Bug 1695574 - Make `PresShell::EventHandler::HandleEventUsingCoordina…

…tes` keep handling touch events after preceding pointer event target is removed r=smaug,edgar,dom-core

As far as investigating the behavior of the other browsers, touch events are
dispatched the same target as the preceding `pointerdown` even after the target
is removed from the DOM tree.  However, the following pointer events are
dispatched on the target as usual (i.e., the element under the pointer except
when the pointer is captured).  However, our code stops handling touch events
if the preceding `pointerdown` removes the target and not dispatching
`touchstart` causes not dispatching the following touch events so that no
`click` event is fired.

This patch makes the touch event dispatching path work without frame and
keep handling even with an orphan event target.

Differential Revision: https://phabricator.services.mozilla.com/D202811

dom/events/PointerEventHandler.cpp

@@ -610,15 +610,16 @@ EventMessage PointerEventHandler::ToPointerEventMessage(
 
 /* static */
 void PointerEventHandler::DispatchPointerFromMouseOrTouch(
-    PresShell* aShell, nsIFrame* aFrame, nsIContent* aContent,
-    WidgetGUIEvent* aEvent, bool aDontRetargetEvents, nsEventStatus* aStatus,
-    nsIContent** aTargetContent) {
-  MOZ_ASSERT(aFrame || aContent);
-  MOZ_ASSERT(aEvent);
+    PresShell* aShell, nsIFrame* aEventTargetFrame,
+    nsIContent* aEventTargetContent, WidgetGUIEvent* aMouseOrTouchEvent,
+    bool aDontRetargetEvents, nsEventStatus* aStatus,
+    nsIContent** aMouseOrTouchEventTarget /* = nullptr */) {
+  MOZ_ASSERT(aEventTargetFrame || aEventTargetContent);
+  MOZ_ASSERT(aMouseOrTouchEvent);
 
   EventMessage pointerMessage = eVoidEvent;
-  if (aEvent->mClass == eMouseEventClass) {
-    WidgetMouseEvent* mouseEvent = aEvent->AsMouseEvent();
+  if (aMouseOrTouchEvent->mClass == eMouseEventClass) {
+    WidgetMouseEvent* mouseEvent = aMouseOrTouchEvent->AsMouseEvent();
     // Don't dispatch pointer events caused by a mouse when simulating touch
     // devices in RDM.
     Document* doc = aShell->GetDocument();
@@ -636,7 +637,7 @@ void PointerEventHandler::DispatchPointerFromMouseOrTouch(
     // 2. We don't synthesize pointer events for those events that are not
     //    dispatched to DOM.
     if (!mouseEvent->convertToPointer ||
-        !aEvent->IsAllowedToDispatchDOMEvent()) {
+        !aMouseOrTouchEvent->IsAllowedToDispatchDOMEvent()) {
       return;
     }
 
