LinuxQuestions.org - How to make X program not abort when its window is closed/server killed?

- Programming (https://www.linuxquestions.org/questions/programming-9/)

- - How to make X program not abort when its window is closed/server killed? (https://www.linuxquestions.org/questions/programming-9/how-to-make-x-program-not-abort-when-its-window-is-closed-server-killed-782237/)

How to make X program not abort when its window is closed/server killed?

I try to run a simple Xlib program:

Code:

 /*

  Simple Xlib application drawing a box in a window.

  gcc input.c -o output -lX11

 */



 #include <X11/Xlib.h>

 #include <stdio.h>

 #include <stdlib.h>

 #include <string.h>



 int main(void) {

  Display *d;

  Window w;

  XEvent e;

  char *msg = "Hello, World!";

  int s;



                        /* open connection with the server */

  d = XOpenDisplay(NULL);

  if (d == NULL) {

    fprintf(stderr, "Cannot open display\n");

    exit(1);

  }



  s = DefaultScreen(d);



                        /* create window */

  w = XCreateSimpleWindow(d, RootWindow(d, s), 10, 10, 200, 200, 1,

                          BlackPixel(d, s), WhitePixel(d, s));



                        /* select kind of events we are interested in */

  XSelectInput(d, w, ExposureMask | KeyPressMask);



                        /* map (show) the window */

  XMapWindow(d, w);



                        /* event loop */

  while (1) {

    XNextEvent(d, &e);

                        /* draw or redraw the window */

    if (e.type == Expose) {

      XFillRectangle(d, w, DefaultGC(d, s), 20, 20, 10, 10);

      XDrawString(d, w, DefaultGC(d, s), 50, 50, msg, strlen(msg));

    }

                        /* exit on key press */

    if (e.type == KeyPress)

      break;

  }



                        /* close connection to server */

  XCloseDisplay(d);



  return 0;

 }

When i kill X server or close program's window, it aborts with error:

Quote:

XIO: fatal IO error 11 (Resource temporarily unavailable) on X server ":0.0"
after 9 requests (9 known processed) with 0 events remaining.

I found that XNextEvent is the reason of abort.
How can i make it try to reconnect to new server or do anything else instead of just aborting?

Hi -

This thread might be useful to you:

http://www.linuxquestions.org/questi...IOErrorHandler

Search for "XSetIOErrorHandler" or "WM_DELETE_WINDOW".

'Hope that helps .. PSM

Quote:

Xlib calls the program's supplied error handler if any sort of system call error occurs (for example, the connection to the server was lost). This is assumed to be a fatal condition, and the called routine should not return. If the I/O error handler does return, the client process exits.

So, how should the program continue execution if it doesn't assume i/o error as fatal? goto some label in main()? But then there's a memory leak at least in stack... is there a better way?

Hi -

If you want to mess around with Xlib, you get to manage the low level details yourself.

If you wanted to try a higher-level framework (which, of course, I strongly encourage), then the framework will probably let you handle things like "window manager close" events more easily. You might want to investigate either/both GTK+ and/or Qt.

IMHO .. PSM