QGraphicsItem: Fix mouse tracking with modal panels

This fixes the case where a mouse tracking item is added to the scene while a modal panel is blocking. In order to optimize event delivery, mouse tracking is enabled for the view only when an item that needs it is added. This means that we cannot use itemAcceptsHoverEvents_helper(), since that returns whether the item _currently_ needs hover events, and we need to know whether it will need them in the future. [ChangeLog][QtWidgets][QGraphicsView] Fixed a bug where hover events would not be delivered if the item was added while blocked by a modal panel. Fixes: QTBUG-77233 Change-Id: Ifc95869f2cc9c8c048330928ef8a13cd27cfd0f9 Reviewed-by: Volker Hilsheimer <[email protected]> Reviewed-by: Andreas Aardal Hanssen <[email protected]>
HoBoIs · Dec 5, 2019 · 5a6fb46 · 5a6fb46
1 parent 913146c
commit 5a6fb46
Showing 1 changed file with 10 additions and 2 deletions.
diff --git a/src/widgets/graphicsview/qgraphicsscene.cpp b/src/widgets/graphicsview/qgraphicsscene.cpp
@@ -2568,8 +2568,16 @@ void QGraphicsScene::addItem(QGraphicsItem *item)
     ++d->selectionChanging;
     int oldSelectedItemSize = d->selectedItems.size();
 
-    // Enable mouse tracking if the item accepts hover events or has a cursor set.
-    if (d->allItemsIgnoreHoverEvents && d->itemAcceptsHoverEvents_helper(item)) {
+    // Enable mouse tracking if we haven't already done so, and the item needs it.
+    // We cannot use itemAcceptsHoverEvents_helper() here, since we need to enable
+    // mouse tracking also if this item is temporarily blocked by a modal panel.
+
+    auto needsMouseTracking = [](const QGraphicsItemPrivate *item) {
+        return item->acceptsHover
+                || (item->isWidget && static_cast<const QGraphicsWidgetPrivate *>(item)->hasDecoration());
+    };
+
+    if (d->allItemsIgnoreHoverEvents && needsMouseTracking(item->d_ptr.data())) {
         d->allItemsIgnoreHoverEvents = false;
         d->enableMouseTrackingOnViews();
     }