Bug 1653949 - Part 1: Change mExitFrom in WidgetMouseEvent to be Maybe<ExitFrom>; r=smaug

mExitFrom now contains a value only when mMessage is eMouseExitFromWidget

Differential Revision: https://phabricator.services.mozilla.com/D88225

dom/base/nsContentUtils.cpp

@@ -7820,7 +7820,7 @@ nsresult nsContentUtils::SendMouseEvent(
   if (!widget) return NS_ERROR_FAILURE;
 
   EventMessage msg;
-  WidgetMouseEvent::ExitFrom exitFrom = WidgetMouseEvent::eChild;
+  Maybe<WidgetMouseEvent::ExitFrom> exitFrom;
   bool contextMenuKey = false;
   if (aType.EqualsLiteral("mousedown")) {
     msg = eMouseDown;
@@ -7832,9 +7832,10 @@ nsresult nsContentUtils::SendMouseEvent(
     msg = eMouseEnterIntoWidget;
   } else if (aType.EqualsLiteral("mouseout")) {
     msg = eMouseExitFromWidget;
+    exitFrom = Some(WidgetMouseEvent::eChild);
   } else if (aType.EqualsLiteral("mousecancel")) {
     msg = eMouseExitFromWidget;
-    exitFrom = WidgetMouseEvent::eTopLevel;
+    exitFrom = Some(WidgetMouseEvent::eTopLevel);
   } else if (aType.EqualsLiteral("mouselongtap")) {
     msg = eMouseLongTap;
   } else if (aType.EqualsLiteral("contextmenu")) {

dom/events/EventStateManager.cpp

@@ -649,7 +649,7 @@ nsresult EventStateManager::PreHandleEvent(nsPresContext* aPresContext,
       // If the event is not a top-level window exit, then it's not
       // really an exit --- we may have traversed widget boundaries but
       // we're still in our toplevel window.
-      if (mouseEvent->mExitFrom != WidgetMouseEvent::eTopLevel) {
+      if (mouseEvent->mExitFrom.value() != WidgetMouseEvent::eTopLevel) {
         // Treat it as a synthetic move so we don't generate spurious
         // "exit" or "move" events.  Any necessary "out" or "over" events
         // will be generated by GenerateMouseEnterExit
@@ -1327,6 +1327,7 @@ void EventStateManager::DispatchCrossProcessEvent(WidgetEvent* aEvent,
           UniquePtr<WidgetMouseEvent> mouseExitEvent =
               CreateMouseOrPointerWidgetEvent(mouseEvent, eMouseExitFromWidget,
                                               mouseEvent->mRelatedTarget);
+          mouseExitEvent->mExitFrom = Some(WidgetMouseEvent::eChild);
           oldRemote->SendRealMouseEvent(*mouseExitEvent);
         }
 
@@ -4223,7 +4224,7 @@ nsIFrame* EventStateManager::DispatchMouseOrPointerEvent(
         UniquePtr<WidgetMouseEvent> remoteEvent =
             CreateMouseOrPointerWidgetEvent(aMouseEvent, eMouseExitFromWidget,
                                             relatedContent);
-        remoteEvent->mExitFrom = WidgetMouseEvent::eTopLevel;
+        remoteEvent->mExitFrom = Some(WidgetMouseEvent::eTopLevel);
 
         // mCurrentTarget is set to the new target, so we must reset it to the
         // old target and then dispatch a cross-process event. (mCurrentTarget

layout/base/PresShell.cpp

@@ -6984,9 +6984,9 @@ nsresult PresShell::EventHandler::HandleEventUsingCoordinates(
   }
 
   WidgetMouseEvent* mouseEvent = aGUIEvent->AsMouseEvent();
-  bool isWindowLevelMouseExit =
-      (aGUIEvent->mMessage == eMouseExitFromWidget) &&
-      (mouseEvent && mouseEvent->mExitFrom == WidgetMouseEvent::eTopLevel);
+  bool isWindowLevelMouseExit = (aGUIEvent->mMessage == eMouseExitFromWidget) &&
+                                (mouseEvent && mouseEvent->mExitFrom.value() ==
+                                                   WidgetMouseEvent::eTopLevel);
 
   // Get the frame at the event point. However, don't do this if we're
   // capturing and retargeting the event because the captured frame will

widget/MouseEvents.h

@@ -197,7 +197,6 @@ class WidgetMouseEvent : public WidgetMouseEventBase,
   WidgetMouseEvent()
       : mReason(eReal),
         mContextMenuTrigger(eNormal),
-        mExitFrom(eChild),
         mIgnoreRootScrollFrame(false),
         mClickCount(0),
         mUseLegacyNonPrimaryDispatch(false) {}
@@ -207,7 +206,6 @@ class WidgetMouseEvent : public WidgetMouseEventBase,
       : WidgetMouseEventBase(aIsTrusted, aMessage, aWidget, aEventClassID),
         mReason(aReason),
         mContextMenuTrigger(eNormal),
-        mExitFrom(eChild),
         mIgnoreRootScrollFrame(false),
         mClickCount(0),
         mUseLegacyNonPrimaryDispatch(false) {}
@@ -221,7 +219,6 @@ class WidgetMouseEvent : public WidgetMouseEventBase,
       : WidgetMouseEventBase(aIsTrusted, aMessage, aWidget, eMouseEventClass),
         mReason(aReason),
         mContextMenuTrigger(aContextMenuTrigger),
-        mExitFrom(eChild),
         mIgnoreRootScrollFrame(false),
         mClickCount(0),
         mUseLegacyNonPrimaryDispatch(false) {
@@ -269,10 +266,10 @@ class WidgetMouseEvent : public WidgetMouseEventBase,
   // other reasons (typically, a click of right mouse button).
   ContextMenuTrigger mContextMenuTrigger;
 
