Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!bloom-beacon!MANATEE.CIS.UFL.EDU!kml
From: kml@MANATEE.CIS.UFL.EDU (Kevin Lahey)
Newsgroups: comp.windows.x
Subject: Re: XPutImage monochrome image to color screen (sample program)
Message-ID: <8904261720.AA00608@manatee.cis.ufl.edu>
Date: 26 Apr 89 17:20:41 GMT
Sender: daemon@bloom-beacon.MIT.EDU
Organization: The Internet
Lines: 123

/*
 * A sample program to demonstrate my XPutImage problems.  This program is
 * written using Xt, but I got the same sort of error when I used XPutImage
 * with just strictly X programming;  i.e., I don't think it is a
 * toolkit problem. 
 *
 * The problem:  the program has no trouble displaying on a monochrome screen,
 * but on a color screen, I get strange results:  the image is displayed
 * correctly, completely, but as soon as it is displayed, a vertical white
 * band is drawn on the image.  This doesn't happen every time, but mostly
 * when I change the horizontal dimensions of the window, either with the
 * scroll bars or by changing the size of the window from the window manager.
 *
 * I'm running SunOS 4.0 on Sun3s and X11R3 with Purdue speedups.
 * I tried to make this example program minimalistic while still
 * retaining the same behavior as my program.  With luck, I just missed
 * something subtle, and this isn't an X problem, although the program xim
 * hinted at this problem in the README and xviewsun contains a workaround,
 * but no comments.
 *
 * I appreciate mailed as well as posted responces:
 * Kevin Lahey                  UUCP: ...gatech!uflorida!beach.cis.ufl.edu!kml
 * University of Florida, CIS   Internet: kml@beach.cis.ufl.edu
 */

#include <X11/Intrinsic.h>
#include <X11/StringDefs.h>
#include <X11/Shell.h>
#include <X11/Core.h>
#include <X11/Viewport.h>

void	event_proc ();

Display	*display;
Widget	shell,
	view,
	canvas;
XImage	*image;

main (argc, argv)
int	argc;
char	**argv;
{
	int			width = 400, height = 500;
	XWindowAttributes	window_attributes;
	XtAppContext		app_context;
	Arg			arg_list [4];

	XtSetArg(arg_list [0], XtNwidth, 200);
	XtSetArg(arg_list [1], XtNheight, 200);
	XtSetArg(arg_list [2], XtNallowVert, True);
	XtSetArg(arg_list [3], XtNallowHoriz, True);

	XtToolkitInitialize ();
	app_context = XtCreateApplicationContext ();
	display = XtOpenDisplay (app_context, NULL, "Sample", "xdemo",
				 NULL, 0, &argc, argv);
	shell = XtAppCreateShell ("Sample", "xdemo", 
				  applicationShellWidgetClass, 
				  display, NULL, 0);

	view = XtCreateManagedWidget ("view", viewportWidgetClass,
				      shell, arg_list, 4); 
	XtSetArg(arg_list [0], XtNwidth, width);
	XtSetArg(arg_list [1], XtNheight, height);
	canvas = XtCreateManagedWidget ("canvas", widgetClass,
					view, arg_list, 2);
	
	XtAddEventHandler (canvas, ExposureMask, False, event_proc, 0);
	XtRealizeWidget (shell);

	create_image (width, height);

	XtAppMainLoop (app_context);
}


/*
 * Create a quick and dirty sample image for display.
 */

create_image (width, height)
int	width, height;
{
	int	i,
		bytes_wide;
	char	*data;

	data = (char *) malloc (width * height);

	for (i = 0; i < width / 8; i++)
		data [i] = 204;
	for (i = 0; i < width / 8; i++)
		data [i + width / 8] = 51;
	for (i = 0; i < height / 2; i++)
		bcopy (data, data + i * width / 4, width / 4);

	image = XCreateImage (display, 
			      XDefaultVisualOfScreen(XtScreen(canvas)),
			      1, XYBitmap, 0, data, width, height,
			      8, width / 8);

}

/*
 * Handle the exposure event.
 */

void
event_proc (w, client_data, event)
Widget	w;
caddr_t	client_data;
XExposeEvent	*event;
{
	if (event->type == Expose) {
		printf ("At X = %d Y = %d width = %d height = %d\n",
			event->x, event->y, event->width, event->height);
		XPutImage (display, XtWindow(w), 
			   XDefaultGCOfScreen (XtScreen(canvas)),
			   image, event->x, event->y, event->x, event->y, 
			   event->width, event->height);
	}
}