QAbstractItemView: Make sure to update the editor geometries

QAbstractItemView::setIndexWidget() does not trigger a relayouting when
a new widget is set. This results in a wrong editor geometry under some
circumstances. Fix it by triggering a delayed relayout.

Fixes: QTBUG-81763
Change-Id: I75d0e19bd5e56d63effe4990d782d202fb39e3e6
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

src/widgets/itemviews/qabstractitemview.cpp

@@ -3234,8 +3234,10 @@ void QAbstractItemView::setIndexWidget(const QModelIndex &index, QWidget *widget
         widget->installEventFilter(this);
         widget->show();
         dataChanged(index, index); // update the geometry
-        if (!d->delayedPendingLayout)
+        if (!d->delayedPendingLayout) {
             widget->setGeometry(visualRect(index));
+            d->doDelayedItemsLayout();  // relayout due to updated geometry
+        }
     }
 }
 

tests/auto/widgets/itemviews/qtreeview/tst_qtreeview.cpp

@@ -952,6 +952,7 @@ void tst_QTreeView::indexWidget()
     QStandardItemModel treeModel;
     initStandardTreeModel(&treeModel);
     view.setModel(&treeModel);
+    view.resize(300, 400);  // make sure the width of the view is larger than the widgets below
 
     QModelIndex index = view.model()->index(0, 0);
 
@@ -980,6 +981,7 @@ void tst_QTreeView::indexWidget()
 
     //now let's try to do that later when the widget is already shown
     view.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&view));
     index = view.model()->index(1, 0);
     QVERIFY(!view.indexWidget(index));