QAbstractScrollArea: Don't include size of invisible scrollbars

Amend 3e59a88e8968c6cdac788926bec34c259146b6a8, which incorrectly used
isHidden() to test whether the scrollbar is visible or not.
QWidget::isHidden() is only true for child widgets that are explicitly
hidden (or created for visible parents, which the scrollbars are not).
Since the scrollbars are children of a container that is hidden and
shown, isHidden always returns false.

Instead, use QWidget::isVisibleTo, passing the scroll area, as that
tells us if the scrollbar's visibility is relevant for the layout of the
scroll area.

Add a test case for QAbstractScrollArea, verifying that the scrollbar's
size is correctly taken into account when calculating the size hint.
This change revealed an instability in the tests introduced in the
earlier commit: the layout process is asynchronous, requiring event
processing to update the visibility of the scrollbars. Add a call to
processEvents before storing the reference size hint. Also, explicitly
set a style that doesn't use transient scrollbars as otherwise we cannot
control when the scrollbars are shown.

The chagne also revealed an inaccuracy in the QListView test, which
only passed because the width of the vertical scrollbar was included.
We cannot use font metrics results to compare expected width, as the
item delegate's text rendering uses text layouts.

Task-number: QTBUG-69120
Fixes: QTBUG-109326
Fixes: QTBUG-113552
Pick-to: 6.6 6.5
Change-Id: I1f06f9e88046a77722291ac17c56090f8dff7cf3
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

1 files changed, 3 insertions, 2 deletions

diff --git a/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp b/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp
index cb6a05c135..2b908d4d4f 100644
--- a/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp
+++ b/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp
@@ -2564,8 +2564,9 @@ void tst_QListView::taskQTBUG_58749_adjustToContent()
     // use the long text and make sure the width is adjusted.
     model.setData(model.index(0, 0), longText);
     QApplication::processEvents();
-    QVERIFY(w.width() > longTextWidth);
-    QVERIFY(view->width() >= longTextWidth);
+    const QRect itemRect = view->visualRect(model.index(0, 0));
+    QVERIFY(w.width() > itemRect.width());
+    QCOMPARE_GE(view->width(), itemRect.width());
 }
 
 void tst_QListView::taskQTBUG_51086_skippingIndexesInSelectedIndexes()