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50
51#include <QOpenGLWindow>
52#include <QScreen>
53#include <QPainter>
54#include <QPainterPath>
55#include <QGuiApplication>
56#include <QMatrix4x4>
57#include <QStaticText>
58#include <QKeyEvent>
59
60#include "background_renderer.h"
61
62static QPainterPath painterPathForTriangle()
63{
64 static const QPointF bottomLeft(-1.0, -1.0);
65 static const QPointF top(0.0, 1.0);
66 static const QPointF bottomRight(1.0, -1.0);
67
68 QPainterPath path(bottomLeft);
69 path.lineTo(p: top);
70 path.lineTo(p: bottomRight);
71 path.closeSubpath();
72 return path;
73}
74
75class OpenGLWindow : public QOpenGLWindow
76{
77 Q_OBJECT
78
79public:
80 OpenGLWindow();
81
82protected:
83 void paintGL() override;
84 void resizeGL(int w, int h) override;
85 void keyPressEvent(QKeyEvent *e) override;
86
87private:
88 void setAnimating(bool enabled);
89
90 QMatrix4x4 m_window_normalised_matrix;
91 QMatrix4x4 m_window_painter_matrix;
92 QMatrix4x4 m_projection;
93 QMatrix4x4 m_view;
94 QMatrix4x4 m_model_triangle;
95 QMatrix4x4 m_model_text;
96
97 FragmentToy m_fragment_toy;
98 QStaticText m_text_layout;
99 bool m_animate;
100};
101
102// Use NoPartialUpdate. This means that all the rendering goes directly to
103// the window surface, no additional framebuffer object stands in the
104// middle. This is fine since we will clear the entire framebuffer on each
105// paint. Under the hood this means that the behavior is equivalent to the
106// manual makeCurrent - perform OpenGL calls - swapBuffers loop that is
107// typical in pure QWindow-based applications.
108OpenGLWindow::OpenGLWindow()
109 : QOpenGLWindow(QOpenGLWindow::NoPartialUpdate)
110 , m_fragment_toy("./background.frag")
111 , m_text_layout("The triangle and this text is rendered with QPainter")
112 , m_animate(true)
113{
114 setGeometry(posx: 300, posy: 300, w: 500, h: 500);
115
116 m_view.lookAt(eye: QVector3D(3,1,1),
117 center: QVector3D(0,0,0),
118 up: QVector3D(0,1,0));
119
120 setAnimating(m_animate);
121}
122
123void OpenGLWindow::paintGL()
124{
125 m_fragment_toy.draw(windowSize: size());
126
127 QPainter p(this);
128 p.setWorldTransform(matrix: m_window_normalised_matrix.toTransform());
129
130 QMatrix4x4 mvp = m_projection * m_view * m_model_triangle;
131 p.setTransform(transform: mvp.toTransform(), combine: true);
132
133 p.fillPath(path: painterPathForTriangle(), brush: QBrush(QGradient(QGradient::NightFade)));
134
135 QTransform text_transform = (m_window_painter_matrix * m_view * m_model_text).toTransform();
136 p.setTransform(transform: text_transform, combine: false);
137 p.setPen(QPen(Qt::black));
138 m_text_layout.prepare(matrix: text_transform);
139 qreal x = - (m_text_layout.size().width() / 2);
140 qreal y = 0;
141 p.drawStaticText(x, y, staticText: m_text_layout);
142
143 m_model_triangle.rotate(angle: -1, x: 0, y: 1, z: 0);
144 m_model_text.rotate(angle: 1, x: 0, y: 1, z: 0);
145}
146
147void OpenGLWindow::resizeGL(int w, int h)
148{
149 m_window_normalised_matrix.setToIdentity();
150 m_window_normalised_matrix.translate(x: w / 2.0, y: h / 2.0);
151 m_window_normalised_matrix.scale(x: w / 2.0, y: -h / 2.0);
152
153 m_window_painter_matrix.setToIdentity();
154 m_window_painter_matrix.translate(x: w / 2.0, y: h / 2.0);
155
156 m_text_layout.setTextWidth(std::max(a: w * 0.2, b: 80.0));
157
158 m_projection.setToIdentity();
159 m_projection.perspective(verticalAngle: 45.f, aspectRatio: qreal(w) / qreal(h), nearPlane: 0.1f, farPlane: 100.f);
160}
161
162void OpenGLWindow::keyPressEvent(QKeyEvent *e)
163{
164 if (e->key() == Qt::Key_P) { // pause
165 m_animate = !m_animate;
166 setAnimating(m_animate);
167 }
168}
169
170void OpenGLWindow::setAnimating(bool enabled)
171{
172 if (enabled) {
173 // Animate continuously, throttled by the blocking swapBuffers() call the
174 // QOpenGLWindow internally executes after each paint. Once that is done
175 // (frameSwapped signal is emitted), we schedule a new update. This
176 // obviously assumes that the swap interval (see
177 // QSurfaceFormat::setSwapInterval()) is non-zero.
178 connect(sender: this, signal: &QOpenGLWindow::frameSwapped,
179 receiver: this, slot: QOverload<>::of(ptr: &QPaintDeviceWindow::update));
180 update();
181 } else {
182 disconnect(sender: this, signal: &QOpenGLWindow::frameSwapped,
183 receiver: this, slot: QOverload<>::of(ptr: &QPaintDeviceWindow::update));
184 }
185}
186
187int main(int argc, char **argv)
188{
189 QGuiApplication app(argc, argv);
190
191 OpenGLWindow window;
192 QSurfaceFormat fmt;
193 fmt.setDepthBufferSize(24);
194 fmt.setStencilBufferSize(8);
195 window.setFormat(fmt);
196 window.show();
197
198 return app.exec();
199}
200
201#include "main.moc"
202

source code of qtbase/examples/opengl/qopenglwindow/main.cpp