QHeaderView: Preserve settings on layoutChange with empty model

Do not clear the settings of QHeaderView during layoutChange when the
model is empty and the section count did not change. This will not work
when a section is moved or a section is replaced with a new one during
layoutChange. But since layoutChanged is also called on sorting, this
patch ensures that the settings are not cleared in this case.
This restores the behavior to the same as before 5.9.4.

Task-number: QTBUG-66444
Task-number: QTBUG-65478
Change-Id: I39989cfd45b42e58f49d18ec014d3a941cadb6c9
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
index c69c0de949..97aa8a0299 100644
--- a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
+++ b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
@@ -206,6 +206,7 @@ private slots:
     void task248050_hideRow();
     void QTBUG6058_reset();
     void QTBUG7833_sectionClicked();
+    void checkLayoutChangeEmptyModel();
     void QTBUG8650_crashOnInsertSections();
     void QTBUG12268_hiddenMovedSectionSorting();
     void QTBUG14242_hideSectionAutoSize();
@@ -286,6 +287,13 @@ public:
         endInsertColumns();
     }
 
+    void removeFirstRow()
+    {
+        beginRemoveRows(QModelIndex(), 0, 0);
+        --rows;
+        endRemoveRows();
+    }
+
     void removeLastRow()
     {
         beginRemoveRows(QModelIndex(), rows - 1, rows - 1);
@@ -328,6 +336,24 @@ public:
         emit layoutChanged();
     }
 
+    void emitLayoutChanged()
+    {
+        emit layoutAboutToBeChanged();
+        emit layoutChanged();
+    }
+
+    void emitLayoutChangedWithRemoveFirstRow()
+    {
+        emit layoutAboutToBeChanged();
+        QModelIndexList milNew;
+        const auto milOld = persistentIndexList();
+        milNew.reserve(milOld.size());
+        for (int i = 0; i < milOld.size(); ++i)
+            milNew += QModelIndex();
+        changePersistentIndexList(milOld, milNew);
+        emit layoutChanged();
+    }
+
     int cols, rows;
     mutable bool wrongIndex;
 };
@@ -2332,6 +2358,51 @@ void tst_QHeaderView::QTBUG7833_sectionClicked()
     QCOMPARE(pressedSpy.at(2).at(0).toInt(), 0);
 }
 
+void tst_QHeaderView::checkLayoutChangeEmptyModel()
+{
+    QtTestModel tm;
+    tm.cols = 11;
+    QTableView tv;
+    tv.setModel(&tm);
+
+    const int section4Size = tv.horizontalHeader()->sectionSize(4) + 1;
+    const int section5Size = section4Size + 1;
+    tv.horizontalHeader()->resizeSection(4, section4Size);
+    tv.horizontalHeader()->resizeSection(5, section5Size);
+    tv.setColumnHidden(5, true);
+    tv.setColumnHidden(6, true);
+    tv.horizontalHeader()->swapSections(8, 10);
+
+    tv.sortByColumn(1, Qt::AscendingOrder);
+    tm.emitLayoutChanged();
+
+    QCOMPARE(tv.isColumnHidden(5), true);
+    QCOMPARE(tv.isColumnHidden(6), true);
+    QCOMPARE(tv.horizontalHeader()->sectionsMoved(), true);
+    QCOMPARE(tv.horizontalHeader()->logicalIndex(8), 10);
+    QCOMPARE(tv.horizontalHeader()->logicalIndex(10), 8);
+    QCOMPARE(tv.horizontalHeader()->sectionSize(4), section4Size);
+    tv.setColumnHidden(5, false);   // unhide, section size must be properly restored
+    QCOMPARE(tv.horizontalHeader()->sectionSize(5), section5Size);
+    tv.setColumnHidden(5, true);
+
+    // adjust
+    tm.rows = 3;
+    tm.emitLayoutChanged();
+
+    // remove the row used for QPersistenModelIndexes
+    tm.emitLayoutChangedWithRemoveFirstRow();
+    QCOMPARE(tv.isColumnHidden(5), true);
+    QCOMPARE(tv.isColumnHidden(6), true);
+    QCOMPARE(tv.horizontalHeader()->sectionsMoved(), true);
+    QCOMPARE(tv.horizontalHeader()->logicalIndex(8), 10);
+    QCOMPARE(tv.horizontalHeader()->logicalIndex(10), 8);
+    QCOMPARE(tv.horizontalHeader()->sectionSize(4), section4Size);
+    tv.setColumnHidden(5, false);   // unhide, section size must be properly restored
+    QCOMPARE(tv.horizontalHeader()->sectionSize(5), section5Size);
+    tv.setColumnHidden(5, true);
+}
+
 void tst_QHeaderView::QTBUG8650_crashOnInsertSections()
 {
     QStringList headerLabels;