Fix QTableView::doItemsLayout()

Keep the content aligned to the bottom when the view has been scrolled
to the bottom and the content is relayouted (for example due to
sorting).

Task-number: QTBUG-30653
(cherry-picked from qtbase commit 00b11ccdead05d77589d4ec5ebb3b376c6ae2ca1)
Change-Id: I183145fbd84339e82d2d1d0bc39cea33d9cc9734
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>

2 files changed, 42 insertions, 3 deletions

diff --git a/src/gui/itemviews/qtableview.cpp b/src/gui/itemviews/qtableview.cpp
index 13ce309a73..63036b2680 100644
--- a/src/gui/itemviews/qtableview.cpp
+++ b/src/gui/itemviews/qtableview.cpp
@@ -1108,10 +1108,15 @@ void QTableView::doItemsLayout()
 {
     Q_D(QTableView);
     QAbstractItemView::doItemsLayout();
-    if (verticalScrollMode() == QAbstractItemView::ScrollPerItem)
-        d->verticalHeader->setOffsetToSectionPosition(verticalScrollBar()->value());
-    else
+    if (verticalScrollMode() == QAbstractItemView::ScrollPerItem) {
+        const int max = verticalScrollBar()->maximum();
+        if (max > 0 && verticalScrollBar()->value() == max)
+            d->verticalHeader->setOffsetToLastSection();
+        else
+            d->verticalHeader->setOffsetToSectionPosition(verticalScrollBar()->value());
+    } else {
         d->verticalHeader->setOffset(verticalScrollBar()->value());
+    }
     if (!d->verticalHeader->updatesEnabled())
         d->verticalHeader->setUpdatesEnabled(true);
 }
diff --git a/tests/auto/qtableview/tst_qtableview.cpp b/tests/auto/qtableview/tst_qtableview.cpp
index 73cb3792a8..1939b61622 100644
--- a/tests/auto/qtableview/tst_qtableview.cpp
+++ b/tests/auto/qtableview/tst_qtableview.cpp
@@ -203,6 +203,7 @@ private slots:
     void taskQTBUG_7774_RtoLVisualRegionForSelection();
     void taskQTBUG_8777_scrollToSpans();
     void taskQTBUG_10169_sizeHintForRow();
+    void taskQTBUG_30653_doItemsLayout();
 
     void mouseWheel_data();
     void mouseWheel();
@@ -4069,5 +4070,38 @@ void tst_QTableView::taskQTBUG_10169_sizeHintForRow()
     QCOMPARE(orderedHeight, reorderedHeight);
 }
 
+void tst_QTableView::taskQTBUG_30653_doItemsLayout()
+{
+    QWidget topLevel;
+    QtTestTableView view(&topLevel);
+
+    QtTestTableModel model(5, 5);
+    view.setModel(&model);
+
+    QtTestItemDelegate delegate;
+    delegate.hint = QSize(50, 50);
+    view.setItemDelegate(&delegate);
+
+    view.resizeRowsToContents();
+    view.resizeColumnsToContents();
+
+    // show two and half rows/cols
+    int extraWidth = view.verticalHeader()->sizeHint().width() + view.verticalScrollBar()->sizeHint().width();
+    int extraHeight = view.horizontalHeader()->sizeHint().height() + view.horizontalScrollBar()->sizeHint().height();
+    view.resize(125 + extraWidth, 125 + extraHeight);
+
+    topLevel.show();
+    QVERIFY(QTest::qWaitForWindowShown(&topLevel));
+
+    // the offset after scrollToBottom() and doItemsLayout() should not differ
+    // as the view content should stay aligned to the last section
+    view.scrollToBottom();
+    int scrollToBottomOffset = view.verticalHeader()->offset();
+    view.doItemsLayout();
+    int doItemsLayoutOffset = view.verticalHeader()->offset();
+
+    QCOMPARE(scrollToBottomOffset, doItemsLayoutOffset);
+}
+
 QTEST_MAIN(tst_QTableView)
 #include "tst_qtableview.moc"