-  // mExitFrom is valid only when mMessage is eMouseExitFromWidget.
+  // mExitFrom contains a value only when mMessage is eMouseExitFromWidget.
   // This indicates if the mouse cursor exits from a top level widget or
   // a child widget.
-  ExitFrom mExitFrom;
+  Maybe<ExitFrom> mExitFrom;
 
   // Whether the event should ignore scroll frame bounds during dispatch.
   bool mIgnoreRootScrollFrame;

widget/cocoa/nsChildView.mm

@@ -3159,9 +3159,9 @@ NSEvent* gLastDragMouseDownEvent = nil;  // [strong]
   EventMessage msg = aEnter ? eMouseEnterIntoWidget : eMouseExitFromWidget;
   WidgetMouseEvent event(true, msg, mGeckoChild, WidgetMouseEvent::eReal);
   event.mRefPoint = mGeckoChild->CocoaPointsToDevPixels(localEventLocation);
-
-  event.mExitFrom = aExitFrom;
-
+  if (event.mMessage == eMouseExitFromWidget) {
+    event.mExitFrom = Some(aExitFrom);
+  }
   nsEventStatus status;  // ignored
   mGeckoChild->DispatchEvent(&event, status);
 }

widget/gtk/nsWindow.cpp

@@ -3199,9 +3199,9 @@ void nsWindow::OnLeaveNotifyEvent(GdkEventCrossing* aEvent) {
   event.mRefPoint = GdkEventCoordsToDevicePixels(aEvent->x, aEvent->y);
   event.AssignEventTime(GetWidgetEventTime(aEvent->time));
 
-  event.mExitFrom = is_top_level_mouse_exit(mGdkWindow, aEvent)
-                        ? WidgetMouseEvent::eTopLevel
-                        : WidgetMouseEvent::eChild;
+  event.mExitFrom = Some(is_top_level_mouse_exit(mGdkWindow, aEvent)
+                             ? WidgetMouseEvent::eTopLevel
+                             : WidgetMouseEvent::eChild);
 
   LOG(("OnLeaveNotify: %p\n", (void*)this));
 

widget/nsGUIEventIPC.h

@@ -244,7 +244,11 @@ struct ParamTraits<mozilla::WidgetMouseEvent> {
     WriteParam(aMsg, static_cast<paramType::ReasonType>(aParam.mReason));
     WriteParam(aMsg, static_cast<paramType::ContextMenuTriggerType>(
                          aParam.mContextMenuTrigger));
-    WriteParam(aMsg, static_cast<paramType::ExitFromType>(aParam.mExitFrom));
+    WriteParam(aMsg, aParam.mExitFrom.isSome());
+    if (aParam.mExitFrom.isSome()) {
+      WriteParam(
+          aMsg, static_cast<paramType::ExitFromType>(aParam.mExitFrom.value()));
+    }
     WriteParam(aMsg, aParam.mClickCount);
   }
 
@@ -253,20 +257,24 @@ struct ParamTraits<mozilla::WidgetMouseEvent> {
     bool rv;
     paramType::ReasonType reason = 0;
     paramType::ContextMenuTriggerType contextMenuTrigger = 0;
-    paramType::ExitFromType exitFrom = 0;
+    bool hasExitFrom = false;
     rv = ReadParam(aMsg, aIter,
                    static_cast<mozilla::WidgetMouseEventBase*>(aResult)) &&
          ReadParam(aMsg, aIter,
                    static_cast<mozilla::WidgetPointerHelper*>(aResult)) &&
          ReadParam(aMsg, aIter, &aResult->mIgnoreRootScrollFrame) &&
          ReadParam(aMsg, aIter, &reason) &&
-         ReadParam(aMsg, aIter, &contextMenuTrigger) &&
-         ReadParam(aMsg, aIter, &exitFrom) &&
-         ReadParam(aMsg, aIter, &aResult->mClickCount);
+         ReadParam(aMsg, aIter, &contextMenuTrigger);
     aResult->mReason = static_cast<paramType::Reason>(reason);
     aResult->mContextMenuTrigger =
         static_cast<paramType::ContextMenuTrigger>(contextMenuTrigger);
-    aResult->mExitFrom = static_cast<paramType::ExitFrom>(exitFrom);
+    rv = rv && ReadParam(aMsg, aIter, &hasExitFrom);
+    if (hasExitFrom) {
+      paramType::ExitFromType exitFrom = 0;
+      rv = rv && ReadParam(aMsg, aIter, &exitFrom);
+      aResult->mExitFrom = Some(static_cast<paramType::ExitFrom>(exitFrom));
+    }
+    rv = rv && ReadParam(aMsg, aIter, &aResult->mClickCount);
     return rv;
   }
 };

widget/windows/nsWindow.cpp

@@ -4555,8 +4555,9 @@ bool nsWindow::DispatchMouseEvent(EventMessage aEventMessage, WPARAM wParam,
       }
       break;
     case eMouseExitFromWidget:
-      event.mExitFrom = IsTopLevelMouseExit(mWnd) ? WidgetMouseEvent::eTopLevel
-                                                  : WidgetMouseEvent::eChild;
+      event.mExitFrom =
+          Some(IsTopLevelMouseExit(mWnd) ? WidgetMouseEvent::eTopLevel
+                                         : WidgetMouseEvent::eChild);
       break;
     default:
       break;