QTabBar: update index of last visible tab in insertTab

Index of the last visible tab was not updated, if a new tab was inserted
after the current tab and before the last tab.

When the new tab is inserted before the last visible tab, the index of
the last tab increments by one.
When the new tab is inserted after the last visible tab, then the newly
inserted tab becomes the last visible.

Fixes: QTBUG-86898
Change-Id: I2f4b7f705261ec35a5aa7b883ecdddba25f007b7
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

2 files changed, 31 insertions, 3 deletions

diff --git a/src/widgets/widgets/qtabbar.cpp b/src/widgets/widgets/qtabbar.cpp
index ab4478a98b..2c65240434 100644
--- a/src/widgets/widgets/qtabbar.cpp
+++ b/src/widgets/widgets/qtabbar.cpp
@@ -990,14 +990,16 @@ int QTabBar::insertTab(int index, const QIcon& icon, const QString &text)
     d->tabList.at(index)->shortcutId = grabShortcut(QKeySequence::mnemonic(text));
 #endif
     d->firstVisible = qMax(qMin(index, d->firstVisible), 0);
-    d->lastVisible  = qMax(index, d->lastVisible);
     d->refresh();
     if (d->tabList.count() == 1)
         setCurrentIndex(index);
-    else if (index <= d->currentIndex) {
+    else if (index <= d->currentIndex)
         ++d->currentIndex;
+
+    if (index <= d->lastVisible)
         ++d->lastVisible;
-    }
+    else
+        d->lastVisible = index;
 
     if (d->closeButtonOnTabs) {
         QStyleOptionTab opt;
diff --git a/tests/auto/widgets/widgets/qtabbar/tst_qtabbar.cpp b/tests/auto/widgets/widgets/qtabbar/tst_qtabbar.cpp
index db94e03ff4..d61b48a41c 100644
--- a/tests/auto/widgets/widgets/qtabbar/tst_qtabbar.cpp
+++ b/tests/auto/widgets/widgets/qtabbar/tst_qtabbar.cpp
@@ -59,6 +59,7 @@ private slots:
     void testCurrentChanged();
 
     void insertAtCurrentIndex();
+    void insertAfterCurrentIndex();
 
     void removeTab_data();
     void removeTab();
@@ -236,6 +237,31 @@ void tst_QTabBar::insertAtCurrentIndex()
     QCOMPARE(tabBar.currentIndex(), 3);
 }
 
+void tst_QTabBar::insertAfterCurrentIndex()
+{
+    TabBar tabBar;
+
+    tabBar.addTab("Tab10");
+    checkPositions(tabBar, { QStyleOptionTab::OnlyOneTab });
+
+    tabBar.addTab("Tab20");
+    checkPositions(tabBar, { QStyleOptionTab::Beginning, QStyleOptionTab::End });
+
+    tabBar.insertTab(1, "Tab15");
+    checkPositions(tabBar,
+                   { QStyleOptionTab::Beginning, QStyleOptionTab::Middle, QStyleOptionTab::End });
+
+    tabBar.insertTab(3, "Tab30");
+    checkPositions(tabBar,
+                   { QStyleOptionTab::Beginning, QStyleOptionTab::Middle, QStyleOptionTab::Middle,
+                     QStyleOptionTab::End });
+
+    tabBar.insertTab(3, "Tab25");
+    checkPositions(tabBar,
+                   { QStyleOptionTab::Beginning, QStyleOptionTab::Middle, QStyleOptionTab::Middle,
+                     QStyleOptionTab::Middle, QStyleOptionTab::End });
+}
+
 void tst_QTabBar::removeTab_data()
 {
     QTest::addColumn<int>("currentIndex");