src_gui_painting_qpainter.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include <QOpenGLFunctions>
#include <QPaintEvent>
#include <QPainter>
#include <QPainterPath>
#include <QPicture>
#include <QRectF>
#include <QWidget>
 
 
namespace src_gui_painting_qpainter {
struct SimpleExampleWidget : public QPaintDevice {
    void paintEvent(QPaintEvent *);
    QRect rect();
};
struct MyWidget : public QWidget
{
    void paintEvent(QPaintEvent *);
};
QLine drawingCode;
 
 
//! [0]
void SimpleExampleWidget::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setPen(Qt::blue);
    painter.setFont(QFont("Arial", 30));
    painter.drawText(rect(), Qt::AlignCenter, "Qt");
}
//! [0]
 
 
//! [1]
void MyWidget::paintEvent(QPaintEvent *)
{
    QPainter p;
    p.begin(this);
    p.drawLine(drawingCode);        // drawing code
    p.end();
}
//! [1]
 
} // src_gui_painting_qpainter
namespace src_gui_painting_qpainter2 {
struct MyWidget : public QWidget
{
    void paintEvent(QPaintEvent *);
    int background() { return 0; }
    void wrapper1();
    void wrapper2();
    void wrapper3();
    void wrapper4();
    void wrapper5();
    void wrapper6();
    void wrapper7();
    void wrapper8();
    void wrapper9();
    void wrapper10();
    void wrapper11();
    void wrapper12();
    void wrapper13();
    void wrapper14();
    void wrapper15();
    void concentricCircles();
};
QLine drawingCode;
 
//! [2]
void MyWidget::paintEvent(QPaintEvent *)
{
    QPainter p(this);
    p.drawLine(drawingCode);        // drawing code
}
//! [2]
 
 
void wrapper0()
{
    QPainter *painter = nullptr;
    QPainter *painter2 = nullptr;
    QPaintDevice *myWidget = nullptr;
    //! [3]
    painter->begin(nullptr); // impossible - paint device cannot be null
 
    QPixmap image(0, 0);
    painter->begin(&image); // impossible - image.isNull() == true;
 
    painter->begin(myWidget);
    painter2->begin(myWidget); // impossible - only one painter at a time
    //! [3]
} // wrapper0
 
namespace QPainterWrapper
{
    struct QPainter {
        void rotate(qreal angle);
        void setWorldTransform(QTransform matrix, bool);
    };
} // QPainterWrapper
 
void MyWidget::wrapper1()
{
    {
    //! [5]
    QPainterPath path;
    path.moveTo(20, 80);
    path.lineTo(20, 30);
    path.cubicTo(80, 0, 50, 50, 80, 80);
 
    QPainter painter(this);
    painter.drawPath(path);
    //! [5]
    }
 
    {
    //! [6]
    QLineF line(10.0, 80.0, 90.0, 20.0);
 
    QPainter painter(this);
    painter.drawLine(line);
    //! [6]
    }
} // MyWidget::wrapper1()
 
 
void MyWidget::wrapper2()
{
    //! [7]
    QRectF rectangle(10.0, 20.0, 80.0, 60.0);
 
    QPainter painter(this);
    painter.drawRect(rectangle);
    //! [7]
} // MyWidget::wrapper2
 
 
void MyWidget::wrapper3()
{
    //! [8]
    QRectF rectangle(10.0, 20.0, 80.0, 60.0);
 
    QPainter painter(this);
    painter.drawRoundedRect(rectangle, 20.0, 15.0);
    //! [8]
} // MyWidget::wrapper3
 
 
void MyWidget::wrapper4()
{
    //! [9]
    QRectF rectangle(10.0, 20.0, 80.0, 60.0);
 
    QPainter painter(this);
    painter.drawEllipse(rectangle);
    //! [9]
} // MyWidget::wrapper4
 
 
void MyWidget::wrapper5()
{
    //! [10]
    QRectF rectangle(10.0, 20.0, 80.0, 60.0);
    int startAngle = 30 * 16;
    int spanAngle = 120 * 16;
 
    QPainter painter(this);
    painter.drawArc(rectangle, startAngle, spanAngle);
    //! [10]
} // MyWidget::wrapper5
 
 
void MyWidget::wrapper6()
{
    //! [11]
    QRectF rectangle(10.0, 20.0, 80.0, 60.0);
    int startAngle = 30 * 16;
    int spanAngle = 120 * 16;
 
    QPainter painter(this);
    painter.drawPie(rectangle, startAngle, spanAngle);
    //! [11]
} // MyWidget::wrapper6
 
 
void MyWidget::wrapper7() {
QRect rect;
 
//! [12]
QRectF rectangle(10.0, 20.0, 80.0, 60.0);
int startAngle = 30 * 16;
int spanAngle = 120 * 16;
 
