Ubuntu Linux下通过c++获取屏幕大小

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <math.h>
int w,h ,bpp;
int *fbmem;
int main(int argc , char *argv[]){
int fd;
struct fb_var_screeninfo fb_var;
fd = open("/dev/fb0",O_RDWR);
ioctl (fd,FBIOGET_VSCREENINFO,&fb_var);
w = fb_var.xres;
h = fb_var.yres;
bpp = fb_var.bits_per_pixel;
printf ("Framebuffer %d*%d-%dbpp\n",w,h,bpp);
fbmem = mmap (0,w*h*bpp/8,PROT_WRITE|PROT_READ,
MAP_SHARED,fd,0);
return 0；
} 

#include <stdio.h>
#include <xcb/xcb.h>
int  main (){
        /* Open the connection to the X server. Use the DISPLAY environment variable */
 
        int i, screenNum;
        xcb_connection_t *connection = xcb_connect (NULL, &screenNum);

        /* Get the screen whose number is screenNum */ 
        const xcb_setup_t *setup = xcb_get_setup (connection);
        xcb_screen_iterator_t iter = xcb_setup_roots_iterator (setup);  

        // we want the screen at index screenNum of the iterator
        for (i = 0; i < screenNum; ++i) {
            xcb_screen_next (&iter);
        }
 
        xcb_screen_t *screen = iter.data;
 
        /* report */
        printf ("\n");
        printf ("Informations of screen %ld:\n", screen->root);
        printf ("  width.........: %d\n", screen->width_in_pixels);
        printf ("  height........: %d\n", screen->height_in_pixels);
        printf ("  white pixel...: %ld\n", screen->white_pixel);
        printf ("  black pixel...: %ld\n", screen->black_pixel);
        printf ("\n");
 
        return 0;
    }