEvent().  Therefore, dispatching
   // an event means that previous event status will be ignored.
@@ -4730,22 +4725,12 @@ EventStateManager::PostHandleMouseUp(WidgetMouseEvent* aMouseUpEvent,
     return NS_OK;
   }
 
-  nsCOMPtr<nsIContent> mouseUpContent = GetEventTargetContent(aMouseUpEvent);
+  nsCOMPtr<nsIContent> clickTarget = do_QueryInterface(aMouseUpEvent->mClickTarget);
-  // Click events apply to *elements* not nodes. At this point the target
+  NS_ENSURE_STATE(clickTarget);
-  // content may have been reset to some non-element content, and so we need
-  // to walk up the closest ancestor element, just like we do in
-  // nsPresShell::HandlePositionedEvent.
-  while (mouseUpContent && !mouseUpContent->IsElement()) {
-    mouseUpContent = mouseUpContent->GetFlattenedTreeParent();
-  }
-
-  if (!mouseUpContent && !mCurrentTarget) {
-    return NS_OK;
-  }
 
   // Fire click events if the event target is still available.
   nsresult rv = DispatchClickEvents(presShell, aMouseUpEvent, aStatus,
-                                    mouseUpContent);
+                                    clickTarget);
   if (NS_WARN_IF(NS_FAILED(rv))) {
     return rv;
   }
@@ -4756,13 +4741,13 @@ nsresult
 EventStateManager::DispatchClickEvents(nsIPresShell* aPresShell,
                                        WidgetMouseEvent* aMouseUpEvent,
                                        nsEventStatus* aStatus,
-                                       nsIContent* aMouseUpContent)
+                                       nsIContent* aClickTarget)
 {
   MOZ_ASSERT(aPresShell);
   MOZ_ASSERT(aMouseUpEvent);
   MOZ_ASSERT(EventCausesClickEvents(*aMouseUpEvent));
   MOZ_ASSERT(aStatus);
-  MOZ_ASSERT(aMouseUpContent || mCurrentTarget || aOverrideClickTarget);
+  MOZ_ASSERT(aClickTarget);
 
   bool notDispatchToContents =
    (aMouseUpEvent->button == WidgetMouseEvent::eMiddleButton ||
@@ -4770,12 +4755,10 @@ EventStateManager::DispatchClickEvents(nsIPresShell* aPresShell,
 
   bool fireAuxClick = notDispatchToContents;
 
-
+  nsWeakFrame currentTarget = aClickTarget->GetPrimaryFrame();
-  // HandleEvent clears out mCurrentTarget which we might need again
-  nsWeakFrame currentTarget = mCurrentTarget;
   nsresult ret =
     InitAndDispatchClickEvent(aMouseUpEvent, aStatus, eMouseClick,
-                              aPresShell, aMouseUpContent, currentTarget,
+                              aPresShell, aClickTarget, currentTarget,
                               notDispatchToContents);
   if (NS_WARN_IF(NS_FAILED(ret))) {
     return ret;
@@ -4783,21 +4766,20 @@ EventStateManager::DispatchClickEvents(nsIPresShell* aPresShell,
 
   // Fire double click event if click count is 2.
   if (aMouseUpEvent->mClickCount == 2 &&
-      aMouseUpContent && aMouseUpContent->IsInComposedDoc()) {
+      aClickTarget && aClickTarget->IsInComposedDoc()) {
     ret = InitAndDispatchClickEvent(aMouseUpEvent, aStatus, eMouseDoubleClick,
-                                    aPresShell, aMouseUpContent, currentTarget,
+                                    aPresShell, aClickTarget, currentTarget,
                                     notDispatchToContents);
     if (NS_WARN_IF(NS_FAILED(ret))) {
       return ret;
-
     }
   }
 
   // Fire auxclick even if necessary.
   if (fireAuxClick &&
-      aMouseUpContent && aMouseUpContent->IsInComposedDoc()) {
+      aClickTarget && aClickTarget->IsInComposedDoc()) {
     ret = InitAndDispatchClickEvent(aMouseUpEvent, aStatus, eMouseAuxClick,
-                                    aPresShell, aMouseUpContent, currentTarget,
+                                    aPresShell, aClickTarget, currentTarget,
                                     false);
     NS_WARNING_ASSERTION(NS_SUCCEEDED(ret), "Failed to dispatch eMouseAuxClick");
   }

dom/events/EventStateManager.h

@@ -1014,11 +1014,8 @@ private:
   uint16_t mGestureDownButtons;
 
   nsCOMPtr<nsIContent> mLastLeftMouseDownContent;
-  nsCOMPtr<nsIContent> mLastLeftMouseDownContentParent;
   nsCOMPtr<nsIContent> mLastMiddleMouseDownContent;
-  nsCOMPtr<nsIContent> mLastMiddleMouseDownContentParent;
   nsCOMPtr<nsIContent> mLastRightMouseDownContent;
-  nsCOMPtr<nsIContent> mLastRightMouseDownContentParent;
 
   nsCOMPtr<nsIContent> mActiveContent;
   nsCOMPtr<nsIContent> mHoverContent;

widget/MouseEvents.h

@@ -275,6 +275,10 @@ public:
     return result;
   }
 
+  // If during mouseup handling we detect that click event might need to be
+  // dispatched, this is setup to be the target of the click event.
+  nsCOMPtr<dom::EventTarget> mClickTarget;
+
   // mReason indicates the reason why the event is fired:
   // - Representing mouse operation.
   // - Synthesized for emulating mousemove event when the content under the