Bug 1466208 - part 4: Create PresShell::EventHandler::GetCapturingContentFor() to retrieve capturing content for specific event r=smaug

PresShell::HandleEvent() treats capturing content only when received event is
related to pointing device.  And it's used in 2 purposes.  One is for computing
to target document of coming event.  The other is for handling events using
coordinates.  Therefore, if we create a helper method to retrieve it, we can
move the variable into smaller blocks.

Differential Revision: https://phabricator.services.mozilla.com/D16954

--HG--
extra : moz-landing-system : lando

layout/base/PresShell.cpp

@@ -6520,12 +6520,6 @@ nsresult PresShell::EventHandler::HandleEvent(nsIFrame* aFrame,
     return NS_OK;
   }
 
-  nsIContent* capturingContent = ((aGUIEvent->mClass == ePointerEventClass ||
-                                   aGUIEvent->mClass == eWheelEventClass ||
-                                   aGUIEvent->HasMouseEventMessage())
-                                      ? nsIPresShell::GetCapturingContent()
-                                      : nullptr);
-
   RefPtr<Document> retargetEventDoc;
   if (!aDontRetargetEvents) {
     // key and IME related events should not cross top level window boundary.
@@ -6547,7 +6541,8 @@ nsresult PresShell::EventHandler::HandleEvent(nsIFrame* aFrame,
 
       retargetEventDoc = window->GetExtantDoc();
       if (!retargetEventDoc) return NS_OK;
-    } else if (capturingContent) {
+    } else if (nsIContent* capturingContent =
+                   EventHandler::GetCapturingContentFor(aGUIEvent)) {
       // if the mouse is being captured then retarget the mouse event at the
       // document that is being captured.
       retargetEventDoc = capturingContent->GetComposedDoc();
@@ -6611,6 +6606,11 @@ nsresult PresShell::EventHandler::HandleEvent(nsIFrame* aFrame,
   nsIFrame* frame = aFrame;
 
   if (aGUIEvent->IsUsingCoordinates()) {
+    // XXX Retrieving capturing content here.  However, some of the following
+    //     methods allow to run script.  So, isn't it possible the capturing
+    //     content outdated?
+    nsIContent* capturingContent =
+        EventHandler::GetCapturingContentFor(aGUIEvent);
     if (GetDocument()) {
       if (aGUIEvent->mClass == eTouchEventClass) {
         Document::UnlockPointer();
@@ -7156,6 +7156,16 @@ bool PresShell::EventHandler::MaybeHandleEventWithAccessibleCaret(
   return true;
 }
 
+// static
+nsIContent* PresShell::EventHandler::GetCapturingContentFor(
+    WidgetGUIEvent* aGUIEvent) {
+  return (aGUIEvent->mClass == ePointerEventClass ||
+          aGUIEvent->mClass == eWheelEventClass ||
+          aGUIEvent->HasMouseEventMessage())
+             ? nsIPresShell::GetCapturingContent()
+             : nullptr;
+}
+
 Document* PresShell::GetPrimaryContentDocument() {
   nsPresContext* context = GetPresContext();
   if (!context || !context->IsRoot()) {

layout/base/PresShell.h

@@ -574,6 +574,12 @@ class PresShell final : public nsIPresShell,
     static already_AddRefed<nsIURI> GetDocumentURIToCompareWithBlacklist(
         PresShell& aPresShell);
 
+    /**
+     * GetCapturingContentFor() returns capturing content for aGUIEvent.
+     * If aGUIEvent is not related to capturing, this returns nullptr.
+     */
+    static nsIContent* GetCapturingContentFor(WidgetGUIEvent* aGUIEvent);
+
     MOZ_CAN_RUN_SCRIPT
     nsresult RetargetEventToParent(WidgetGUIEvent* aGUIEvent,
                                    nsEventStatus* aEventStatus);