Using OpenGL Shader on a QGraphicsView - qt

Question

I am trying to use an OpenGL Shader on a QGrapicsView.
My graphic card is a NVidia GeForce GT 425M. I made my experiments on a Ubuntu 12.04 with the NVidia driver 295.40.
I Create a QMainWindow containing two QGraphicsView, each graphics view are displaying the same scene. On One of the Graphics View, I setup an OpenGL View port.
The OpenGL View Port is a QGLWidget I had overloaded with the loading of the vertex and fragment shader programs.
Look at my QMainWindow constructor :
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
m_scene = new QGraphicsScene(this);
ui->gvShaded->setScene(m_scene);
ui->gvUnshaded->setScene(m_scene);
m_glWidget = new QGLScene();
ui->gvShaded->setViewport(m_glWidget);
m_glWidget->updateGL();
if(m_glWidget->context()->isValid())
{
qDebug()<<"GL Context is valid";
}else
{
qWarning()<<"GL Context is not valid";
}
qDebug() << "Opengl Version : " << m_glWidget->context()->format().openGLVersionFlags();
QBrush brush(QLinearGradient(0,0,20,0));
brush.setColor(Qt::blue);
QGraphicsRectItem* rect = m_scene->addRect(0,0,20,20,QPen(Qt::black), brush);
ui->gvShaded->ensureVisible(rect);
ui->gvUnshaded->ensureVisible(rect);
}
As you can see I instantiate the object QGLScene which is :
class QGLScene : public QGLWidget
{
public:
QGLScene(QWidget* _parent=0);
protected :
virtual void initializeGL();
};
My GLWidget Construction is :
QGLScene::QGLScene(QWidget *_parent)
:QGLWidget(QGLFormat(QGL::DepthBuffer), _parent)
{
}
And definition of initializeGL is :
void QGLScene::initializeGL()
{
qDebug() << __PRETTY_FUNCTION__;
QGLShader fragmentShader(QGLShader::Fragment, context(), this);
QGLShader vertexShader(QGLShader::Vertex, context(), this);
QGLShaderProgram pgm(context(), this);
if(vertexShader.compileSourceFile("./vertexShader.glsl"))
{
if(fragmentShader.compileSourceFile("./fragmentShader.glsl"))
{
pgm.addShader(&fragmentShader);
pgm.addShader(&vertexShader);
pgm.link();
pgm.bind();
qDebug() << "Shader bien chargé : "<< pgm.log();
}else
{
qDebug() << "Problem when loading fragment shader :";
qDebug() << fragmentShader.log();
qDebug() << QString(fragmentShader.sourceCode());
}
}else
{
qDebug() << "Problem when loading vertex shader :";
qDebug() << vertexShader.log();
qDebug() << QString(vertexShader.sourceCode());
}
}
My shaders are very useless shaders :
Vertex :
#version 150
uniform mat4 viewMatrix, projMatrix;
in vec4 position;
in vec3 color;
out vec3 Color;
void main()
{
Color = color;
gl_Position = projMatrix * viewMatrix * position ;
}
Fragment :
#version 150
in vec3 Color;
out vec4 outputF;
void main()
{
outputF = vec4(1.0, 0, 0, 1.);
}
So I attempt to have my Shaded Graphics view as a big red square because I think I enforced the pixels to be red (in my fragment shader).
I have no shader compilation error, but my two scene are the same.
Of course, the program pass into the initializeGL function (I can read the PRETTY_FUNCTION).
Does some one have an explanation ?