main.cpp Example File | Qt GUI 5.12.12

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- main.cpp Example File
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# main.cpp Example File

openglwindow/main.cpp

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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() override;
         void render() override;

     private:
         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";

     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;
     }