@@ -648,20 +649,20 @@ void PointerEventHandler::DispatchPointerFromMouseOrTouch(
     InitPointerEventFromMouse(&event, mouseEvent, pointerMessage);
     event.convertToPointer = mouseEvent->convertToPointer = false;
     RefPtr<PresShell> shell(aShell);
-    if (!aFrame) {
-      shell = PresShell::GetShellForEventTarget(nullptr, aContent);
+    if (!aEventTargetFrame) {
+      shell = PresShell::GetShellForEventTarget(nullptr, aEventTargetContent);
       if (!shell) {
         return;
       }
     }
-    PreHandlePointerEventsPreventDefault(&event, aEvent);
+    PreHandlePointerEventsPreventDefault(&event, aMouseOrTouchEvent);
     // Dispatch pointer event to the same target which is found by the
     // corresponding mouse event.
-    shell->HandleEventWithTarget(&event, aFrame, aContent, aStatus, true,
-                                 aTargetContent);
-    PostHandlePointerEventsPreventDefault(&event, aEvent);
-  } else if (aEvent->mClass == eTouchEventClass) {
-    WidgetTouchEvent* touchEvent = aEvent->AsTouchEvent();
+    shell->HandleEventWithTarget(&event, aEventTargetFrame, aEventTargetContent,
+                                 aStatus, true, aMouseOrTouchEventTarget);
+    PostHandlePointerEventsPreventDefault(&event, aMouseOrTouchEvent);
+  } else if (aMouseOrTouchEvent->mClass == eTouchEventClass) {
+    WidgetTouchEvent* touchEvent = aMouseOrTouchEvent->AsTouchEvent();
     // loop over all touches and dispatch pointer events on each touch
     // copy the event
     pointerMessage = PointerEventHandler::ToPointerEventMessage(touchEvent);
@@ -681,7 +682,7 @@ void PointerEventHandler::DispatchPointerFromMouseOrTouch(
       InitPointerEventFromTouch(event, *touchEvent, *touch, i == 0);
       event.convertToPointer = touch->convertToPointer = false;
       event.mCoalescedWidgetEvents = touch->mCoalescedWidgetEvents;
-      if (aEvent->mMessage == eTouchStart) {
+      if (aMouseOrTouchEvent->mMessage == eTouchStart) {
         // We already did hit test for touchstart in PresShell. We should
         // dispatch pointerdown to the same target as touchstart.
         nsCOMPtr<nsIContent> content =
@@ -696,18 +697,22 @@ void PointerEventHandler::DispatchPointerFromMouseOrTouch(
           continue;
         }
 
-        PreHandlePointerEventsPreventDefault(&event, aEvent);
+        PreHandlePointerEventsPreventDefault(&event, aMouseOrTouchEvent);
         shell->HandleEventWithTarget(&event, frame, content, aStatus, true,
-                                     nullptr);
-        PostHandlePointerEventsPreventDefault(&event, aEvent);
+                                     aMouseOrTouchEventTarget);
+        PostHandlePointerEventsPreventDefault(&event, aMouseOrTouchEvent);
       } else {
         // We didn't hit test for other touch events. Spec doesn't mention that
         // all pointer events should be dispatched to the same target as their
         // corresponding touch events. Call PresShell::HandleEvent so that we do
         // hit test for pointer events.
-        PreHandlePointerEventsPreventDefault(&event, aEvent);
-        shell->HandleEvent(aFrame, &event, aDontRetargetEvents, aStatus);
-        PostHandlePointerEventsPreventDefault(&event, aEvent);
+        // FIXME: If aDontRetargetEvents is true and the event is fired on
+        // different document, we cannot track the pointer event target when
+        // it's removed from the tree.
+        PreHandlePointerEventsPreventDefault(&event, aMouseOrTouchEvent);
+        shell->HandleEvent(aEventTargetFrame, &event, aDontRetargetEvents,
+                           aStatus);
+        PostHandlePointerEventsPreventDefault(&event, aMouseOrTouchEvent);
       }
     }
   }

dom/events/PointerEventHandler.h

@@ -168,11 +168,39 @@ class PointerEventHandler final {
   static void PostHandlePointerEventsPreventDefault(
       WidgetPointerEvent* aPointerEvent, WidgetGUIEvent* aMouseOrTouchEvent);
 
