Bug 1466208 - part 9: Create PresShell::EventHandler::MaybeHandleEven…

…tWithAnotherPresShell() to handle event with another PresShell if necessary r=smaug

Let's move the redirection of coming event in
PresShell::EventHandler::HandleEvent() into a method.  This makes the caller
easier to read.

Differential Revision: https://phabricator.services.mozilla.com/D16959

layout/base/PresShell.cpp

@@ -6521,22 +6521,13 @@ nsresult PresShell::EventHandler::HandleEvent(nsIFrame* aFrame,
   }
 
   if (!aDontRetargetEvents) {
-    RefPtr<Document> retargetEventDoc;
-    if (!GetRetargetEventDocument(aGUIEvent,
-                                  getter_AddRefs(retargetEventDoc))) {
-      return NS_OK;  // Not need to return error.
-    }
-
-    if (retargetEventDoc) {
-      nsIFrame* frame =
-          GetFrameForHandlingEventWith(aGUIEvent, retargetEventDoc, aFrame);
-      if (!frame) {
-        return NS_OK;  // Not need to return error.
-      }
-      if (frame != aFrame) {
-        nsCOMPtr<nsIPresShell> shell = frame->PresContext()->GetPresShell();
-        return shell->HandleEvent(frame, aGUIEvent, true, aEventStatus);
-      }
+    // If aGUIEvent should be handled in another PresShell, we should call its
+    // HandleEvent() and do nothing here.
+    nsresult rv = NS_OK;
+    if (MaybeHandleEventWithAnotherPresShell(aFrame, aGUIEvent, aEventStatus,
+                                             &rv)) {
+      // Handled by another PresShell or nobody can handle the event.
+      return rv;
     }
   }
 
@@ -7220,6 +7211,48 @@ nsIFrame* PresShell::EventHandler::GetFrameForHandlingEventWith(
   return GetNearestFrameContainingPresShell(retargetPresShell);
 }
 
+bool PresShell::EventHandler::MaybeHandleEventWithAnotherPresShell(
+    nsIFrame* aFrameForPresShell, WidgetGUIEvent* aGUIEvent,
+    nsEventStatus* aEventStatus, nsresult* aRv) {
+  MOZ_ASSERT(aGUIEvent);
+  MOZ_ASSERT(aEventStatus);
+  MOZ_ASSERT(aRv);
+
+  *aRv = NS_OK;
+
+  RefPtr<Document> retargetEventDoc;
+  if (!GetRetargetEventDocument(aGUIEvent, getter_AddRefs(retargetEventDoc))) {
+    // Nobody can handle this event.  So, treat as handled by somebody to make
+    // caller do nothing anymore.
+    return true;
+  }
+
+  // If there is no proper retarget document, the caller should handle the
+  // event by itself.
+  if (!retargetEventDoc) {
+    return false;
+  }
+
+  nsIFrame* frame = GetFrameForHandlingEventWith(aGUIEvent, retargetEventDoc,
+                                                 aFrameForPresShell);
+  if (!frame) {
+    // Nobody can handle this event.  So, treat as handled by somebody to make
+    // caller do nothing anymore.
+    return true;
+  }
+
+  // If we reached same frame as set to HandleEvent(), the caller should handle
+  // the event by itself.
+  if (frame == aFrameForPresShell) {
+    return false;
+  }
+
+  // We need to handle aGUIEvent with another PresShell.
+  nsCOMPtr<nsIPresShell> shell = frame->PresContext()->GetPresShell();
+  *aRv = shell->HandleEvent(frame, aGUIEvent, true, aEventStatus);
+  return true;
+}
+
 Document* PresShell::GetPrimaryContentDocument() {
   nsPresContext* context = GetPresContext();
   if (!context || !context->IsRoot()) {

layout/base/PresShell.h

@@ -616,6 +616,28 @@ class PresShell final : public nsIPresShell,
                                            Document* aRetargetDocument,
                                            nsIFrame* aFrameForPresShell);
 
+    /**
+     * MaybeHandleEventWithAnotherPresShell() may handle aGUIEvent with another
+     * PresShell.
+     *
+     * @param aFrameForPresShell        Set aFrame of HandleEvent() which called
+     *                                  this method.
+     * @param aGUIEvent                 Handling event.
+     * @param aEventStatus              [in/out] EventStatus of aGUIEvent.
+     * @param aRv                       [out] Returns error if this gets an
+     *                                  error handling the event.
+     * @return                          false if caller needs to keep handling
+     *                                  the event by itself.
+     *                                  true if caller shouldn't keep handling
+     *                                  the event.  Note that when no PresShell
+     *                                  can handle the event, this returns true.
+     */
+    MOZ_CAN_RUN_SCRIPT
+    bool MaybeHandleEventWithAnotherPresShell(nsIFrame* aFrameForPresShell,
+                                              WidgetGUIEvent* aGUIEvent,
+                                              nsEventStatus* aEventStatus,
+                                              nsresult* aRv);
+
     MOZ_CAN_RUN_SCRIPT
     nsresult RetargetEventToParent(WidgetGUIEvent* aGUIEvent,
                                    nsEventStatus* aEventStatus);