1 files changed, 16 insertions, 9 deletions

diff --git a/src/widgets/widgets/qtabbar.cpp b/src/widgets/widgets/qtabbar.cpp
index 4b649a70ac..9a382e96dd 100644
--- a/src/widgets/widgets/qtabbar.cpp
+++ b/src/widgets/widgets/qtabbar.cpp
@@ -407,10 +407,12 @@ void QTabBarPrivate::init()
 {
     Q_Q(QTabBar);
     leftB = new QToolButton(q);
+    leftB->setObjectName(QStringLiteral("ScrollLeftButton"));
     leftB->setAutoRepeat(true);
     QObject::connect(leftB, SIGNAL(clicked()), q, SLOT(_q_scrollTabs()));
     leftB->hide();
     rightB = new QToolButton(q);
+    rightB->setObjectName(QStringLiteral("ScrollRightButton"));
     rightB->setAutoRepeat(true);
     QObject::connect(rightB, SIGNAL(clicked()), q, SLOT(_q_scrollTabs()));
     rightB->hide();
@@ -831,21 +833,24 @@ void QTabBarPrivate::_q_scrollTabs()
     Q_Q(QTabBar);
     const QObject *sender = q->sender();
     const bool horizontal = !verticalTabs(shape);
-    const QRect scrollRect = normalizedScrollRect();
+    const QRect scrollRect = normalizedScrollRect().translated(scrollOffset, 0);
+
     int i = -1;
 
     if (sender == leftB) {
         for (i = tabList.count() - 1; i >= 0; --i) {
             int start = horizontal ? tabList.at(i).rect.left() : tabList.at(i).rect.top();
-            if (start < scrollRect.left() + scrollOffset) {
+            if (start < scrollRect.left()) {
                 makeVisible(i);
                 return;
             }
         }
     } else if (sender == rightB) {
         for (i = 0; i < tabList.count(); ++i) {
-            int end = horizontal ? tabList.at(i).rect.right() : tabList.at(i).rect.bottom();
-            if (end > scrollRect.right() + scrollOffset) {
+            const auto tabRect = tabList.at(i).rect;
+            int start = horizontal ? tabRect.left() : tabRect.top();
+            int end = horizontal ? tabRect.right() : tabRect.bottom();
+            if (end > scrollRect.right() && start > scrollOffset) {
                 makeVisible(i);
                 return;
             }
@@ -997,14 +1002,16 @@ int QTabBar::insertTab(int index, const QIcon& icon, const QString &text)
     d->tabList[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) {
         QStyleOptionTabV4 opt;
@@ -2397,7 +2404,7 @@ void QTabBar::timerEvent(QTimerEvent *event)
     This property controls how items are elided when there is not
     enough space to show them for a given tab bar size.
 
-    By default the value is style dependent.
+    By default the value is style-dependent.
 
     \sa QTabWidget::elideMode, usesScrollButtons, QStyle::SH_TabBar_ElideMode
 */
@@ -2426,7 +2433,7 @@ void QTabBar::setElideMode(Qt::TextElideMode mode)
     When there are too many tabs in a tab bar for its size, the tab bar can either choose
     to expand its size or to add buttons that allow you to scroll through the tabs.
 
-    By default the value is style dependant.
+    By default the value is style-dependent.
 
     \sa elideMode, QTabWidget::usesScrollButtons, QStyle::SH_TabBar_PreferNoArrows
 */