-  MOZ_CAN_RUN_SCRIPT
-  static void DispatchPointerFromMouseOrTouch(
-      PresShell* aShell, nsIFrame* aFrame, nsIContent* aContent,
-      WidgetGUIEvent* aEvent, bool aDontRetargetEvents, nsEventStatus* aStatus,
-      nsIContent** aTargetContent);
+  /**
+   * Dispatch a pointer event for aMouseOrTouchEvent to aEventTargetContent.
+   *
+   * @param aShell              The PresShell which is handling the event.
+   * @param aEventTargetFrame   The frame for aEventTargetContent.
+   * @param aEventTargetContent The event target node.
+   * @param aMouseOrTouchEvent  A mouse or touch event.
+   * @param aDontRetargetEvents If true, this won't dispatch event with
+   *                            different PresShell from aShell.  Otherwise,
+   *                            pointer events may be fired on different
+   *                            document if and only if aMouseOrTOuchEvent is a
+   *                            touch event except eTouchStart.
+   * @param aState              [out] The result of the pointer event.
+   * @param aMouseOrTouchEventTarget
+   *                            [out] The event target for the following mouse
+   *                            or touch event. If aEventTargetContent has not
+   *                            been removed from the tree, this is always set
+   *                            to it. If aEventTargetContent is removed from
+   *                            the tree and aMouseOrTouchEvent is a mouse
+   *                            event, this is set to inclusive ancestor of
+   *                            aEventTargetContent which is still connected.
+   *                            If aEventTargetContent is removed from the tree
+   *                            and aMouseOrTouchEvent is a touch event, this is
+   *                            set to aEventTargetContent because touch event
+   *                            should be dispatched even on disconnected node.
+   *                            FIXME: If the event is a touch event but the
+   *                            message is not eTouchStart, this won't be set.
+   */
+  MOZ_CAN_RUN_SCRIPT static void DispatchPointerFromMouseOrTouch(
+      PresShell* aShell, nsIFrame* aEventTargetFrame,
+      nsIContent* aEventTargetContent, WidgetGUIEvent* aMouseOrTouchEvent,
+      bool aDontRetargetEvents, nsEventStatus* aStatus,
+      nsIContent** aMouseOrTouchEventTarget = nullptr);
 
   static void InitPointerEventFromMouse(WidgetPointerEvent* aPointerEvent,
                                         WidgetMouseEvent* aMouseEvent,

layout/base/PresShell.cpp

@@ -580,20 +580,35 @@ class MOZ_STACK_CLASS AutoPointerEventTargetUpdater final {
     mShell = aShell;
     mWeakFrame = aFrame;
     mTargetContent = aTargetContent;
-    aShell->mPointerEventTarget = aFrame->GetContent();
+    mFromTouch = aEvent->AsPointerEvent()->mFromTouchEvent;
+    mOriginalPointerEventTarget = aShell->mPointerEventTarget =
+        aFrame->GetContent();
   }
 
   ~AutoPointerEventTargetUpdater() {
     if (!mTargetContent || !mShell || mWeakFrame.IsAlive()) {
       return;
     }
-    mShell->mPointerEventTarget.swap(*mTargetContent);
+    if (mFromTouch) {
+      // If the source event is a touch event, the touch event target should
+      // always be same target as preceding ePointerDown.  Therefore, we should
+      // always set it back to the original event target.
+      mOriginalPointerEventTarget.swap(*mTargetContent);
+    } else {
+      // If the source event is not a touch event (must be a mouse event in
+      // this case), the event should be fired on the closest inclusive ancestor
+      // of the pointer event target which is still connected.  The mutations
+      // are tracked by PresShell::ContentRemoved.  Therefore, we should set it.
+      mShell->mPointerEventTarget.swap(*mTargetContent);
+    }
   }
 
  private:
   RefPtr<PresShell> mShell;
+  nsCOMPtr<nsIContent> mOriginalPointerEventTarget;
   AutoWeakFrame mWeakFrame;
   nsIContent** mTargetContent;
+  bool mFromTouch = false;
 };
 
 bool PresShell::sDisableNonTestMouseEvents = false;
@@ -6890,18 +6905,13 @@ PresShell* PresShell::GetShellForTouchEvent(WidgetGUIEvent* aEvent) {
           return nullptr;
         }
 
-        nsCOMPtr<nsIContent> content = do_QueryInterface(oldTouch->GetTarget());
+        nsIContent* const content =
+            nsIContent::FromEventTargetOrNull(oldTouch->GetTarget());
         if (!content) {
           return nullptr;
         }
 
-        nsIFrame* contentFrame = content->GetPrimaryFrame();
-        if (!contentFrame) {
-          return nullptr;
-        }
-
-        PresShell* presShell = contentFrame->PresContext()->GetPresShell();
-        if (presShell) {
+        if (PresShell* const presShell = content->OwnerDoc()->GetPresShell()) {
           return presShell;
         }
       }
@@ -7251,12 +7261,6 @@ nsresult PresShell::EventHandler::HandleEventUsingCoordinates(
     return NS_OK;
   }
 
