Example Program Listing

/* win.c --- a very basic Xlib application, Jeff Pitchers, LUT 1993 */

/* The basic set of header files for any Xlib program */
#include <stdio.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xresource.h>
#include <X11/keysym.h>

Display *display;  /* Server or display to which a connection will be made */
int screen;        /* Screen number to use on that display */
Window win;        /* The applications one and only window */
XEvent event;      /* The event data structure */
GC gc1, gc2;       /* Graphics context data structures */
XGCValues gs1,gs2; /* Graphics context settings */
char *message;     /* Message printed in window */
static char progDefaultMessage[] = {"A Simple Xlib Program"};

main(argc, argv)
int argc; char **argv;
{
  /* Attempt to connect to the server and use the default screen */
  if ((display = XOpenDisplay(NULL)) == NULL) {
    perror("Can't connect to server");
    exit(1);
  }
  screen = DefaultScreen(display);

  /* Create a window */
  win = XCreateSimpleWindow(display, RootWindow(display, screen),
          100, 200, 400, 300, 1, BlackPixel(display, screen),
          WhitePixel(display, screen));

  /* Set up which event types the window will handle */
  XSelectInput(display, win, ExposureMask | ButtonPressMask);

  /* Graphics contexts */
  setUpGCs();

  /* Attempt to get message from user-defined resource setting */
  if ((message = XGetDefault(display, "win", "message")) == NULL)
    message = progDefaultMessage;

  /* Map the window in order for it to be displayed */
  XMapWindow(display, win);

  /* Enter an infinite loop, awaiting and responding to the chosen events */
  while (1) {
    XNextEvent(display, &event);
    switch (event.type) {
      case Expose: drawInToWindow(); break; /* Draw/re-draw everything */
      case ButtonPress: exit(0); break; /* Quit on mouse button press */
      default: break;
    }
  }
}

setUpGCs()
/* Set up 2 graphics context resources in the display server */
/* gc1 for message and rectangle; gc2 for ellipse */
{
/* Define a bitmap for the stipple pattern used to fill the ellipse */
#define stipple_width 3
#define stipple_height 3
  static char stipple_bits[] = {0x02, 0x05, 0x02};
  Pixmap stipple;

  /* Create the stipple for ellipse fill pattern of gc2 */
  if ((stipple = XCreateBitmapFromData(display, RootWindow(display, screen),
    stipple_bits, stipple_width, stipple_height)) == 0) {
    perror("Can't create bitmap");
    exit(1);
  }

  gc1 = XCreateGC(display, win, 0, &gs1); /* 0 -> use defaults */
  gc2 = XCreateGC(display, win, 0, &gs2); /* 0 -> use defaults */
  /* Now override some of the defaults */
  XSetForeground(display, gc1, BlackPixel(display, screen));
  XSetBackground(display, gc1, WhitePixel(display, screen));
  XSetLineAttributes(display, gc1, 2, LineSolid, CapRound, JoinRound);
  XSetStipple(display, gc2, stipple);
  XSetFillStyle(display, gc2, FillOpaqueStippled);
}

drawInToWindow()
{
  /* Print message, draw restangle and filled ellipse as defined */
  /* by the GC */
  XDrawString(display, win, gc1, 130, 20, message, strlen(message));
  XDrawRectangle(display, win, gc1, 40, 40, 320, 220);
  XFillArc(display, win, gc2, 50, 50, 300, 200, 0, 360*64);
}

 
Figure 16: Result of running the example program