- Qt 5.5
- Qt GUI
- OpenGL Window Example
- main.cpp Example File
- Qt 5.5.1 Reference Documentation

# main.cpp Example File

openglwindow/main.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the documentation of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
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    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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    #include "openglwindow.h"

    #include <QtGui/QGuiApplication>
    #include <QtGui/QMatrix4x4>
    #include <QtGui/QOpenGLShaderProgram>
    #include <QtGui/QScreen>

    #include <QtCore/qmath.h>

    class TriangleWindow : public OpenGLWindow
    {
    public:
        TriangleWindow();

        void initialize() Q_DECL_OVERRIDE;
        void render() Q_DECL_OVERRIDE;

    private:
        GLuint loadShader(GLenum type, const char *source);

        GLuint m_posAttr;
        GLuint m_colAttr;
        GLuint m_matrixUniform;

        QOpenGLShaderProgram *m_program;
        int m_frame;
    };

    TriangleWindow::TriangleWindow()
        : m_program(0)
        , m_frame(0)
    {
    }

    int main(int argc, char **argv)
    {
        QGuiApplication app(argc, argv);

        QSurfaceFormat format;
        format.setSamples(16);

        TriangleWindow window;
        window.setFormat(format);
        window.resize(640, 480);
        window.show();

        window.setAnimating(true);

        return app.exec();
    }

    static const char *vertexShaderSource =
        "attribute highp vec4 posAttr;\n"
        "attribute lowp vec4 colAttr;\n"
        "varying lowp vec4 col;\n"
        "uniform highp mat4 matrix;\n"
        "void main() {\n"
        "   col = colAttr;\n"
        "   gl_Position = matrix * posAttr;\n"
        "}\n";

    static const char *fragmentShaderSource =
        "varying lowp vec4 col;\n"
        "void main() {\n"
        "   gl_FragColor = col;\n"
        "}\n";

    GLuint TriangleWindow::loadShader(GLenum type, const char *source)
    {
        GLuint shader = glCreateShader(type);
        glShaderSource(shader, 1, &source, 0);
        glCompileShader(shader);
        return shader;
    }

    void TriangleWindow::initialize()
    {
        m_program = new QOpenGLShaderProgram(this);
        m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
        m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);
        m_program->link();
        m_posAttr = m_program->attributeLocation("posAttr");
        m_colAttr = m_program->attributeLocation("colAttr");
        m_matrixUniform = m_program->uniformLocation("matrix");
    }

    void TriangleWindow::render()
    {
        const qreal retinaScale = devicePixelRatio();
        glViewport(0, 0, width() * retinaScale, height() * retinaScale);

        glClear(GL_COLOR_BUFFER_BIT);

        m_program->bind();

        QMatrix4x4 matrix;
        matrix.perspective(60.0f, 4.0f/3.0f, 0.1f, 100.0f);
        matrix.translate(0, 0, -2);
        matrix.rotate(100.0f * m_frame / screen()->refreshRate(), 0, 1, 0);

        m_program->setUniformValue(m_matrixUniform, matrix);

        GLfloat vertices[] = {
            0.0f, 0.707f,
            -0.5f, -0.5f,
            0.5f, -0.5f
        };

        GLfloat colors[] = {
            1.0f, 0.0f, 0.0f,
            0.0f, 1.0f, 0.0f,
            0.0f, 0.0f, 1.0f
        };

        glVertexAttribPointer(m_posAttr, 2, GL_FLOAT, GL_FALSE, 0, vertices);
        glVertexAttribPointer(m_colAttr, 3, GL_FLOAT, GL_FALSE, 0, colors);

        glEnableVertexAttribArray(0);
        glEnableVertexAttribArray(1);

        glDrawArrays(GL_TRIANGLES, 0, 3);

        glDisableVertexAttribArray(1);
        glDisableVertexAttribArray(0);

        m_program->release();

        ++m_frame;
    }