QPainter painter(this);
painter.drawChord(rect, startAngle, spanAngle);
//! [12]
Q_UNUSED(rectangle);
} // MyWidget::wrapper7
 
 
void MyWidget::wrapper8()
{
    //! [13]
    static const QPointF points[3] = {
        QPointF(10.0, 80.0),
        QPointF(20.0, 10.0),
        QPointF(80.0, 30.0),
    };
 
    QPainter painter(this);
    painter.drawPolyline(points, 3);
    //! [13]
} // MyWidget::wrapper8
 
 
void MyWidget::wrapper9()
{
    //! [14]
    static const QPointF points[4] = {
        QPointF(10.0, 80.0),
        QPointF(20.0, 10.0),
        QPointF(80.0, 30.0),
        QPointF(90.0, 70.0)
    };
 
    QPainter painter(this);
    painter.drawPolygon(points, 4);
    //! [14]
} // MyWidget::wrapper9
 
 
void MyWidget::wrapper10()
{
    {
    //! [15]
    static const QPointF points[4] = {
        QPointF(10.0, 80.0),
        QPointF(20.0, 10.0),
        QPointF(80.0, 30.0),
        QPointF(90.0, 70.0)
    };
 
    QPainter painter(this);
    painter.drawConvexPolygon(points, 4);
    //! [15]
    }
 
    {
    //! [16]
    QRectF target(10.0, 20.0, 80.0, 60.0);
    QRectF source(0.0, 0.0, 70.0, 40.0);
    QPixmap pixmap(":myPixmap.png");
 
    QPainter painter(this);
    painter.drawPixmap(target, pixmap, source);
    //! [16]
    }
} // MyWidget::wrapper10
 
 
void MyWidget::wrapper11()
{
    QRect rect;
 
    //! [17]
    QPainter painter(this);
    painter.drawText(rect, Qt::AlignCenter, tr("Qt\nProject"));
    //! [17]
} // MyWidget::wrapper11
 
 
QRectF fillRect(QRect rect, int background) {
    Q_UNUSED(rect);
    Q_UNUSED(background);
    return QRectF();
};
 
void MyWidget::wrapper12()
{
    QRect rectangle;
 
    //! [18]
    QPicture picture;
    QPointF point(10.0, 20.0);
    picture.load("drawing.pic");
 
    QPainter painter(this);
    painter.drawPicture(0, 0, picture);
    //! [18]
 
    Q_UNUSED(point);
 
 
    //! [19]
    fillRect(rectangle, background());
    //! [19]
} // MyWidget::wrapper12
 
 
void MyWidget::wrapper13()
{
    //! [20]
    QRectF target(10.0, 20.0, 80.0, 60.0);
    QRectF source(0.0, 0.0, 70.0, 40.0);
    QImage image(":/images/myImage.png");
 
    QPainter painter(this);
    painter.drawImage(target, image, source);
    //! [20]
} // MyWidget::wrapper13
 
 
void MyWidget::wrapper14()
{
    //! [21]
    QPainter painter(this);
    painter.fillRect(0, 0, 128, 128, Qt::green);
    painter.beginNativePainting();
 
    glEnable(GL_SCISSOR_TEST);
    glScissor(0, 0, 64, 64);
 
    glClearColor(1, 0, 0, 1);
    glClear(GL_COLOR_BUFFER_BIT);
 
    glDisable(GL_SCISSOR_TEST);
 
    painter.endNativePainting();
    //! [21]
} // MyWidget::wrapper14
 
 
void MyWidget::wrapper15()
{
    //! [drawText]
    QPainter painter(this);
    QFont font = painter.font();
    font.setPixelSize(48);
    painter.setFont(font);
 
    const QRect rectangle = QRect(0, 0, 100, 50);
    QRect boundingRect;
    painter.drawText(rectangle, 0, tr("Hello"), &boundingRect);
 
    QPen pen = painter.pen();
    pen.setStyle(Qt::DotLine);
    painter.setPen(pen);
    painter.drawRect(boundingRect.adjusted(0, 0, -pen.width(), -pen.width()));
 
    pen.setStyle(Qt::DashLine);
    painter.setPen(pen);
    painter.drawRect(rectangle.adjusted(0, 0, -pen.width(), -pen.width()));
    //! [drawText]
} // MyWidget::wrapper15
 
void MyWidget::concentricCircles()
{
    //! [renderHint]
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
    //! [renderHint]
    int diameter = 50;
    //! [floatBased]
    painter.drawEllipse(QRectF(-diameter / 2.0, -diameter / 2.0, diameter, diameter));
    //! [floatBased]
    //! [intBased]
    painter.drawEllipse(QRect(-diameter / 2, -diameter / 2, diameter, diameter));
    //! [intBased]
 
} // MyWidget::concentricCircles
 
} // src_gui_painting_qpainter2