-  // frame could be null after dispatching pointer events.
-  // XXX Despite of this comment, we update the event target data outside
-  //     DispatchPrecedingPointerEvent().  Can we make it call
-  //     UpdateTouchEventTarget()?
-  eventTargetData.UpdateTouchEventTarget(aGUIEvent);
-
   // Handle the event in the correct shell.
   // We pass the subshell's root frame as the frame to start from. This is
   // the only correct alternative; if the event was captured then it
@@ -7448,41 +7452,58 @@ bool PresShell::EventHandler::DispatchPrecedingPointerEvent(
 
   AutoWeakFrame weakTargetFrame(targetFrame);
   AutoWeakFrame weakFrame(aEventTargetData->GetFrame());
-  nsCOMPtr<nsIContent> content(aEventTargetData->GetContent());
+  nsCOMPtr<nsIContent> pointerEventTargetContent(
+      aEventTargetData->GetContent());
   RefPtr<PresShell> presShell(aEventTargetData->mPresShell);
-  nsCOMPtr<nsIContent> targetContent;
+  nsCOMPtr<nsIContent> mouseOrTouchEventTargetContent;
   PointerEventHandler::DispatchPointerFromMouseOrTouch(
-      presShell, aEventTargetData->GetFrame(), content, aGUIEvent,
-      aDontRetargetEvents, aEventStatus, getter_AddRefs(targetContent));
+      presShell, aEventTargetData->GetFrame(), pointerEventTargetContent,
+      aGUIEvent, aDontRetargetEvents, aEventStatus,
+      getter_AddRefs(mouseOrTouchEventTargetContent));
 
   // If the target frame is alive, the caller should keep handling the event
   // unless event target frame is destroyed.
-  if (weakTargetFrame.IsAlive()) {
-    return weakFrame.IsAlive();
+  if (weakTargetFrame.IsAlive() && weakFrame.IsAlive()) {
+    aEventTargetData->UpdateTouchEventTarget(aGUIEvent);
+    return true;
   }
 
-  // If the event is not a mouse event, the caller should keep handling the
-  // event unless event target frame is destroyed.  Note that this case is
-  // not defined by the spec.
-  if (aGUIEvent->mClass != eMouseEventClass) {
-    return weakFrame.IsAlive();
+  presShell->FlushPendingNotifications(FlushType::Layout);
+  if (MOZ_UNLIKELY(mPresShell->IsDestroying())) {
+    return false;
   }
 
-  // Spec defines that mouse events must be dispatched to the same target as
-  // the pointer event. If the target is no longer participating in its
-  // ownerDocument's tree, fire the event at the original target's nearest
-  // ancestor node
-  if (!targetContent) {
+  // The spec defines that mouse events must be dispatched to the same target as
+  // the pointer event.
+  // The Touch Events spec defines that touch events must be dispatched to the
+  // same target as touch start and the other browsers dispatch touch events
+  // even if the touch event target is not connected to the document.
+  // Retargetting the event is handled by AutoPointerEventTargetUpdater and
+  // mouseOrTouchEventTargetContent stores the result.
+
+  // If the target is no longer participating in its ownerDocument's tree,
+  // fire the event at the original target's nearest ancestor node.
+  if (!mouseOrTouchEventTargetContent) {
+    MOZ_ASSERT(aGUIEvent->mClass == eMouseEventClass);
     return false;
   }
 
-  aEventTargetData->SetFrameAndContent(targetContent->GetPrimaryFrame(),
-                                       targetContent);
-  aEventTargetData->mPresShell = PresShell::GetShellForEventTarget(
-      aEventTargetData->GetFrame(), aEventTargetData->GetContent());
+  aEventTargetData->SetFrameAndContent(
+      mouseOrTouchEventTargetContent->GetPrimaryFrame(),
+      mouseOrTouchEventTargetContent);
+  aEventTargetData->mPresShell =
+      mouseOrTouchEventTargetContent->IsInComposedDoc()
+          ? PresShell::GetShellForEventTarget(aEventTargetData->GetFrame(),
+                                              aEventTargetData->GetContent())
+          : mouseOrTouchEventTargetContent->OwnerDoc()->GetPresShell();
 
