Obtain OpenGL version from OSG

osg-openGL-version.cpp

#include <iostream>
#include <stdio.h>

#ifdef _WIN32
#include <Windows.h>
#endif

#include <osgViewer/Viewer>
#include <osg/GLExtensions>

const int OSG_WIDTH = 1024;
const int OSG_HEIGHT = 960;

class TestSupportOperation : public osg::GraphicsOperation
{
public:
    TestSupportOperation()
        : osg::Referenced(true)
        , osg::GraphicsOperation("TestSupportOperation", false)
        , m_supported(true)
        , m_errorMsg()
        , m_version(1.3)
    {}

    virtual void operator() (osg::GraphicsContext* gc)
    {
        OpenThreads::ScopedLock<OpenThreads::Mutex> lock(m_mutex);
        osg::GLExtensions* gl2ext = gc->getState()->get<osg::GLExtensions>();

        if( gl2ext ){

            if( !gl2ext->isGlslSupported )
            {
            m_supported = false;
            m_errorMsg = "ERROR: GLSL not supported by OpenGL driver.";
            }
            else
                m_version = gl2ext->glVersion;
        }
        else{
            m_supported = false;
            m_errorMsg = "ERROR: GLSL not supported.";
        }
    }

    OpenThreads::Mutex  m_mutex;
    bool                m_supported;
    std::string         m_errorMsg;
    float               m_version;
};

int main(int, char**)
{
#ifdef _WIN32
    ::SetProcessDPIAware();
#endif

    osgViewer::Viewer viewer;
    viewer.setUpViewInWindow(100,100,OSG_WIDTH, OSG_HEIGHT);

    // openGL version:
    osg::ref_ptr<TestSupportOperation> so = new TestSupportOperation;
    viewer.setRealizeOperation(so.get());
    viewer.realize();

    if (so->m_supported)
        std::cout << "GLVersion=" << so->m_version << std::endl;
    else
        std::cout << so->m_errorMsg << std::endl;

    return viewer.run();
}