Qt 5.6, Windows 7 - getting OpenGL errors (1286, 1280, "Unsupported framebuffer format") in qopenglframebufferobject.cpp

[Arun V]

Hi,

The program I am working on uses QOpenGLWidget to render a 2D image. However, I keep getting OpenGL errors in qopenglframebufferobject.cpp (as described below). The fact that I am relatively new to OpenGL doesn't help matters either!

I use Qt 5.6.0, and OpenGL 2.1.0. OS is Windows 7, display adapter is Intel HD graphics.

A minimal program that reproduces the error is as follows:

#include <GL/glew.h>

#include <QtWidgets/QApplication>

#include <QOpenGLWidget>
#include <QSurfaceFormat>

#include <GL/GLU.h>

#include <iostream>

using namespace std;

class OGLErrorTest : public QOpenGLWidget
{
public:
    OGLErrorTest(QWidget *p = nullptr) : QOpenGLWidget(p) 
    {
        QSurfaceFormat sformat;
        sformat.setProfile(QSurfaceFormat::CompatibilityProfile);
        sformat.setMajorVersion(2);
        sformat.setMinorVersion(1);
        sformat.setDepthBufferSize(0);
        sformat.setAlphaBufferSize(0);
        sformat.setRedBufferSize(8);
        sformat.setGreenBufferSize(8);
        sformat.setBlueBufferSize(8);
        sformat.setStencilBufferSize(0);
        sformat.setSwapBehavior(QSurfaceFormat::DoubleBuffer);
        sformat.setStereo(false);

        setFormat(sformat);
    }

    ~OGLErrorTest() {}

protected:

    void initializeGL() 
    {
        glewExperimental = GL_TRUE;
        GLenum err = glewInit();

        if (err != GLEW_OK) {
            cout << "Failed to initialize GLEW" << endl;
            exit(-1);
        }

        const char *glv = (const char *)glGetString(GL_VERSION);
        glv = glv ? glv : "(unable to get OpenGL version)";
        cout << glv << endl;
    }

    void resizeGL(int w, int h) {}

    void paintGL() 
    {
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        gluOrtho2D(0, 100, 0, 100);

        glColor3f(1.0f, 1.0f, 1.0f);
        glBegin(GL_LINES);
        glVertex2d(0, 0);
        glVertex2d(100, 100);
        glEnd();
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    const char *qt_version = qVersion();
    qt_version = qt_version ? qt_version : "(unable to get qt version)";
    cout << qt_version << endl;

    OGLErrorTest w;
    w.show();
    return a.exec();
}

The output of the above program is:

5.6.0
2.1.0 - Build 8.15.10.2104
[opengl\qopenglframebufferobject.cpp line 538] OpenGL Error: 1286
QOpenGLFramebufferObject: Unsupported framebuffer format.
QOpenGLFramebufferObject: Unsupported framebuffer format.
[opengl\qopenglframebufferobject.cpp line 730] OpenGL Error: 1280

The image gets displayed correctly. Not issues with that.

However, my question: how can I get rid of the two OpenGL errors (1286, 1280) please? Does it look like a Qt problem, or does it look like it can be gotten rid of by (say) properly configuring the OpenGL context? I think Qt is trying to make use of some features that my hardware doesn't support. If that's the case, my question is, how can I find out what these features are, and how can I tell Qt to not expect these features to be available?

I tried looking at the source code (qopenglframebufferobject.cpp), but couldn't figure out anything obvious that can be done to fix the error.

Many thanks in advance!