From 1082038bd89d0bbba4df0d9b3f8af3cd0a2f96f2 Mon Sep 17 00:00:00 2001
From: Christian Ehrlicher <ch.ehrlicher@gmx.de>
Date: Wed, 22 Nov 2023 19:24:42 +0100
Subject: [PATCH] QTabBar: properly calc tab positions when changing tab
 position

When changing the tab position, the scroll offset is calculated wrongly
because the calculation is done before the size of the tabbar is
recalculated. Therefore wait until QTabBar gets the resize event and
calculate the new tab positions there.

Pick-to: 6.6 6.5
Fixes: QTBUG-119366
Change-Id: I261a91bb584409b9b0dac4339a32894f47540bcf
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
---
 src/widgets/widgets/qtabbar.cpp               |  9 +---
 .../widgets/widgets/qtabbar/tst_qtabbar.cpp   | 41 +++++++++++++++++++
 2 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/src/widgets/widgets/qtabbar.cpp b/src/widgets/widgets/qtabbar.cpp
index 91be20a5dc..e8e70dc61e 100644
--- a/src/widgets/widgets/qtabbar.cpp
+++ b/src/widgets/widgets/qtabbar.cpp
@@ -831,14 +831,9 @@ void QTabBarPrivate::refresh()
             pressedIndex = -1;
     }
 
-    if (!q->isVisible()) {
-        layoutDirty = true;
-    } else {
-        layoutTabs();
-        makeVisible(currentIndex);
+    layoutDirty = true;
+    if (q->isVisible())
         q->update();
-        q->updateGeometry();
-    }
 }
 
 /*!
diff --git a/tests/auto/widgets/widgets/qtabbar/tst_qtabbar.cpp b/tests/auto/widgets/widgets/qtabbar/tst_qtabbar.cpp
index 7aede22441..2e6ae0c4cd 100644
--- a/tests/auto/widgets/widgets/qtabbar/tst_qtabbar.cpp
+++ b/tests/auto/widgets/widgets/qtabbar/tst_qtabbar.cpp
@@ -101,6 +101,7 @@ private slots:
     void resizeKeepsScroll();
     void changeTabTextKeepsScroll();
     void settingCurrentTabBeforeShowDoesntScroll();
+    void checkPositionsAfterShapeChange();
 
 private:
     void checkPositions(const TabBar &tabbar, const QList<int> &positions);
@@ -1502,5 +1503,45 @@ void tst_QTabBar::settingCurrentTabBeforeShowDoesntScroll()
     QCOMPARE_GT(getScrollOffset(), 0);
 }
 
+void tst_QTabBar::checkPositionsAfterShapeChange()
+{
+    class TabWidget : public QTabWidget
+    {
+    public:
+        using QTabWidget::QTabWidget;
+        using QTabWidget::setTabBar;
+    };
+  
+    class TabBar : public QTabBar
+    {
+    public:
+        using QTabBar::initStyleOption;
+        void resizeEvent(QResizeEvent *e) override
+        {
+            QTabBar::resizeEvent(e);
+            resized = true;
+        }
+        bool resized = false;
+    };
+
+    TabWidget tabWidget;
+    auto *tabBar = new TabBar;
+    tabWidget.setTabBar(tabBar);
+    for (int i = 0; i < 3; ++i)
+        tabWidget.addTab(new QWidget, u"Tab %1"_s.arg(i));
+    tabWidget.setTabPosition(QTabWidget::North);
+    tabWidget.setCurrentIndex(2);
+    tabWidget.resize(300, 300);
+    tabWidget.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&tabWidget));
+
+    tabBar->resized = false;
+    tabWidget.setTabPosition(QTabWidget::East);
+    QVERIFY(QTest::qWaitFor([&]() { return tabBar->resized; }));
+    QStyleOptionTab opt;
+    tabBar->initStyleOption(&opt, 2);
+    QVERIFY(opt.rect.top() > 0);
+}
+
 QTEST_MAIN(tst_QTabBar)
 #include "tst_qtabbar.moc"