Hello everyone , i enter in this forum because i don't get how to use this extension correctly, i have this code and only i get a white texture, i'm trying to get a texture from a window or the entire desktop of my ubuntu and showing it in a GLUT window, but in both cases i get a white texture without errors, this is my code:

Code :
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/extensions/Xcomposite.h>
#include <X11/extensions/Xfixes.h>
#include<GL/gl.h>
#include<GL/glx.h>
#include <GL/glext.h>
#include<GL/glu.h>
#include <GL/glut.h>
 
static PFNGLXBINDTEXIMAGEEXTPROC glXBindTexImageEXT = NULL;
static PFNGLXRELEASETEXIMAGEEXTPROC glXReleaseTexImageEXT = NULL;
 
Display  *display;
Window window;
int value;
float top,bottom;
int nfbconfigs;
GLuint texture;
int i;
GLXFBConfig *fbconfigs;
 
Window getWindowIdFromName(Display *dpy, Window level, char *name)
{
    Window *children;
    Window dmy;
    Window root;
    Window id;
    char *window_name;
    int i;
    unsigned int no_of_children;
 
    if (0 == XQueryTree(dpy, level, &dmy, &dmy, &children, &no_of_children))
        return 0;
 
    for (i=0; i<no_of_children; i++)
    {
        if (XFetchName(dpy,children[i], &window_name))
        {
            if (strcmp (name, window_name))
                XFree(window_name);
            else
            {
                XFree(window_name);
                return children[i];
            }
        }
        else
        {
            if (id = getWindowIdFromName(dpy, children[i], name))
                return id;
        }
    }
    return 0;
}
 
void drawing(){
    //sleep(1);
 
 
        /* draw using pixmap as texture */
    glClearColor(0.25, 0.25, 0.25, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);
    glPushMatrix();
 
        glBegin (GL_QUADS);
    glVertex3f(-1.0f,1.0f,0.0f);
    glTexCoord2d(-1.0f,1.0f);
    glVertex3f(1.0f,1.0f,0.0f);
    glTexCoord2d(1.0f,1.0f);
    glVertex3f(1.0f,-1.0f,0.0f);
    glTexCoord2d(1.0f,-1.0f);
    glVertex3f(-1.0f,-1.0f,0.0f);
    glTexCoord2d(-1.0f,-1.0f);
 
        glEnd ();
    glPopMatrix();
    glutSwapBuffers();
}
 
 
int main(int argc, char **argv){
 
 
 
    glutInit(&argc,argv);
//glutInitDisplayMode (GLUT_SINGLE | GLUT_RGBA);
 
      glutInitWindowPosition(0,0);
 
      glXBindTexImageEXT = (PFNGLXBINDTEXIMAGEEXTPROC)
          glXGetProcAddress((GLubyte *) "glXBindTexImageEXT");
       glXReleaseTexImageEXT = (PFNGLXRELEASETEXIMAGEEXTPROC)
          glXGetProcAddress((GLubyte*) "glXReleaseTexImageEXT");
 
       if(!glXBindTexImageEXT || !glXReleaseTexImageEXT)
           {
               printf("Some extension functions missing!\n");
               //return 1;
         }
 
    display = XOpenDisplay(NULL);
    window = XDefaultRootWindow(display);
    XCompositeRedirectSubwindows (display, window, CompositeRedirectAutomatic);
    XSelectInput (display, window, SubstructureNotifyMask);
    XWindowAttributes attrib;
    XGetWindowAttributes (display, window, &attrib);
 
        VisualID visualid = XVisualIDFromVisual (attrib.visual);
 
        fbconfigs = glXGetFBConfigs (display, XDefaultScreen(display), &nfbconfigs);
        for (i = 0; i < nfbconfigs; i++)
        {
            XVisualInfo *visinfo = glXGetVisualFromFBConfig (display, fbconfigs[i]);
            if (!visinfo || visinfo->visualid != visualid)
                continue;
 
            glXGetFBConfigAttrib (display, fbconfigs[i], GLX_DRAWABLE_TYPE, &value);
            if (!(value & GLX_PIXMAP_BIT))
                continue;
 
            glXGetFBConfigAttrib (display, fbconfigs[i],
                                  GLX_BIND_TO_TEXTURE_TARGETS_EXT,
                                  &value);
            if (!(value & GLX_TEXTURE_2D_BIT_EXT))
                continue;
 
            glXGetFBConfigAttrib (display, fbconfigs[i],
                                  GLX_BIND_TO_TEXTURE_RGBA_EXT,
                                  &value);
            if (value == False)
            {
                glXGetFBConfigAttrib (display, fbconfigs[i],
                                      GLX_BIND_TO_TEXTURE_RGB_EXT,
                                      &value);
                if (value == False)
                    continue;
            }
 
            glXGetFBConfigAttrib (display, fbconfigs[i],
                                  GLX_Y_INVERTED_EXT,
                                  &value);
            if (value == True)
            {
                top = 0.0f;
                bottom = 1.0f;
            }
            else
            {
                top = 1.0f;
                bottom = 0.0f;
            }
 
            break;
        }
 
        if (i == nfbconfigs){
            /* error 1 */
        printf("error \n");
    }
 
    //Window wind = getWindowIdFromName(display,window,"Qt");
    Pixmap pixmap = XCompositeNameWindowPixmap (display, window);
        const int pixmapAttribs[] = { GLX_TEXTURE_TARGET_EXT, GLX_TEXTURE_2D_EXT,
                          GLX_TEXTURE_FORMAT_EXT, GLX_TEXTURE_FORMAT_RGBA_EXT,
              GLX_MIPMAP_TEXTURE_EXT,
                          None };
        GLXPixmap glxpixmap = glXCreatePixmap (display, fbconfigs[i], pixmap, pixmapAttribs);
 
    gluOrtho2D(0,attrib.width,0,attrib.height);
        glEnable(GL_TEXTURE_2D);
        glGenTextures (1, &texture);
        glBindTexture (GL_TEXTURE_2D, texture);
    //XGrabServer(display);
    printf("drawing pixmap \n");   
        glXBindTexImageEXT (display, glxpixmap, GLX_FRONT_LEFT_EXT, NULL);
        printf("pixmap binded\n");
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    //XUngrabServer(display);
    //glXReleaseTexImageEXT (display,glxpixmap,GLX_FRONT_LEFT_EXT);
        glutInitWindowSize(500,500);
        glutCreateWindow("simplex");
 
    glutDisplayFunc(drawing);
    //glutIdleFunc(drawing);
 
 
    glutMainLoop();
        return 0;
}

any helps i will appreciate it so much, i wasted a lot of time with this...