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UI/Qt: Avoid repaint loop in vertical tab bar

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Move tab button geometry updates out of TabBar::paintEvent(). That path
mutates child widgets, and Qt schedules more updates for those buttons.
During painting, that can keep the tab bar dirty and churn CPU.

Update buttons from layout, hover, and current-tab changes instead. Keep
hover bookkeeping in one helper, and skip widget mutators when they are
already in the desired state.
This commit is contained in:
Andreas Kling 2026-06-01 10:50:46 +02:00 committed by Andreas Kling
parent 4cc0ee5f47
commit 3ea52a8447
2 changed files with 33 additions and 14 deletions
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46
UI/Qt/TabBar.cpp
View file

@ -193,6 +193,7 @@ TabBar::TabBar(TabWidget* tab_widget)
});
connect(this, &QTabBar::currentChanged, this, [this](int index) {
ensure_tab_visible(index);
update_tab_button_geometry();
});
}
@ -296,8 +297,6 @@ void TabBar::tabLayoutChange()
void TabBar::paintEvent(QPaintEvent*)
{
update_tab_button_geometry();
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing, true);
@ -530,11 +529,7 @@ void TabBar::mousePressEvent(QMouseEvent* event)
void TabBar::mouseMoveEvent(QMouseEvent* event)
{
if (auto hovered_tab = tab_index_at(event->pos()); hovered_tab != m_hovered_tab_index) {
m_hovered_tab_index = hovered_tab;
start_hover_animation(hovered_tab, hovered_tab >= 0 ? 1.0 : 0.0);
update();
}
set_hovered_tab_index(tab_index_at(event->pos()));
if (count() == 0) {
if (tab_layout() == TabLayout::Horizontal)
@ -561,10 +556,7 @@ void TabBar::mouseMoveEvent(QMouseEvent* event)
void TabBar::leaveEvent(QEvent* event)
{
auto previous_hovered_tab = m_hovered_tab_index;
m_hovered_tab_index = -1;
start_hover_animation(previous_hovered_tab, 0.0);
update();
set_hovered_tab_index(-1);
QTabBar::leaveEvent(event);
}
@ -812,16 +804,36 @@ void TabBar::ensure_tab_visible(int index)
set_vertical_scroll_offset(tab_bottom - height());
}
void TabBar::set_hovered_tab_index(int index)
{
if (m_hovered_tab_index == index)
return;
auto previous_hovered_tab = m_hovered_tab_index;
m_hovered_tab_index = index;
update_tab_button_geometry();
start_hover_animation(index >= 0 ? index : previous_hovered_tab, index >= 0 ? 1.0 : 0.0);
update();
}
void TabBar::update_tab_button_geometry()
{
if (tab_layout() == TabLayout::Horizontal || tab_layout() == TabLayout::VerticalCollapsed)
return;
// Keep this out of paintEvent(): setVisible(), setGeometry(), and raise()
// dirty child widgets, and doing that while painting can schedule another
// tab bar repaint before the current one has finished flushing.
auto place_button = [&](int index, QTabBar::ButtonPosition position, QRect shape_rect) {
auto* button = tabButton(index, position);
if (!button)
return;
button->setVisible(position != QTabBar::RightSide || index == currentIndex() || index == m_hovered_tab_index);
auto should_be_visible = position != QTabBar::RightSide || index == currentIndex() || index == m_hovered_tab_index;
bool did_update_button = false;
if (button->isVisible() != should_be_visible) {
button->setVisible(should_be_visible);
did_update_button = true;
}
auto button_size = button->size();
if (button_size.isEmpty())
@ -831,8 +843,14 @@ void TabBar::update_tab_button_geometry()
auto x = position == QTabBar::RightSide ? shape_rect.right() - button_size.width() - 6 : shape_rect.left() + 6;
auto y = shape_rect.top() + ((shape_rect.height() - button_size.height()) / 2);
button->setGeometry({ { x, y }, button_size });
button->raise();
QRect button_geometry { { x, y }, button_size };
if (button->geometry() != button_geometry) {
button->setGeometry(button_geometry);
did_update_button = true;
}
if (did_update_button)
button->raise();
};
for (int index = 0; index < count(); ++index) {

1
UI/Qt/TabBar.h
View file

@ -93,6 +93,7 @@ private:
int max_vertical_scroll_offset() const;
void set_vertical_scroll_offset(int);
void set_hovered_tab_index(int);
void ensure_tab_visible(int index);
void update_tab_button_geometry();