Fix QGraphicsView's abuse of QEvent's d-pointer in Leave event handling

QGraphicsSceneEvent carries a widget pointer, and we can add a new
event
type. Assert that QGraphicsScene doesn't get Leave events from
elsewhere.

This was the only "usage" of QEvent's d-pointer in Qt, so with this gone
we can reduce the size of QEvent by 8 bytes.

Change-Id: I0513daf742de9084d0469d55b7a7f41b667e8081
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 8 insertions, 2 deletions

diff --git a/src/widgets/graphicsview/qgraphicsscene.cpp b/src/widgets/graphicsview/qgraphicsscene.cpp
index 2f3cb4eaaf..2e65effb1a 100644
--- a/src/widgets/graphicsview/qgraphicsscene.cpp
+++ b/src/widgets/graphicsview/qgraphicsscene.cpp
@@ -3371,9 +3371,15 @@ bool QGraphicsScene::event(QEvent *event)
         break;
     }
     case QEvent::Leave:
-        // hackieshly unpacking the viewport pointer from the leave event.
-        d->leaveScene(reinterpret_cast<QWidget *>(event->d));
+        Q_ASSERT_X(false, "QGraphicsScene::event",
+                   "QGraphicsScene must not receive QEvent::Leave, use GraphicsSceneLeave");
         break;
+    case QEvent::GraphicsSceneLeave:
+    {
+        auto *leaveEvent = static_cast<QGraphicsSceneEvent*>(event);
+        d->leaveScene(leaveEvent->widget());
+        break;
+    }
     case QEvent::GraphicsSceneHelp:
         helpEvent(static_cast<QGraphicsSceneHelpEvent *>(event));
         break;