QHeaderView::paintSection(): fix visible index handling

Sections may be hidden => QStyleOptionHeader::position must reflect the
state seen on the screen. Otherwise styles will give wrong visual
results.

Task-number: QTBUG-32203
Change-Id: I7ef86496be092bf6f52ec45f757b501f38c3a431
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>

3 files changed, 88 insertions, 3 deletions

diff --git a/src/widgets/itemviews/qheaderview.cpp b/src/widgets/itemviews/qheaderview.cpp
index edfbc5c8f1..864a55d2ea 100644
--- a/src/widgets/itemviews/qheaderview.cpp
+++ b/src/widgets/itemviews/qheaderview.cpp
@@ -2635,11 +2635,13 @@ void QHeaderView::paintSection(QPainter *painter, const QRect &rect, int logical
     // the section position
     int visual = visualIndex(logicalIndex);
     Q_ASSERT(visual != -1);
-    if (count() == 1)
+    bool first = d->isFirstVisibleSection(visual);
+    bool last = d->isLastVisibleSection(visual);
+    if (first && last)
         opt.position = QStyleOptionHeader::OnlyOneSection;
-    else if (visual == 0)
+    else if (first)
         opt.position = QStyleOptionHeader::Beginning;
-    else if (visual == count() - 1)
+    else if (last)
         opt.position = QStyleOptionHeader::End;
     else
         opt.position = QStyleOptionHeader::Middle;
@@ -3062,6 +3064,22 @@ bool QHeaderViewPrivate::isSectionSelected(int section) const
     return s;
 }
 
+bool QHeaderViewPrivate::isFirstVisibleSection(int section) const
+{
+    if (sectionStartposRecalc)
+        recalcSectionStartPos();
+    const SectionItem &item = sectionItems.at(section);
+    return item.size > 0 && item.calculated_startpos == 0;
+}
+
+bool QHeaderViewPrivate::isLastVisibleSection(int section) const
+{
+    if (sectionStartposRecalc)
+        recalcSectionStartPos();
+    const SectionItem &item = sectionItems.at(section);
+    return item.size > 0 && item.calculatedEndPos() == length;
+}
+
 /*!
     \internal
     Returns the last visible (ie. not hidden) visual index
diff --git a/src/widgets/itemviews/qheaderview_p.h b/src/widgets/itemviews/qheaderview_p.h
index 7fda0c8873..f886430ba8 100644
--- a/src/widgets/itemviews/qheaderview_p.h
+++ b/src/widgets/itemviews/qheaderview_p.h
@@ -114,6 +114,8 @@ public:
     void _q_layoutChanged();
 
     bool isSectionSelected(int section) const;
+    bool isFirstVisibleSection(int section) const;
+    bool isLastVisibleSection(int section) const;
 
     inline bool rowIntersectsSelection(int row) const {
         return (selectionModel ? selectionModel->rowIntersectsSelection(row, root) : false);
diff --git a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
index fa67e16db9..548b74f914 100644
--- a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
+++ b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
@@ -46,6 +46,7 @@
 #include <QStringListModel>
 #include <QSortFilterProxyModel>
 #include <QTableView>
+#include <QProxyStyle>
 
 #include <qabstractitemmodel.h>
 #include <qapplication.h>
@@ -59,6 +60,20 @@ typedef QList<int> IntList;
 
 typedef QList<bool> BoolList;
 
+class TestStyle : public QProxyStyle
+{
+public:
+    void drawControl(ControlElement element, const QStyleOption *option, QPainter *painter, const QWidget *widget) const
+    {
+        if (element == CE_HeaderSection) {
+            if (const QStyleOptionHeader *header = qstyleoption_cast<const QStyleOptionHeader *>(option))
+                lastPosition = header->position;
+        }
+        QProxyStyle::drawControl(element, option, painter, widget);
+    }
+    mutable QStyleOptionHeader::SectionPosition lastPosition;
+};
+
 class protected_QHeaderView : public QHeaderView
 {
     Q_OBJECT
@@ -229,6 +244,7 @@ private slots:
     void mixedTests();
     void resizeToContentTest();
     void testStreamWithHide();
+    void testStylePosition();
 
 protected:
     void setupTestData(bool use_reset_model = false);
@@ -2732,5 +2748,54 @@ void tst_QHeaderView::testStreamWithHide()
 #endif
 }
 
+void tst_QHeaderView::testStylePosition()
+{
+    topLevel->show();
+    QVERIFY(QTest::qWaitForWindowExposed(topLevel));
+
+    protected_QHeaderView *header = static_cast<protected_QHeaderView *>(view);
+
+    TestStyle proxy;
+    header->setStyle(&proxy);
+
+    QImage image(1, 1, QImage::Format_ARGB32);
+    QPainter p(&image);
+
+    // 0, 1, 2, 3
+    header->paintSection(&p, view->rect(), 0);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::Beginning);
+    header->paintSection(&p, view->rect(), 1);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::Middle);
+    header->paintSection(&p, view->rect(), 2);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::Middle);
+    header->paintSection(&p, view->rect(), 3);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::End);
+
+    // (0),2,1,3
+    view->setSectionHidden(0, true);
+    view->swapSections(1, 2);
+    header->paintSection(&p, view->rect(), 1);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::Middle);
+    header->paintSection(&p, view->rect(), 2);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::Beginning);
+    header->paintSection(&p, view->rect(), 3);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::End);
+
+    // (1),2,0,(3)
+    view->setSectionHidden(3, true);
+    view->setSectionHidden(0, false);
+    view->setSectionHidden(1, true);
+    view->swapSections(0, 1);
+    header->paintSection(&p, view->rect(), 0);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::End);
+    header->paintSection(&p, view->rect(), 2);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::Beginning);
+
+    // (1),2,(0),(3)
+    view->setSectionHidden(0, true);
+    header->paintSection(&p, view->rect(), 2);
+    QCOMPARE(proxy.lastPosition, QStyleOptionHeader::OnlyOneSection);
+}
+
 QTEST_MAIN(tst_QHeaderView)
 #include "tst_qheaderview.moc"