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// Copyright (C) 2026 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include <QtWidgets>
//! [0]
class CheckBoxStyle : public QProxyStyle
{
public:
using QProxyStyle::QProxyStyle;
void drawPrimitive(PrimitiveElement element, const QStyleOption *option,
QPainter *painter, const QWidget *widget) const override;
};
//! [0]
//! [1]
void CheckBoxStyle::drawPrimitive(PrimitiveElement element, const QStyleOption *option,
QPainter *painter, const QWidget *widget) const
{
if (element != PE_IndicatorCheckBox) {
QProxyStyle::drawPrimitive(element, option, painter, widget);
return;
}
const bool enabled = option->state & State_Enabled;
const QPalette::ColorGroup group = !enabled ? QPalette::Disabled
: option->state & State_Active ? QPalette::Active
: QPalette::Inactive;
const QPalette &palette = option->palette;
const QRect rect = option->rect.adjusted(1, 1, -1, -1);
painter->save();
painter->setRenderHint(QPainter::Antialiasing);
// Frame and background: highlight the frame while the mouse hovers over
// the indicator, and darken the background while it's pressed.
QColor frameColor = palette.color(group, QPalette::Mid);
if (enabled && (option->state & State_MouseOver))
frameColor = palette.color(group, QPalette::Highlight);
const QPalette::ColorRole fillRole =
option->state & State_Sunken ? QPalette::Mid : QPalette::Base;
painter->setPen(frameColor);
painter->setBrush(palette.brush(group, fillRole));
painter->drawRoundedRect(rect, 2, 2);
// Check mark for State_On, a filled square for the partially checked
// State_NoChange, nothing for State_Off.
const QRect inner = rect.adjusted(3, 3, -3, -3);
if (option->state & State_On) {
painter->setPen(QPen(palette.color(group, QPalette::Text), 2));
painter->drawLine(inner.left(), inner.center().y(),
inner.center().x(), inner.bottom());
painter->drawLine(inner.center().x(), inner.bottom(),
inner.right(), inner.top());
} else if (option->state & State_NoChange) {
painter->fillRect(inner, palette.brush(group, QPalette::Text));
}
painter->restore();
}
//! [1]
//! [2]
int main(int argc, char *argv[])
{
QApplication::setStyle(new CheckBoxStyle);
QApplication app(argc, argv);
QCheckBox box("Send me updates");
box.show();
return app.exec();
}
//! [2]