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Improve performance of QTabWidget::clear

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The current implementation of QTabWidget::clear is quite poor because it
deletes the tabs from first to last. When I was playing around, I found
out it's much faster to delete from last to first (with a lot of tabs it
goes from two seconds to 200 milliseconds in my testing). I assume this
has to do with the redrawing of all remaining tabs for each removeTab
call, while this is not necessary when removing in the reverse order.

Also, disable the stack widget's layout while we remove all tabs to
avoid unnecessary event posting, and disable updates of the stacked
widget as well as the tab bar.

Pick-to: 6.8
Change-Id: I04972de05ab71f98da7f74412aaadc69a36efc32
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
This commit is contained in:
Pieter Dewachter 2024-11-05 10:07:41 +01:00 committed by Volker Hilsheimer
parent 1393ece7c0
commit 8717c1752f
1 changed files with 14 additions and 3 deletions
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17
src/widgets/widgets/qtabwidget.cpp
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@ -1402,9 +1402,20 @@ void QTabWidget::setTabBarAutoHide(bool enabled)
*/
void QTabWidget::clear()
{
// ### optimize by introduce QStackedLayout::clear()
while (count())
removeTab(0);
Q_D(QTabWidget);
Q_ASSERT(d->stack->layout());
d->stack->layout()->setEnabled(false);
d->stack->setUpdatesEnabled(false);
d->tabs->setUpdatesEnabled(false);
int c = count();
while (c)
removeTab(--c);
d->tabs->setUpdatesEnabled(true);
d->stack->setUpdatesEnabled(true);
d->stack->layout()->setEnabled(true);
d->stack->layout()->activate();
}
QTabBar::Shape _q_tb_tabBarShapeFrom(QTabWidget::TabShape shape, QTabWidget::TabPosition position)