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;
 
 
void SimpleExampleWidget::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setPen(Qt::blue);
    painter.setFont(QFont("Arial", 30));
    painter.drawText(rect(), Qt::AlignCenter, "Qt");
}
 
 
void MyWidget::paintEvent(QPaintEvent *)
{
    QPainter p;
    p.begin(this);
    p.drawLine(drawingCode);        // drawing code
    p.end();
}
 
} // 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;
 
void MyWidget::paintEvent(QPaintEvent *)
{
    QPainter p(this);
    p.drawLine(drawingCode);        // drawing code
}
 
 
void wrapper0() {
QPainter *painter = nullptr;
QPainter *painter2 = nullptr;
QPaintDevice *myWidget = nullptr;
painter->begin(0); // impossible - paint device cannot be 0
 
QPixmap image(0, 0);
painter->begin(&image); // impossible - image.isNull() == true;
 
painter->begin(myWidget);
painter2->begin(myWidget); // impossible - only one painter at a time
 
} // wrapper0
 
namespace QPainterWrapper {
struct QPainter {
    void rotate(qreal angle);
    void setWorldTransform(QTransform matrix, bool);
};
 
} // QPainterWrapper
 
void MyWidget::wrapper1() {
QPainterPath path;
path.moveTo(20, 80);
path.lineTo(20, 30);
path.cubicTo(80, 0, 50, 50, 80, 80);
 
QPainter painter(this);
painter.drawPath(path);
 
 
QLineF line(10.0, 80.0, 90.0, 20.0);
 
QPainter painter(this);
painter.drawLine(line);
} // MyWidget::wrapper1()
 
 
void MyWidget::wrapper2() {
 
QRectF rectangle(10.0, 20.0, 80.0, 60.0);
 
QPainter painter(this);
painter.drawRect(rectangle);
 
} // MyWidget::wrapper2
 
 
void MyWidget::wrapper3() {
 
QRectF rectangle(10.0, 20.0, 80.0, 60.0);
 
QPainter painter(this);
painter.drawRoundedRect(rectangle, 20.0, 15.0);
 
} // MyWidget::wrapper3
 
 
void MyWidget::wrapper4() {
 
QRectF rectangle(10.0, 20.0, 80.0, 60.0);
 
QPainter painter(this);
painter.drawEllipse(rectangle);
 
} // MyWidget::wrapper4
 
 
void MyWidget::wrapper5() {
 
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);
 
} // MyWidget::wrapper5
 
 
void MyWidget::wrapper6() {
 
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);
 
} // MyWidget::wrapper6
 
 
void MyWidget::wrapper7() {
QRect rect;
 
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);
Q_UNUSED(rectangle);
} // MyWidget::wrapper7
 
 
void MyWidget::wrapper8() {
 
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);
 
} // MyWidget::wrapper8
 
 
void MyWidget::wrapper9() {
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);
 
} // MyWidget::wrapper9
 
 
void MyWidget::wrapper10() {
 
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);
 
 
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);
 
} // MyWidget::wrapper10
 
 
void MyWidget::wrapper11() {
QRect rect;
 
QPainter painter(this);
painter.drawText(rect, Qt::AlignCenter, tr("Qt\nProject"));
 
} // MyWidget::wrapper11
 
 
QRectF fillRect(QRect rect, int background) {
    Q_UNUSED(rect);
    Q_UNUSED(background);
    return QRectF();
};
void MyWidget::wrapper12() {
QRect rectangle;
 
QPicture picture;
QPointF point(10.0, 20.0);
picture.load("drawing.pic");
 
QPainter painter(this);
painter.drawPicture(0, 0, picture);
 
Q_UNUSED(point);
 
 
fillRect(rectangle, background());
 
} // MyWidget::wrapper12
 
 
void MyWidget::wrapper13() {
 
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);
 
} // MyWidget::wrapper13
 
 
void MyWidget::wrapper14() {
 
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();
 
} // MyWidget::wrapper14
 
 
void MyWidget::wrapper15() {
 
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()));
 
 
} // MyWidget::wrapper15
 
void MyWidget::concentricCircles()
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
    int diameter = 50;
    painter.drawEllipse(QRectF(-diameter / 2.0, -diameter / 2.0, diameter, diameter));
    painter.drawEllipse(QRect(-diameter / 2, -diameter / 2, diameter, diameter));
 
} // MyWidget::concentricCircles
 
} // src_gui_painting_qpainter2