From d925bfcc6930594abfba44125c0d94b34f9c23f6 Mon Sep 17 00:00:00 2001
From: "Matt A. Tobin" <email@mattatobin.com>
Date: Fri, 17 Apr 2020 07:33:51 -0400
Subject: Bug 1327185 - Refine EventStateManager::FireDragEnterOrExit

Tag #1375
---
 dom/events/EventStateManager.cpp | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/dom/events/EventStateManager.cpp b/dom/events/EventStateManager.cpp
index e16d68c81..459521b83 100644
--- a/dom/events/EventStateManager.cpp
+++ b/dom/events/EventStateManager.cpp
@@ -3484,6 +3484,12 @@ EventStateManager::PostHandleEvent(nsPresContext* aPresContext,
      // make sure to fire the enter and exit_synth events after the
      // eDragExit event, otherwise we'll clean up too early
     GenerateDragDropEnterExit(presContext, aEvent->AsDragEvent());
+    if (ContentChild* child = ContentChild::GetSingleton()) {
+      // SendUpdateDropEffect to prevent nsIDragService from waiting for
+      // response of forwarded dragexit event.
+      child->SendUpdateDropEffect(nsIDragService::DRAGDROP_ACTION_NONE,
+                                  nsIDragService::DRAGDROP_ACTION_NONE);
+    }
     break;
 
   case eBeforeKeyUp:
@@ -4446,6 +4452,19 @@ EventStateManager::GenerateDragDropEnterExit(nsPresContext* aPresContext,
           FireDragEnterOrExit(sLastDragOverFrame->PresContext(),
                               aDragEvent, eDragExit,
                               targetContent, lastContent, sLastDragOverFrame);
+          nsIContent* target = sLastDragOverFrame ? sLastDragOverFrame.GetFrame()->GetContent() : nullptr;
+          if (IsRemoteTarget(target)) {
+            // Dragging something and moving from web content to chrome only
+            // fires dragexit and dragleave to xul:browser. We have to forward
+            // dragexit to sLastDragOverFrame when its content is a remote
+            // target. We don't forward dragleave since it's generated from
+            // dragexit.
+            WidgetDragEvent remoteEvent(aDragEvent->IsTrusted(), eDragExit,
+                                        aDragEvent->mWidget);
+            remoteEvent.AssignDragEventData(*aDragEvent, true);
+            nsEventStatus remoteStatus = nsEventStatus_eIgnore;
+            HandleCrossProcessEvent(&remoteEvent, &remoteStatus);
+          }
         }
 
         FireDragEnterOrExit(aPresContext, aDragEvent, eDragEnter,
@@ -4502,14 +4521,11 @@ EventStateManager::FireDragEnterOrExit(nsPresContext* aPresContext,
                                        nsIContent* aTargetContent,
                                        nsWeakFrame& aTargetFrame)
 {
+  MOZ_ASSERT(aMessage == eDragLeave || aMessage == eDragExit ||
+             aMessage == eDragEnter);
   nsEventStatus status = nsEventStatus_eIgnore;
   WidgetDragEvent event(aDragEvent->IsTrusted(), aMessage, aDragEvent->mWidget);
-  event.mRefPoint = aDragEvent->mRefPoint;
-  event.mModifiers = aDragEvent->mModifiers;
-  event.buttons = aDragEvent->buttons;
-  event.relatedTarget = aRelatedTarget;
-  event.inputSource = aDragEvent->inputSource;
-
+  event.AssignDragEventData(*aDragEvent, true);
   mCurrentTargetContent = aTargetContent;
 
   if (aTargetContent != aRelatedTarget) {
@@ -4527,10 +4543,7 @@ EventStateManager::FireDragEnterOrExit(nsPresContext* aPresContext,
 
     // collect any changes to moz cursor settings stored in the event's
     // data transfer.
-    if (aMessage == eDragLeave || aMessage == eDragExit ||
-        aMessage == eDragEnter) {
-      UpdateDragDataTransfer(&event);
-    }
+    UpdateDragDataTransfer(&event);
   }
 
   // Finally dispatch the event to the frame
-- 
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