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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include <QGraphicsEffect>
#include <QPainter>
#include <QLinearGradient>
#include <QGraphicsOpacityEffect>
#include <QRect>
class MyGraphicsEffect : public QGraphicsEffect
{
Q_OBJECT
public:
void draw(QPainter *painter) override;
};
class MyGraphicsOpacityEffect : public QGraphicsOpacityEffect
{
Q_OBJECT
public:
void draw(QPainter *painter) override;
private:
qreal m_opacity = 1.0;
};
//! [0]
void MyGraphicsOpacityEffect::draw(QPainter *painter)
{
// Fully opaque; draw directly without going through a pixmap.
if (qFuzzyCompare(m_opacity, 1)) {
drawSource(painter);
return;
}
//...
}
//! [0]
//! [1]
void MyGraphicsEffect::draw(QPainter *painter)
{
//...
QPoint offset;
if (sourceIsPixmap()) {
// No point in drawing in device coordinates (pixmap will be scaled anyways).
const QPixmap pixmap = sourcePixmap(Qt::LogicalCoordinates, &offset);
//...
painter->drawPixmap(offset, pixmap);
} else {
// Draw pixmap in device coordinates to avoid pixmap scaling;
const QPixmap pixmap = sourcePixmap(Qt::DeviceCoordinates, &offset);
painter->setWorldTransform(QTransform());
//...
painter->drawPixmap(offset, pixmap);
}
//...
}
//! [1]
void example()
{
QRect rect;
//! [2]
//...
QLinearGradient alphaGradient(rect.topLeft(), rect.bottomLeft());
alphaGradient.setColorAt(0.0, Qt::transparent);
alphaGradient.setColorAt(0.5, Qt::black);
alphaGradient.setColorAt(1.0, Qt::transparent);
QGraphicsOpacityEffect *effect = new QGraphicsOpacityEffect;
effect->setOpacityMask(alphaGradient);
//...
//! [2]
}