/**********************************************************************
 * To compile:
 *  gcc -o simple-x simple-x.c -lm -lXm -lXt -lX11
 *
 * Usage:  simple-x -bg white -fg black -geometry 300x300+10+10
 *
 * From another window you may run xv which allows you to grab your simple-x
 * window and print it or save it in some other format.
 **********************************************************************/

#include <Xm/Xm.h>
#include <Xm/DrawingA.h>

void redraw(Widget w, XtPointer client_data, XtPointer call_data);

main(int argc, char *argv[])
{
  XtAppContext	  app_context;
  Widget          toplevel, canvas;
  GC              gc;
  XColor          color;
  XGCValues       values;
  Arg		  wargs[2];
  int		  n;

  /* Create the top level window shell */

  toplevel = XtAppInitialize(&app_context,argv[0], NULL, 0, &argc, argv,
			     NULL, NULL, 0);

  /* Create the drawing area widget within the toplevel shell. */

  n = 0;
  XtSetArg(wargs[n], XmNwidth, 300); n++;
  XtSetArg(wargs[n], XmNheight, 300); n++;
  canvas = XtCreateManagedWidget("canvas", xmDrawingAreaWidgetClass,
				   toplevel,wargs,n);
  /*
   * Create a gc to draw with.  Make sure it's foreground color is the
   * default foreground color of the widget, so it can be changed on the
   * command line.
   */

  n = 0;
  XtSetArg(wargs[n], XmNforeground, &(color.pixel)); n++;
  XtGetValues(canvas, wargs, n);
  values.foreground = color.pixel;

  gc = XCreateGC(XtDisplay(canvas), DefaultRootWindow(XtDisplay(canvas)),
		 GCForeground, &values);

  /* Tell X the name of the function that redraws the picture. */

  XtAddCallback(canvas, XmNexposeCallback, redraw, gc);

  /* Make the widget real. */

  XtRealizeWidget(toplevel);

  /* Enter the infinite loop for processing X events. */

  XtAppMainLoop(app_context);
}





/**********************************************************************
 * This function draws the whole figure.  It is called anytime the
 * window needs to be redrawn.
 **********************************************************************/

void redraw(Widget w, XtPointer client_data, XtPointer call_data)
{
  int   i;
  GC gc;

  gc = (GC)client_data;

  for (i = 10; i < 200; i++)
    XDrawPoint(XtDisplay(w), XtWindow(w), gc, i, i);

  for (i = 10; i < 200; i++)
    XDrawPoint(XtDisplay(w), XtWindow(w), gc, 210-i, i);

}