Qt 5.11 | Qt GUI | OpenGL Window Example | main.cpp Example File

Qt 5.11.3 Reference Documentation

# 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;
      }