Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!warwick!csuyk
From: csuyk@warwick.ac.uk (FUNG Wai Wa)
Newsgroups: comp.windows.x
Subject: Help! What is the magic of the sleep() statement?
Message-ID: <1991Jan9.150326.6248@warwick.ac.uk>
Date: 9 Jan 91 15:03:26 GMT
Sender: news@warwick.ac.uk (Network news)
Organization: Computing Services, Warwick University, UK
Lines: 76


Hi, there,

I am new to Xlib programming. I am now stuck at a very funny(?) problem
that I can't solve. Would any Xlib expert give me a hand? Thanks.

The following few statements attempt to create a window and draw a line
with some strings. I found that the sleep(1) statement is very crucial
for its success. Its presence can make the program work as I expect but
its absence make the program map the windows only. No drawing at all, if
I run this program from another machine. Occasionally I can get it running
in the same workstation where I started X.

Would any guru give me some hints to get around  this nasty problem?


Regards,
FUNG W.W.


----cut here
#include <stdio.h>
#include <X11/Xlib.h>

main()
{
    Display              *dpy;
    int                  scr;
    Window               win;
    GC                   gc;

    XGCValues            gcvalues;
    XSetWindowAttributes attributes;
    Visual               *visual = CopyFromParent;

    dpy = XOpenDisplay(NULL);     /* connect to the default display */
    if (dpy != (Display*)NULL)
        scr = DefaultScreen(dpy);
    else {
        printf("Cannot connect to server\n");
        exit(0);
    }

    /* creating a very simple window */
    attributes.background_pixel = BlackPixel(dpy, scr);
    win = XCreateWindow(dpy, RootWindow(dpy, scr),
                        100, 100, 500, 500, 1,
                        CopyFromParent,
                        InputOutput,
                        visual,
                        CWBackPixel, &attributes);
    XMapRaised(dpy, win);
    XFlush(dpy);

    /* create the pen */
    gcvalues.foreground = WhitePixel(dpy, scr);
    gc = XCreateGC(dpy, win, GCForeground, &gcvalues);

    /* nasty stmt that its existence is crucial
       if this stmt is omitted, there is chance to get the program
           working in the same workstation that I started X. However,
           if I compile and execute this program in another machine
           over the network, only a blank window appeared but no
           drawing will be done.
       However, with this sleep stmt, everything OK. Why???
    */
    sleep(1);

    XDrawLine(dpy, win, gc, 0, 0, 300, 300);
    XDrawString(dpy, win, gc, 100, 100, "Xlib", 4);
    XDrawString(dpy, win, gc, 200, 200, "Hello", 5);
    XDrawString(dpy, win, gc, 300, 300, "Xlib", 4);
    XFlush(dpy);

    while (1);
}