Possible assert when hiding tabbed QDockWidget

The problem is in QTabBar which emits the currentChanged signal
before accessing its own internal data. As we react to that signal by
possibly removing/adding tabs, it can cause a assertion failure.

Task-number: 251184
Reviewed-by: ogoffart

2 files changed, 35 insertions, 3 deletions

diff --git a/src/gui/widgets/qtabbar.cpp b/src/gui/widgets/qtabbar.cpp
index b6e6b6d..b562b1f 100644
--- a/src/gui/widgets/qtabbar.cpp
+++ b/src/gui/widgets/qtabbar.cpp
@@ -1167,13 +1167,13 @@ void QTabBar::setCurrentIndex(int index)
         d->currentIndex = index;
         update();
         d->makeVisible(index);
+        d->tabList[index].lastTab = oldIndex;
+        d->layoutWidgets(oldIndex);
+        d->layoutWidgets(index);
 #ifdef QT3_SUPPORT
         emit selected(index);
 #endif
         emit currentChanged(index);
-        d->tabList[index].lastTab = oldIndex;
-        d->layoutWidgets(oldIndex);
-        d->layoutWidgets(index);
     }
 }
 
diff --git a/tests/auto/qtabbar/tst_qtabbar.cpp b/tests/auto/qtabbar/tst_qtabbar.cpp
index 433eb86..31722de 100644
--- a/tests/auto/qtabbar/tst_qtabbar.cpp
+++ b/tests/auto/qtabbar/tst_qtabbar.cpp
@@ -92,6 +92,8 @@ private slots:
 
     void moveTab_data();
     void moveTab();
+
+    void task251184_removeTab();
 };
 
 // Testing get/set functions
@@ -503,5 +505,35 @@ void tst_QTabBar::moveTab()
     bar.callMoveTab(from, to);
 }
 
+
+class MyTabBar : public QTabBar
+{
+    Q_OBJECT
+public slots:
+    void onCurrentChanged()
+    {
+        //we just want this to be done once
+        disconnect(this, SIGNAL(currentChanged(int)), this, SLOT(onCurrentChanged()));
+        removeTab(0);
+    }
+};
+
+void tst_QTabBar::task251184_removeTab()
+{
+    MyTabBar bar;
+    bar.addTab("bar1");
+    bar.addTab("bar2");
+    QCOMPARE(bar.count(), 2);
+    QCOMPARE(bar.currentIndex(), 0);
+
+    bar.connect(&bar, SIGNAL(currentChanged(int)), SLOT(onCurrentChanged()));
+    bar.setCurrentIndex(1);
+
+    QCOMPARE(bar.count(), 1);
+    QCOMPARE(bar.currentIndex(), 0);
+    QCOMPARE(bar.tabText(bar.currentIndex()), QString("bar2"));    
+}
+
+
 QTEST_MAIN(tst_QTabBar)
 #include "tst_qtabbar.moc"