Retarget mouse event if the target is removed

third_party/WebKit/Source/core/input/PointerEventManager.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/input/PointerEventManager.h"
 
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/shadow/FlatTreeTraversal.h"
 #include "core/events/MouseEvent.h"
 #include "core/html/HTMLCanvasElement.h"
@@ skipping 61 matching lines @@
     HTMLCanvasElement* canvas = Traversal<HTMLCanvasElement>::firstAncestorOrSelf(*element);
     // In this case, the event target is canvas and mouse rerouting doesn't happen.
     if (canvas == element)
         return mouseEvent;
     String region = canvas->getIdFromControl(element);
     PlatformMouseEvent newMouseEvent = mouseEvent;
     newMouseEvent.setRegion(region);
     return newMouseEvent;
 }
 
+void buildAncestorChain(
+    EventTarget* target,
+    HeapVector<Member<Node>, 20>* ancestors)
+{
+    if (!isInDocument(target))
+        return;
+    Node* targetNode = target->toNode();
+    DCHECK(targetNode);
+    targetNode->updateDistribution();
+    // Index 0 element in the ancestors arrays will be the corresponding
+    // target. So the root of their document will be their last element.
+    for (Node* node = targetNode; node; node = FlatTreeTraversal::parent(*node))
+        ancestors->append(node);
+}
+
 void buildAncestorChainsAndFindCommonAncestors(
     EventTarget* exitedTarget, EventTarget* enteredTarget,
     HeapVector<Member<Node>, 20>* exitedAncestorsOut,
     HeapVector<Member<Node>, 20>* enteredAncestorsOut,
     size_t* exitedAncestorsCommonParentIndexOut,
     size_t* enteredAncestorsCommonParentIndexOut)
 {
     DCHECK(exitedAncestorsOut);
     DCHECK(enteredAncestorsOut);
     DCHECK(exitedAncestorsCommonParentIndexOut);
     DCHECK(enteredAncestorsCommonParentIndexOut);
 
-    // Index 0 element in the ancestors arrays will be the corresponding
-    // target. So the root of their document will be their last element.
-
-    if (isInDocument(exitedTarget)) {
-        Node* exitedNode = exitedTarget->toNode();
-        DCHECK(exitedNode);
-        exitedNode->updateDistribution();
-        for (Node* node = exitedNode; node; node = FlatTreeTraversal::parent(*node))
-            exitedAncestorsOut->append(node);
-    }
-
-    if (isInDocument(enteredTarget)) {
-        Node* enteredNode = enteredTarget->toNode();
-        DCHECK(enteredNode);
-        enteredNode->updateDistribution();
-        for (Node* node = enteredNode; node; node = FlatTreeTraversal::parent(*node))
-            enteredAncestorsOut->append(node);
-    }
+    buildAncestorChain(exitedTarget, exitedAncestorsOut);
+    buildAncestorChain(enteredTarget, enteredAncestorsOut);
 
     *exitedAncestorsCommonParentIndexOut = exitedAncestorsOut->size();
     *enteredAncestorsCommonParentIndexOut = enteredAncestorsOut->size();
     while (*exitedAncestorsCommonParentIndexOut > 0
         && *enteredAncestorsCommonParentIndexOut > 0) {
         if ((*exitedAncestorsOut)[(*exitedAncestorsCommonParentIndexOut)-1]
             != (*enteredAncestorsOut)[(*enteredAncestorsCommonParentIndexOut)-1])
             break;
         (*exitedAncestorsCommonParentIndexOut)--;
         (*enteredAncestorsCommonParentIndexOut)--;
@@ skipping 323 matching lines @@
 
     if (result != WebInputEventResult::NotHandled
         && pointerEvent->type() == EventTypeNames::pointerdown
         && pointerEvent->isPrimary()) {
         m_preventMouseEventForPointerType[toPointerTypeIndex(
             mouseEvent.pointerProperties().pointerType)] = true;
     }
 
     if (pointerEvent->isPrimary() && !m_preventMouseEventForPointerType[toPointerTypeIndex(
         mouseEvent.pointerProperties().pointerType)]) {
+        EventTarget* mouseTarget = effectiveTarget;

[mustaq, 2016/05/05 15:31:02]

Can we ever have both of these false?
- isInDocument(effectiveTarget)
- pointerEvent->hasEventPath()

Can't we just iterate on pointerEvent->eventPath() instead of relying on
effectiveTarget at all?

[Navid Zolghadr, 2016/05/06 15:47:20]

When pointer event feature is not enabled we are not sending the pointe event
and as the result eventPath is null and we can not always rely on that. I added
a comment to make it more clear.

+        if (!isInDocument(mouseTarget) && pointerEvent->hasEventPath()) {
+            for (size_t i = 0; i < pointerEvent->eventPath().size(); i++) {
+                if (isInDocument(pointerEvent->eventPath()[i].node())) {
+                    mouseTarget = pointerEvent->eventPath()[i].node();
+                    break;
+                }
+            }
+        }
         result = EventHandler::mergeEventResult(result,
-            dispatchMouseEvent(effectiveTarget, mouseEventType, mouseEvent,
+            dispatchMouseEvent(mouseTarget, mouseEventType, mouseEvent,
             nullptr, clickCount));
     }
 
     if (pointerEvent->buttons() == 0) {
         releasePointerCapture(pointerEvent->pointerId());
         if (pointerEvent->isPrimary()) {
             m_preventMouseEventForPointerType[toPointerTypeIndex(
                 mouseEvent.pointerProperties().pointerType)] = false;
         }
     }
@@ skipping 187 matching lines @@
 
 DEFINE_TRACE(PointerEventManager)
 {
     visitor->trace(m_nodeUnderPointer);
     visitor->trace(m_pointerCaptureTarget);
     visitor->trace(m_pendingPointerCaptureTarget);
 }
 
 
 } // namespace blink