QT5 and opengl core profile not show me simple shader - qt

Question

i'm a new member and i have a question.
I want to develope a simple project with QT5 and opengl core profile for an end term project.
I first tried with a simple example but nothing happen. The screen show me only the red background but not the shader that i have write.
the code is the following:
main.cpp
#include <QApplication>
#include <QGLFormat>
#include "glwidget.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
//specify oepngl version and other stuff
QGLFormat glFormat;
glFormat.setVersion(4, 3);
glFormat.setProfile(QGLFormat::CoreProfile);
glFormat.setSampleBuffers(true);
GLWidget w(glFormat);
w.show();
return a.exec();
}
glwidget.h
#ifndef GLWIDGET_H
#define GLWIDGET_H
#include <QGLWidget>
#include <QGLBuffer>
#include <QGLShaderProgram>
#include <QOpenGLVertexArrayObject>
class GLWidget : public QGLWidget
{
Q_OBJECT
public:
GLWidget(const QGLFormat& format, QWidget* parent = 0);
protected:
virtual void initializeGL();
virtual void resizeGL(int w, int h);
virtual void paintGL();
//virtual void keyPressEvent(QKeyEvent* e);
private:
bool prepareShaderProgram(const QString& vertexShaderPath, const QString& fragmentShaderPath);
QGLShaderProgram m_shader;
QGLBuffer m_vertexBuffer;
GLuint vertex_array_object;
};
#endif // GLWIDGET_H
glwidget.cpp
#include "glwidget.h"
GLWidget::GLWidget(const QGLFormat& format, QWidget* parent)
:QGLWidget(format, parent),
m_vertexBuffer(QGLBuffer::VertexBuffer)
{
}
void GLWidget::initializeGL()
{
QGLFormat glFormat = QGLWidget::format();
if(!glFormat.sampleBuffers())
qWarning() << "Can't enable sample buffers";
//set background color
glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
//load the shaders
if(!prepareShaderProgram("/home/sera/workspace/qtWorkspace/provaShader/simple.vert",
"/home/sera/workspace/qtWorkspace/provaShader/simple.frag"))
return;
//create and bind the vertex buffer to the context
m_vertexBuffer.create();
if(!m_vertexBuffer.bind())
{
qWarning() << "could not bind vertex buffer to the opengl context";
return;
}
//bind program to the context
if(!m_shader.bind())
{
qWarning() << "could not bind shader program to the context";
return;
}
}
bool GLWidget::prepareShaderProgram(const QString &vertexShaderPath, const QString &fragmentShaderPath)
{
//load and compile shaders
bool result = m_shader.addShaderFromSourceFile(QGLShader::Vertex, vertexShaderPath);
if(!result)
qWarning() << m_shader.log();
result = m_shader.addShaderFromSourceFile(QGLShader::Fragment, fragmentShaderPath);
if(!result)
qWarning() << m_shader.log();
//link shaders into program
result = m_shader.link();
if(!result)
qWarning() << "could not link shader program" << m_shader.log();
return result;
}
void GLWidget::resizeGL(int w, int h)
{
//set the viewport
glViewport(0, 0, w, qMax(h, 1));
}
void GLWidget::paintGL()
{
//clear buffer with current color
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPointSize(40.0);
glDrawArrays(GL_POINTS, 0, 1);
}
/*
void GLWidget::keyPressEvent( QKeyEvent* e )
{
switch (e->key())
{
case Qt::Key_Escape:
QCoreApplication::instance()->quit();
break;
default:
QGLWidget::keyPressEvent( e );
}
}
*/
simple.vert
#version 430 core
void main(void)
{
gl_Position = vec4(1.0, 0.0, 0.0, 1.0);
}
simple.frag
#version 430 core
out vec4 color;
void main(void)
{
color = vec4(1.0, 1.0, 1.0, 1.0);
}
And the result is this in the figure, but i'm aspected a point in the middle
result
What is wrong?