Test FrameBUffer On Ubuntu 10.10 i386 Cant Display ?

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#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/ioctl.h>

int main()
{
int fbfd = 0;
struct fb_var_screeninfo vinfo;
struct fb_fix_screeninfo finfo;
long int screensize = 0;
char *fbp = 0;
int x = 0, y = 0;
long int location = 0;

// Open the file for reading and writing
fbfd = open("/dev/fb0", O_RDWR);
if (fbfd == -1) {
perror("Error: cannot open framebuffer device");
exit(1);
}
printf("The framebuffer device was opened successfully.\n");

// Get fixed screen information
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) {
perror("Error reading fixed information");
exit(2);
}

// Get variable screen information
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) {
perror("Error reading variable information");
exit(3);
}

printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);

// Figure out the size of the screen in bytes
screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;

// Map the device to memory
fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,
fbfd, 0);
if ((int)fbp == -1)
{
perror("Error: failed to map framebuffer device to memory");
exit(4);
}
printf("The framebuffer device was mapped to memory successfully.\n");

x = 100; y = 100; // Where we are going to put the pixel

// Figure out where in memory to put the pixel
for (y = 100; y < 300; y++)
{
for (x = 100; x < 5000; x++)
{

location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length;
if (vinfo.bits_per_pixel == 32)
{
*(fbp + location) = 100; // Some blue
*(fbp + location + 1) = 15+(x-100)/2; // A little green
*(fbp + location + 2) = 200-(y-100)/5; // A lot of red
*(fbp + location + 3) = 0; // No transparency
}
else
{ //assume 16bpp
int b = 10;
int g = (x-100)/6; // A little green
int r = 31-(y-100)/16; // A lot of red
unsigned short int t = r<<11 | g << 5 | b;
*((unsigned short int*)(fbp + location)) = t;

}

}
munmap(fbp, screensize);
close(fbfd);
return 0;
}

}


the result return message Successfull but it dont display Pixel on Desktop, can you help me

http://ca8.upanh.com/16.291.20619245.Pk30/screenshot6.png