Qt OpenGL texture won't appear

Question

I'm using Qt to create a simple sprite editor with OpenGL, but the image just doesn't show up, it's just a white quad on the screen.

I have checked my code, and I think everything is right. The quad is of the same size of the image and the texture id is not 0.

Here's my code:

Initialization:

glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glDisable(GL_CULL_FACE);

glViewport(0, 0, width, height);

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, win_width, win_height, 0, -1, 1);
glMatrixMode(GL_MODELVIEW);

Texture loading:

QImage b = QImage(filename);
m_texture = QGLWidget::convertToGLFormat(b);

glGenTextures(1, &m_id);
glBindTexture(GL_TEXTURE_2D, m_id);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,
             m_texture.width(),
             m_texture.height(),
             0, GL_RGBA, GL_UNSIGNED_BYTE,
             m_texture.bits());

Render:

glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);

glBindTexture(GL_TEXTURE_2D, m_id);

glBegin(GL_QUADS);

glTexCoord2f(0.0f, 0.0f);
glVertex2i(0, 0);

glTexCoord2f(1.0f, 0.0f);
glVertex2i(m_texture.width(), 0);

glTexCoord2f(1.0f, 1.0f);
glVertex2i(m_texture.width(), m_texture.height());

glTexCoord2f(0.0f, 1.0f);
glVertex2i(0, m_texture.height());

glEnd();

glBindTexture(GL_TEXTURE_2D, 0);

This is what I'm getting so far:

Answer 1

Try manually setting the OpenGL version to 3.2.

QGLFormat glFormat;
glFormat.setVersion(3, 2);
glFormat.setProfile(QGLFormat::CoreProfile);
QGLFormat::setDefaultFormat(glFormat);

After you do that, print your OpenGL version with glGetString().

If you're still getting 2.1, you didn't set it in the correct OpenGL context. I'm not sure exactly how you're making your OpenGL calls, but I was using QT Creator Designer, and was embedding a QGLWidget within the main window. So I was successfully able to set the OpenGL version by setting it within the MainWindow constructor

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    QGLFormat glFormat;
    glFormat.setVersion(3, 2);
    glFormat.setProfile(QGLFormat::CoreProfile);
    QGLFormat::setDefaultFormat(glFormat);
    ui->setupUi(this);
}