problems with drawing in x using xlib

Applications Programming
1

Hi all,

I'm currently learning xlib and I've encountered a bizarre mistake: function calls such as XDrawPoint, XDrawLine, etc., don't seem to work; a blank window with nothing in is appears. I believe this has something to do with the window manager I use, fluxbox.

After checking the code and not finding any mistakes, I decided to copy the code here - http://tronche.com/gui/x/xlib-tutorial/prog-2.cc - to see if it would work. Here it is:

#include <X11/Xlib.h> // Every Xlib program must include this
#include <assert.h>   // I include this to test return values the lazy way
#include <unistd.h>   // So we got the profile for 10 seconds

#define NIL (0)       // A name for the void pointer

main()
{
      // Open the display

      Display *dpy = XOpenDisplay(NIL);
      assert(dpy);

      // Get some colors

      int blackColor = BlackPixel(dpy, DefaultScreen(dpy));
      int whiteColor = WhitePixel(dpy, DefaultScreen(dpy));

      // Create the window

      Window w = XCreateSimpleWindow(dpy, DefaultRootWindow(dpy), 0, 0, 
                     200, 100, 0, blackColor, blackColor);

      // We want to get MapNotify events

      XSelectInput(dpy, w, StructureNotifyMask);

      // "Map" the window (that is, make it appear on the screen)

      XMapWindow(dpy, w);

      // Create a "Graphics Context"

      GC gc = XCreateGC(dpy, w, 0, NIL);

      // Tell the GC we draw using the white color

      XSetForeground(dpy, gc, whiteColor);

      // Wait for the MapNotify event

      for(;;) {
        XEvent e;
        XNextEvent(dpy, &e);
        if (e.type == MapNotify)
          break;
      }

      // Draw the line
      
      XDrawLine(dpy, w, gc, 10, 60, 180, 20);

      // Send the "DrawLine" request to the server

      XFlush(dpy);

      // Wait for 10 seconds

      sleep(10);
}

this is indeed completely plagiarized. Funnily though, it works (displays the white line) by starting x without fluxbox, i.e. an .xinitrc file like this:

"program-name"     #first do the program
startfluxbox           #then start fluxbox

this seems very bizarre and to be honest, I'm a bit lost...are there any settings I've not set?
Any help would be greatly appreciated.

Thanks in advance.