   // If new target PresShel is not found, we cannot keep handling the event.
-  return !!aEventTargetData->mPresShell;
+  if (!aEventTargetData->mPresShell) {
+    return false;
+  }
+
+  aEventTargetData->UpdateTouchEventTarget(aGUIEvent);
+  return true;
 }
 
 /**
@@ -12032,7 +12053,7 @@ void PresShell::EventHandler::EventTargetData::UpdateTouchEventTarget(
     nsIFrame* newFrame =
         TouchManager::SuppressInvalidPointsAndGetTargetedFrame(touchEvent);
     if (!newFrame) {
-      return;  // XXX Why don't we stop handling the event in this case?
+      return;
     }
     SetFrameAndComputePresShellAndContent(newFrame, aGUIEvent);
     return;

layout/base/TouchManager.cpp

@@ -174,17 +174,43 @@ nsIFrame* TouchManager::SuppressInvalidPointsAndGetTargetedFrame(
   }
 
   nsIFrame* frame = nullptr;
-  for (int32_t i = aEvent->mTouches.Length(); i;) {
+  for (uint32_t i = aEvent->mTouches.Length(); i;) {
     --i;
     dom::Touch* touch = aEvent->mTouches[i];
     if (TouchManager::HasCapturedTouch(touch->Identifier())) {
       continue;
     }
 
     MOZ_ASSERT(touch->mOriginalTarget);
-    nsCOMPtr<nsIContent> targetContent = do_QueryInterface(touch->GetTarget());
-    nsIFrame* targetFrame =
-        targetContent ? targetContent->GetPrimaryFrame() : nullptr;
+    nsIContent* const targetContent =
+        nsIContent::FromEventTargetOrNull(touch->GetTarget());
+    if (MOZ_UNLIKELY(!targetContent)) {
+      touch->mIsTouchEventSuppressed = true;
+      continue;
+    }
+
+    // Even if the target content is not connected, we should dispatch the touch
+    // start event except when the target content is owned by different
+    // document.
+    if (MOZ_UNLIKELY(!targetContent->IsInComposedDoc())) {
+      if (anyTarget && anyTarget->OwnerDoc() != targetContent->OwnerDoc()) {
+        touch->mIsTouchEventSuppressed = true;
+        continue;
+      }
+      if (!anyTarget) {
+        anyTarget = targetContent;
+      }
+      touch->SetTouchTarget(targetContent->GetAsElementOrParentElement());
+      if (PresShell* const presShell =
+              targetContent->OwnerDoc()->GetPresShell()) {
+        if (nsIFrame* rootFrame = presShell->GetRootFrame()) {
+          frame = rootFrame;
+        }
+      }
+      continue;
+    }
+
+    nsIFrame* targetFrame = targetContent->GetPrimaryFrame();
     if (targetFrame && !anyTarget) {
       anyTarget = targetContent;
     } else {
@@ -208,10 +234,12 @@ nsIFrame* TouchManager::SuppressInvalidPointsAndGetTargetedFrame(
         touch->mIsTouchEventSuppressed = true;
       } else {
         targetFrame = newTargetFrame;
-        targetFrame->GetContentForEvent(aEvent, getter_AddRefs(targetContent));
-        touch->SetTouchTarget(targetContent
-                                  ? targetContent->GetAsElementOrParentElement()
-                                  : nullptr);
+        nsCOMPtr<nsIContent> newTargetContent;
+        targetFrame->GetContentForEvent(aEvent,
+                                        getter_AddRefs(newTargetContent));
+        touch->SetTouchTarget(
+            newTargetContent ? newTargetContent->GetAsElementOrParentElement()
+                             : nullptr);
       }
     }
     if (targetFrame) {

testing/web-platform/meta/pointerevents/pointerup_after_pointerdown_target_removed.html.ini

@@ -1,8 +1,3 @@
 [pointerup_after_pointerdown_target_removed.html?pen]
   [pointerup event from pen fired after pointerdown target is removed]
     expected: FAIL
-
-
-[pointerup_after_pointerdown_target_removed.html?touch]
-  [pointerup event from touch fired after pointerdown target is removed]
-    expected: FAIL