Using-QOpenGLFunctions-and-QOpenGLContext

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This simple examle demonstrates to using QOpenGLFunctions and QOpenGLContext. OpenGL 3.3 Core Profile support require for compile and run this demo.According to recent Qt 5.2.0

 //////////// FOR BUILD///////////

//g++ -fPIC -I/usr/include/qt -I/usr/include/qt/QtGui -I/usr/include/qt/QtCore main.cpp -lQt5Gui -lQt5Core -lGL -lpthread

#include <QGuiApplication>
#include <QOpenGLContext>
#include <QWindow>
#include <QOpenGLFunctions_3_3_Core>
#include <stdio.h>

class OpenGLWindow : public QWindow, protected QOpenGLFunctions_3_3_Core{

 public:
 explicit OpenGLWindow();
 ~OpenGLWindow();
 virtual void render();
 bool isWindowInitialized;
 void exposeEvent(QExposeEvent *event);
 bool event(QEvent '''event);

 private:
 QOpenGLContext''' ctx;
 QSurfaceFormat* fmt;
 bool isGLInitialized;
 GLuint VertexArrayID;
 GLuint buffer1;
 GLuint ProgramID;
}; 

bool OpenGLWindow::event(QEvent *event)
{
 switch (event->type()) {
 case QEvent::UpdateRequest:
 render();
 return true;
 case QEvent::Close:
 glDisableVertexAttribArray(0);
 glDeleteBuffers(1, &buffer1);
 glDeleteVertexArrays(1, &VertexArrayID);
 glDeleteProgram(ProgramID);
 return QWindow::event(event);
 case QEvent::Resize:
 if(isWindowInitialized && isGLInitialized)glViewport(0,0,width(),height());
 return QWindow::event(event);
 default:
 return QWindow::event(event);
 }
}

void OpenGLWindow::exposeEvent(QExposeEvent *event)
{
 Q_UNUSED(event);
 if (isExposed())render();
}

OpenGLWindow::OpenGLWindow()
 :ctx(new QOpenGLContext)
 ,fmt(new QSurfaceFormat)
 ,isGLInitialized(0)
{
 setSurfaceType(OpenGLSurface);
 fmt->setRenderableType(QSurfaceFormat::OpenGL);
 fmt->setVersion(3,3);
 resize(640,480);
 fmt->setProfile(QSurfaceFormat::CoreProfile);
 setFormat(*fmt);
 ctx->setFormat('''fmt);
 ctx->create();
}

OpenGLWindow::~OpenGLWindow()
{}

void OpenGLWindow::render(){

 if([[Image:isWindowInitialized || |]]isExposed())return;

 if(!isGLInitialized){

 ctx->makeCurrent(this);
 initializeOpenGLFunctions();

 GLuint vsID = glCreateShader(GL_VERTEX_SHADER);
 GLuint fsID = glCreateShader(GL_FRAGMENT_SHADER);

 const char''' vs="#version 330 coren layout(location = 0) in vec3 vertexPosition_modelspace;void main(){ gl_Position.xyz = vertexPosition_modelspace; gl_Position.w = 1.0;}";

const char* fs="#version 330 coren out vec3 color; void main(){ color = vec3(1,0,0);}";

glShaderSource(vsID, 1, &vs , NULL);
 glCompileShader(vsID);
 GLint isCompiled = 0;
 glGetShaderiv(vsID, GL_COMPILE_STATUS, &isCompiled);

if(isCompiled == GL_FALSE){
 GLint maxLength = 0;
 glGetShaderiv(vsID, GL_INFO_LOG_LENGTH, &maxLength);
 char info[maxLength];
 glGetShaderInfoLog(vsID, maxLength, &maxLength, info);
 printf("%s",info);}

glShaderSource(fsID, 1, &fs , NULL);
 glCompileShader(fsID);
 glGetShaderiv(fsID, GL_COMPILE_STATUS, &isCompiled);

if(isCompiled == GL_FALSE){
 GLint maxLength = 0;
 glGetShaderiv(fsID, GL_INFO_LOG_LENGTH, &maxLength);
 char info[maxLength];
 glGetShaderInfoLog(fsID, maxLength, &maxLength, info);
 printf("%s",info);}

GLuint ProgramID = glCreateProgram();
 glAttachShader(ProgramID, vsID);
 glAttachShader(ProgramID, fsID);
 glLinkProgram(ProgramID);
 glDeleteShader(vsID);
 glDeleteShader(fsID);

static const GLfloat data1[] = {
 –1.0f, –1.0f, 0.0f,
 1.0f, -1.0f, 0.0f,
 0.0f, 1.0f, 0.0f,
 };

 glGenVertexArrays(1, &VertexArrayID);
 glBindVertexArray(VertexArrayID);
 glGenBuffers(1, &buffer1);
 glBindBuffer(GL_ARRAY_BUFFER,buffer1);
 glBufferData(GL_ARRAY_BUFFER, sizeof(data1),data1, GL_STATIC_DRAW);
 glEnableVertexAttribArray(0);
 glVertexAttribPointer(0 ,3 ,GL_FLOAT ,GL_FALSE,0 ,(void*)0 );
 glClearColor(0.0f, 0.0f, 0.4f,1.0f);
 glUseProgram(ProgramID);
 glViewport(0,0,width(),height());
 isGLInitialized=true;
 }

 if(isExposed()){
 glClear( GL_COLOR_BUFFER_BIT );
 glDrawArrays(GL_TRIANGLES, 0, 3);
 ctx->swapBuffers(this);
 }
}

int main(int argc, char *'''argv)
{
 QGuiApplication app(argc, argv);
 OpenGLWindow''' win = new OpenGLWindow();
 win->show();
 win->isWindowInitialized=true;
 return app.exec();
}

This demo tested on kernel 3.12.8 mesa 10.0.2 xorg 1.15 and intel ivy bridge graphics.Worked perfectly.