如何在NVidia Desktop上创建EGL上下文

Question

I'm looking for a code snipet to create EGL context on desktop NVidia.

I'm aware that on Windows, NVidia exposes EGL through extensions WGL_EXT_create_context_es_profile and WGL_EXT_create_context_es2_profile .

And on Linux NVidia allows EGL through GLX_EXT_create_context_es_profile and GLX_EXT_create_context_es2_profile extensions.

But I was unable to find an example, or sample code, to get it running.

Answer 1

after some struggle, I've got something like below.

The basic thing is to get required extensions, by hand or using GLEW, create dummy context and then create your GL-ES context. Error handling is omitted for clearance.

/**
 * adapted from
 * from https://www.opengl.org/wiki/Tutorial:_OpenGL_3.1_The_First_Triangle_%28C%2B%2B/Win%29
 */
bool CGLRenderer::CreateGLContext(CDC* pDC){
PIXELFORMATDESCRIPTOR pfd =
{
 sizeof(PIXELFORMATDESCRIPTOR),
1,
PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,    //Flags
PFD_TYPE_RGBA,            //The kind of framebuffer. RGBA or palette.
32,                        //Colordepth of the framebuffer.
0, 0, 0, 0, 0, 0,
0,
0,
0,
0, 0, 0, 0,
24,                        //Number of bits for the depthbuffer
8,                        //Number of bits for the stencilbuffer
0,                        //Number of Aux buffers in the framebuffer.
PFD_MAIN_PLANE,
0,
0, 0, 0
};  

int nPixelFormat = ChoosePixelFormat(pDC->m_hDC, &pfd); 
if (nPixelFormat == 0) return false;

BOOL bResult = SetPixelFormat (pDC->m_hDC, nPixelFormat, &pfd); 
if (!bResult) return false; 

HGLRC tempContext = wglCreateContext(pDC->m_hDC);
wglMakeCurrent(pDC->m_hDC, tempContext);

// Using GLEW. Init it after ctx creation
GLenum err = glewInit();
if (GLEW_OK != err){
    AfxMessageBox(_T("GLEW is not initialized!"));
}

// create OPENGL ES 2 profile. It may return a compatible, but higher GL-ES, as 3.0 or 3.1 
int attribList[] = {
            WGL_CONTEXT_MAJOR_VERSION_ARB, 2,
            WGL_CONTEXT_MINOR_VERSION_ARB, 0,
            WGL_CONTEXT_PROFILE_MASK_ARB, WGL_CONTEXT_ES2_PROFILE_BIT_EXT,
            0,
};

if(wglewIsSupported("WGL_ARB_create_context") == 1){
    m_hrc = wglCreateContextAttribsARB(pDC->m_hDC,0, attribs);
    wglMakeCurrent(NULL,NULL);
    wglDeleteContext(tempContext);
    wglMakeCurrent(pDC->m_hDC, m_hrc);
}else{  //Failed to create a GL-ES context. 
    m_hrc = NULL;
}

//Debug info - print out GL version 
const GLubyte *glVersionString = glGetString(GL_VERSION); 
const char *vendorChar = (char*)glGetString(GL_VENDOR);
const char *rendererChar = (char*)glGetString(GL_RENDERER);

int glVersion[2] = {-1,-1};
glGetIntegerv(GL_MAJOR_VERSION,&glVersion[0]);
glGetIntegerv(GL_MINOR_VERSION,&glVersion[1]);

cout<<"GL version string: "<< glVersionString << <<endl;
cout<<"OpenGL version: "<<glVersion[0]<<"."<<glVersion[1]<<endl;
cout<<"GPU: "<<vendorChar<<" - "<<rendererChar<<endl;

if (!m_hrc) return false;

return true;
} // end of CreateGLContext