Using GLEW with QOpenGLWidget - qt

Question

I'm trying to use GLEW with QT in a QOpenGLWidget in Visual Studio.
Some details:
Visual Studio 2013
Glew 2.0.0 x64
QT 5.6.2 x64
I keep getting "Missing GL version" error when calling glewInit(). I've searched online a lot, and this problem seems to sometimes be caused by how the format is set (QSurfaceFormat), or how the functions create()/ makeCurrent() / doneCurrent() are used. But I can't seem to find a working solution. I'm still a bit confused about the whole QOpenGLContext thing also.
I manage to get the QOpenGLWidget work without GLEW, and using "old" gl functions (glBegin(), glEnd(), etc...). And I also get GLEW to work with GLFW3.
Is there something I seem to misunderstand in the code below?
My subclass of QOpenGLWidget
MyGLWidget.h
#pragma once
#include <QWidget>
#include "GL\glew.h"
#include <QOpenGLWidget>
#include <gl/GLU.h>
#include <gl/GL.h>
#include <iostream>
#include "qopenglcontext.h"
#include "loadShader.h"
class MyGLWidget : public QOpenGLWidget
{
public:
MyGLWidget(QWidget *parent = 0);
~MyGLWidget();
public:
void initializeGL() override;
void resizeGL(int w, int h) override;
void paintGL() override;
};
MyGLWidget.cpp
#include "MyGLWidget.h"
MyGLWidget::MyGLWidget(QWidget *parent)
: QOpenGLWidget(parent)
{
QSurfaceFormat glformat;
glformat.setVersion(3, 2);
glformat.setOption(QSurfaceFormat::DeprecatedFunctions);
glformat.setSwapBehavior(QSurfaceFormat::DoubleBuffer);
glformat.setProfile(QSurfaceFormat::CompatibilityProfile);
QSurfaceFormat::setDefaultFormat(glformat);
this->setFormat(glformat);
create();
makeCurrent();
}
MyGLWidget::~MyGLWidget(){}
void MyGLWidget::initializeGL()
{
glewExperimental = TRUE;
GLenum err = glewInit();
if (GLEW_OK != err){
std::cout << "[Error] GLEW failed to initialize. " << (const char*)glewGetErrorString(err);
}
doneCurrent();
GLuint TextShader_ID = LoadShaders("Shaders/TextVertShader.vert", "Shaders/TextFragShader.frag");
}
void MyGLWidget::paintGL()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
}
void MyGLWidget::resizeGL(int w, int h)
{
//...
}
main.cpp
#include "OGLQT_test2.h"
#include <QtWidgets/QApplication>
#include "GL\glew.h"
#include <QOpenGLFunctions>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
OGLQT_test2 w;
w.show();
return a.exec();
}
OGLQT_test2.h
#pragma once
#include "GL\glew.h"
#include <QtWidgets/QMainWindow>
#include "ui_OGLQT_test2.h"
#include "qopenglcontext.h"
class OGLQT_test2 : public QMainWindow
{
Q_OBJECT
public:
OGLQT_test2(QWidget *parent = Q_NULLPTR);
private:
Ui::OGLQT_test2Class ui;
};
OGLQT_test2.cpp
#include "OGLQT_test2.h"
#include "MyGLWidget.h"
OGLQT_test2::OGLQT_test2(QWidget *parent)
: QMainWindow(parent)
{
ui.setupUi(this);
MyGLWidget* glwidget = new MyGLWidget(this);
glwidget->setFixedHeight(400);
glwidget->setFixedWidth(500);
glwidget->move(50, 50);
glwidget->initializeGL();
glwidget->resizeGL(400,500);
glwidget->paintGL();
}

Answer 1

It seems that you cannot do this:
glformat.setVersion(x, y);
with GLEW. It works with QOpenGLFunctions, but apparently, it doesn't work with GLEW. You may not be able to do this, either:
glformat.setOption(QSurfaceFormat::DeprecatedFunctions);
glformat.setSwapBehavior(QSurfaceFormat::DoubleBuffer);
glformat.setProfile(QSurfaceFormat::CompatibilityProfile);
Try removing the format.
Also, I think you're doing a little bit of a mess here:
glwidget->initializeGL();
glwidget->resizeGL(400,500);
glwidget->paintGL();
There is a simple way to do this, just do:
glwidget->resize(400,500);
glwidget->show();
resizeGL is an event called by resize. That goes the same for initializeGL() and paintGL() being called by show.
Another one is:
GLenum err = glewInit();
if (GLEW_OK != err){
std::cout << "[Error] GLEW failed to initialize. " << (const char*)glewGetErrorString(err);
}
doneCurrent();
Now why would you call doneCurrent here?