QHeaderView: allow un-sorting of models

If one clicks on a QHeaderView's section, the header view will
sort the view by the respective column/row. By clicking multiple
times, one is able to toggle the sorting between ascending
and descending. Something that is NOT possible to do however is to
un-sort the view -- that is, to restore the model's original
sorting. This must be done via code, by asking the header or the
view to sort by section -1.

This commit adds new property to QHeaderView to make it possible
to unsort models. Basically, the sort indicator becomes a tri-state:
sort ascending, sort descending, unsort (sort by column -1).

[ChangeLog][QtWidgets][QHeaderView] Added the sortIndicatorClearable
property. Setting this property allows the user to clear the sort
indicator on a section, resetting the model to its default ordering.

Change-Id: Ibf4e280b2086b75ccd64d619ea4d70816dc3529f
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: David Faure <david.faure@kdab.com>

1 files changed, 70 insertions, 0 deletions

diff --git a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
index 83c6ed1c9f..610d99999a 100644
--- a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
+++ b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
@@ -156,6 +156,7 @@ private slots:
     void moveAndInsertSection();
     void highlightSections();
     void showSortIndicator();
+    void clearSectionSorting();
     void sortIndicatorTracking();
     void removeAndInsertRow();
     void unhideSection();
@@ -1333,6 +1334,75 @@ void tst_QHeaderView::showSortIndicator()
     // Don't assert baby :)
 }
 
+void tst_QHeaderView::clearSectionSorting()
+{
+    QStandardItemModel m(4, 4);
+    QHeaderView h(Qt::Horizontal);
+
+    QCOMPARE(h.sortIndicatorSection(), 0);
+    QCOMPARE(h.sortIndicatorOrder(), Qt::DescendingOrder);
+
+    h.setModel(&m);
+    h.setSectionsClickable(true);
+    h.setSortIndicatorShown(true);
+    h.setSortIndicator(-1, Qt::DescendingOrder);
+    h.show();
+
+    QVERIFY(QTest::qWaitForWindowExposed(&h));
+
+    QCOMPARE(h.sortIndicatorSection(), -1);
+    QCOMPARE(h.sortIndicatorOrder(), Qt::DescendingOrder);
+
+    QSignalSpy sectionClickedSpy(&h, &QHeaderView::sectionClicked);
+    QVERIFY(sectionClickedSpy.isValid());
+    QCOMPARE(sectionClickedSpy.count(), 0);
+
+    QSignalSpy sortIndicatorChangedSpy(&h, &QHeaderView::sortIndicatorChanged);
+    QVERIFY(sortIndicatorChangedSpy.isValid());
+    QCOMPARE(sortIndicatorChangedSpy.count(), 0);
+
+    enum { Count = 30 };
+
+    // normal behavior: clicking multiple times will just toggle the sort indicator
+    for (int i = 0; i < Count; ++i) {
+        QTest::mouseClick(h.viewport(), Qt::LeftButton, Qt::NoModifier, QPoint(5, 5));
+        QCOMPARE(sectionClickedSpy.count(), i + 1);
+        QCOMPARE(sortIndicatorChangedSpy.count(), i + 1);
+        QCOMPARE(h.sortIndicatorSection(), 0);
+        const auto expectedOrder = (i % 2) == 0 ? Qt::AscendingOrder : Qt::DescendingOrder;
+        QCOMPARE(h.sortIndicatorOrder(), expectedOrder);
+    }
+
+    h.setSortIndicator(-1, Qt::DescendingOrder);
+    h.setSortIndicatorClearable(true);
+    QCOMPARE(h.sortIndicatorSection(), -1);
+    QCOMPARE(h.sortIndicatorOrder(), Qt::DescendingOrder);
+
+    sectionClickedSpy.clear();
+    sortIndicatorChangedSpy.clear();
+
+    // clearing behavior: clicking multiple times will be tristate (asc, desc, nothing)
+    for (int i = 0; i < Count; ++i) {
+        QTest::mouseClick(h.viewport(), Qt::LeftButton, Qt::NoModifier, QPoint(5, 5));
+        QCOMPARE(sectionClickedSpy.count(), i + 1);
+        QCOMPARE(sortIndicatorChangedSpy.count(), i + 1);
+        switch (i % 3) {
+        case 0:
+            QCOMPARE(h.sortIndicatorSection(), 0);
+            QCOMPARE(h.sortIndicatorOrder(), Qt::AscendingOrder);
+            break;
+        case 1:
+            QCOMPARE(h.sortIndicatorSection(), 0);
+            QCOMPARE(h.sortIndicatorOrder(), Qt::DescendingOrder);
+            break;
+        case 2:
+            QCOMPARE(h.sortIndicatorSection(), -1);
+            QCOMPARE(h.sortIndicatorOrder(), Qt::AscendingOrder);
+            break;
+        }
+    }
+}
+
 void tst_QHeaderView::sortIndicatorTracking()
 {
     QtTestModel model(10, 10);