Path: utzoo!attcan!uunet!steinmetz!nepal!laymon
From: laymon@nepal.steinmetz (Marc A Laymon)
Newsgroups: comp.windows.x
Subject: rubber banding in X
Message-ID: <10979@steinmetz.ge.com>
Date: 24 May 88 18:35:29 GMT
Sender: news@steinmetz.ge.com
Reply-To: laymon@nepal.steinmetz ()
Distribution: na
Organization: General Electric CRD, Schenectady, NY
Lines: 54

Question #1:

I want to draw a rubber-banding line.  It would seem to me that I want
to repeatedly draw a line in exclusive-or mode.  I tried to use the
following code fragment (and several variations thereof) to try to set
the graphics context to exclusive-or, then call XDrawLine using the
graphics context.  My line does not show up.  Can someone tell me what
I am doing wrong or suggest another approach ?  

----------------------------------------------------------------------------
    Display 	*dpy ;
    int     g_black ;
    int     g_white ;
    unsigned long    mask ;
    GC	  xor_gc ;
    XGCValues    xgcv ;

    g_black = BlackPixel (dpy, screen);
    g_white = WhitePixel (dpy, screen);
    mask = g_black ^ g_white ;

    xgcv.foreground = mask ;
    xgcv.background = g_white ;
    xgcv.line_width = 1 ;
    xgcv.function = GXxor ;

    gc_mask = 0 ;
    gc_mask = GCFunction | GCPlaneMask | GCForeground | GCBackground | GCLineWidth ;

    xor_gc = XCreateGC (dpy, Rootwindow, GCFunction, &xgcv) ;

    while (*whatever*)
    {
	[code to modify x[1] & y[1]]
	XDrawLine (dpy, Rootwindow, xor_gc, x[0], y[0], x[1], y[1]) ;
    }

--------------------------------------------------------------------------

Question #2

I created a graphic widget using the X Intrinsics.  This widget is just
a blank window into which I can use Xlib graphics functions.  This works
fine.  However, if my base window containing this graphic widget is
resized or moved via the window manager, I lose the contents of the window.  
Is there an easy way to preserve and restore the random contents of a window ?
Regions or buffers don't seem to be what I want.

Thanks in advance.


 Marc Laymon			ARPANET: laymon@ge-crd.arpa
 GE Corp. R&D			USENET:  steinmetz!nepal!laymon
 Schenectady, NY