Qt QOpenGLWidget crash when call glewInit() with error : Missing GL version

Question

I use Qt to create a 3D program with GLEW. I have a problem when I call glewInit() from run-time creating Widget. I create an inherited class , MyRender, based on QOpenGLWidget. Then, implemented initializeGL() with

GLenum err;
if( err = glewInit() )
{
    printf( "error because: %s\n", glewGetErrorString( err )  );
    exit(123);
}

Normally, I use class MyRender via Qt Designer and promote QOpenGLWidget to MyRender. Then I will have MyRender Object since the program starts. There is no problem.

However, when I create MyRender at Run-time. For example;

MyRender * myrender = new MyRender ( this );

The program will crash when calling glewInit()

Missing GL version   // glewInit() problem

I found the people who have the same problem as me from this

However, in the post, people use either GLUT or SDL to create context. Since I use only GLEW how could I make the context from QOpenglWidget the same way as

glutInitDisplayMode(GLUT_RGB); //use GLUT

or

sf::Window   App(sf::VideoMode(400, 400, 32), "Window"); //use SDL

or

glfwMakeContextCurrent    // use glfw

Since I use none of them. I use only QOpenGLWidget and glew. I tried with

myrender->makeCurrent(); // fail
myrender->initializeGL(); // fail

before calling

glewInit()

however, the problem still persists.

About my machine: I use Windows 10 64-bit. Qt 5.11 GLEW 2.1.0

EDIT:

I test my code with

 void initializeGL()
 {
        echo("inside initializeGL");

        QOpenGLContext* current = this->context();
        if( current == nullptr )
        {
            printf("current context is null\n");
            exit(123);
        }
        else
        {
           printf("current context is good\n");
        }

        GLenum err = glewInit();  // error here
        ...
 }

If I use Qt Designer to promote openGLWidget to MyRender . the context will be OK; However, if I create MyRender in Run-time

MyRender* myrender = new MyRender( this );

The context will be null and leads glewInit() error.

score 0 · Answer 1 · answered Apr 11 '19 at 06:28

I found that the problem is context is not created, and when the program call function initializeGL(). The solution that I did is I call show(); right after creating the widget.

myrender = new MyRender( ui->mdiArea );
myrender->show(); // this line make the context for QOpenGLWidget I think..

... 
// note class MyRender is an inherited class from QOpenGLWidget

Qt QOpenGLWidget crash when call glewInit() with error : Missing GL version

1 Answers1