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From: tuceryan@mohawk.cps.msu.edu (Mihran Tuceryan)
Newsgroups: comp.windows.x
Subject: What am I doing wrong?
Message-ID: <1991Jan20.215551.15000@msuinfo.cl.msu.edu>
Date: 20 Jan 91 21:55:51 GMT
Sender: news@msuinfo.cl.msu.edu
Reply-To: tuceryan@mohawk.cps.msu.edu (Mihran Tuceryan)
Organization: PRIP Lab, Comp. Sci. Dept., MSU
Lines: 63

The following is supposed to be a simple test program that draws a straight
line in a window. The window appears but nothing is drawn. What is wrong with
this program? Any help is appreciated. (the display is 8 bits deep and
this is using Xw widgets).

Mihran Tuceryan
email: tuceryan@cps.msu.edu

/*************************************************
 * xy.c: Draw a line from (x1,y1) to (x2,y2).
 *************************************************/
#include <X11/Intrinsic.h>
#include <X11/StringDefs.h>
#include <Xw/Xw.h>
#include <Xw/WorkSpace.h>

 main(argc, argv)
	int     argc;
	char    *argv[];
 {
	int       x1, y1, x2, y2;
	Widget    toplevel, canvas;
        GC        gc;
        XGCValues gcv;
	Display	  *dpy;
	Window    win;
        Arg       args[10];
        int       n = 0;
      
	/*  Initialize the Intrinsincs */
        toplevel = XtInitialize (argv[0], "SATCS", NULL, 0,
				 &argc, argv);

	dpy = XtDisplay(toplevel);
        /*  Create the workspace widget.  */
        canvas = XtCreateManagedWidget ("canvas",
					XwworkSpaceWidgetClass,
					toplevel, NULL, 0);
        /* Alter widget size (p 23) */
	n = 0;
        XtSetArg (args[n], XtNwidth, 400); n++;
        XtSetArg (args[n], XtNheight, 400); n++;
	XtSetArg (args[n], XtNforeground, WhitePixel(dpy, DefaultScreen(dpy))); n++;
	XtSetArg (args[n], XtNbackground, BlackPixel(dpy, DefaultScreen(dpy))); n++;
        XtSetValues (canvas, args, n);
        /*  Realize the widgets  */
        XtRealizeWidget (toplevel);

	win = XtWindow(canvas);
        gcv.background = BlackPixel(dpy, DefaultScreen(dpy));
        gcv.foreground = WhitePixel(dpy, DefaultScreen(dpy));
	gcv.line_style = LineSolid;
	gcv.function = GXcopy;
	gc = XtGetGC(canvas, 
		     GCFunction |
		     GCForeground | GCBackground |
		     GCLineStyle,
		     &gcv);
	x1 = 50; y1 = 50;
	x2 = 100; y2 = 100;
	XDrawLine(dpy, win, gc, x1, y1, x2, y2);
        XtMainLoop ();
 }