problem in xlib programming

[hamedhsn]

i wrote a program,it is an xlib program..
i want to catch the event regarding to a window like firefox that is running on the server and i got this error:

X Error of failed request: BadAccess (attempt to access private resource denied)
Major opcode of failed request: 2 (X_ChangeWindowAttributes)
Serial number of failed request: 11
Current serial number in output stream: 13


when i add this line to the code ,error occured:

XSelectInput (display, w, ExposureMask | KeyPressMask | ButtonPressMask);

this is a part of code:

Window rt,pr;
Window *children_return;
unsigned int nofch;
int f=XQueryTree(display, DefaultRootWindow(display), &rt, &pr, &children_return, &nofch);
uint *array=(uint*)children_return;
uint k;
for (k = 0; k < nofch; k++)
{
//GET THE STATUS OF WINDOW
XWindowAttributes a;
XGetWindowAttributes(display, children_return[k], &a);
//printf("status:%d",a.map_state);

//GET THE WINDOW ID:
Window w = (Window) array[k];
char * name='\0';
int status =XFetchName(display,w,&name);
if (status>=Success&&a.map_state==2)
{
printf("Found %u: %u %s -- statuse=%d\n",k, w, name,a.map_state);
XSelectInput (display, w, ExposureMask | KeyPressMask | ButtonPressMask);
}
}

[Rubberman]

Are you running the xlib program in the same user account as Firefox? On the same machine where Firefox is being run (client machine), or (if they are different) on the X display server machine? You may need to make sure that your X display is the same as Firefox, and it is possible that you may need to run the xlib application as root in order to overcome the privacy/permissions issue that you have run into.

[hamedhsn]

Are you running the xlib program in the same user account as Firefox? On the same machine where Firefox is being run (client machine), or (if they are different) on the X display server machine? You may need to make sure that your X display is the same as Firefox, and it is possible that you may need to run the xlib application as root in order to overcome the privacy/permissions issue that you have run into.

yes,it is running on single computer..
also i run it as root...

but i dont know how i can check weather X display is the same as Firefox or not??
i create' display' in my program by this command "display = XOpenDisplay (0); ".

[Rubberman]

The display is either set via the DISPLAY environment variable, or a command-line option to the program which in turn sets the DISPLAY environment inside the application. Normall this would be :0.0