Conference bulova::decw_jan-89_to_nov-90

1011.0. "XCopyArea() Problem !!!" by GLORY::BENORE (Mike Benore, DTN 444-2107) Fri Jun 23 1989 15:18

	PROBLEM WITH XCopyArea()
        ======= ==== ===========

I have a customer, Wayne State University, who is developing 
X Windows based CAsE Software. They have been using Ultrix 
for a couple of years and started their work on X10 and have 
migrated it to X11, using a release from MIT running on 
ULTRIX V2.2. They now want to migrate their code to UWS 2.0 
and have one machine running UWS, but are having some 
problems with what they perceive differences in the MIT 
release from XUI. They won't migrate the rest of their 
machines to UWS 2.0, and have stalled on buying any 
DECstations until we can convince them that our X 
implementation will do the job, and they won't lose 
portability.

The biggest problem that they are having right now is with 
XCopyArea. The following is the note the customer sent with 
source code attached and comments that describe the problem. 
Any insights on this would be most appreciated, as their 
software package is quite nice and we would love to see it 
run under Ultrix as well as have them buy DECstations :-)

Thanks,

Mike Benore
usfhsl::benore

This program grabs a protion of the root window, and then 
copies that to the same area on the screen. It is not 
grabbing any pixels from inferior windows, and only paints a
solid window. hey want it to grab all the information in the
requested area, including inferior windows.

The customer confirmed agian today that this is the only 
thing holding them back from moving their software to UWS 
2.0.

Thanks again.

------------------------------------------------------------------------------
 
   In the process of upgrading from ULTRIX 2.2 to UWS 2.0 running 
DECwindows, we have encountered a problem with the X11 command XCopyArea
when it is used to copy a portion of the root window into a pixmap.
 
   This problem doesn't occur on our microVAX GPX running ULTRIX 2.2.
 
   Any suggestions can be e-mailed to [email protected] 
   or call at (313)577-0565 (ask for Brent or Nick)
 
   On the next page is a 30-line program which demonstrates the problem.
 
   Thank you for your help. 

/*  --  The following code demonstrates the problem we are having
    --  with XCopyArea with UWS 2.0.  Two carriage returns were added
    --  to separate the executions of XCopyArea.
*/
#include <stdio.h>
#include <X11/Xlib.h>
Display	  *dpy;      
GC	   gc; 
Pixmap     pix;      
Drawable   d;
XGCValues  values;
 
main()
{
  if ((dpy = XOpenDisplay("")) == 0)
  { printf("Cannot Open Display\n"); exit (1); }
 
  /*  --  When d is assigned to a window id created by our program,
      --  then this code works.
      --  The problem occurs when d is assigned the RootWindow.
  */
  d = RootWindow(dpy, DefaultScreen(dpy));
 
  if ((pix = XCreatePixmap (dpy, d, 100, 100, 
       DefaultDepth(dpy,DefaultScreen(dpy))))==0) printf("Can't Create pix\n");
  gc   = DefaultGC(dpy,  DefaultScreen(dpy));
 
  /* -- This is probably needed to copy from any windows on top of the
     -- Rootwindow(we tried it without it, it also fails)
   */ 
  XSetSubwindowMode( dpy, gc, IncludeInferiors );
  XFlush(dpy);
 
  /* -- Store screen area to pixmap
   */
  if(XCopyArea(dpy,d,pix,gc,0,0,100,100,0,0) == 0) printf("Root copy error\n");
  else printf("Root window copied to Pixmap.\n");
  XFlush(dpy);
  getchar();
 
  /* -- Put previously copied area back to the Rootwindow, at the same location
     -- (on our machine it throws garbage on the screen).
   */
  if(XCopyArea(dpy,pix,d,gc,0,0,100,100,0,0)==0) printf("Pix copy error\n");
  else printf("Pixmap copied to Root window.\n");
  XFlush(dpy);
  getchar();
}
 

This may not be the problem but, I thought applications are not supposed to
change the default graphics context.

Jatin

The program works fine on my PMAX (UWS 2.1)....but Ken Lee (WSL) found
the cause of the problem.

The same question had been posted to the USENET [comp.windows.x]

Kris...
-------

From: [email protected] (Ken Lee)
Subject: Re: XCopyArea Problem With UWS 2.0
Date: 23 Jun 89 21:35:40 GMT


In article <[email protected]>, [email protected] (Virtual Interactive
Programming) writes:
> In the process of upgrading from ULTRIX 2.2 to UWS 2.0 running
> DECwindows, we have encountered a problem with the X11 command XCopyArea
> when it is used to copy a portion of the root window into a pixmap.

Well, I ran your program as-is on a DECstation 3100 and a VAXstation 2000. 
Both worked perfectly.  Both were running ULTRIX UWS2.1 DECwindows 
(should be publicly available now), so you may want to upgrade.

I believe that your problem was a bug in the UWS2.0 X server.  Early MIT 
sample servers suffered from the same bug (copy area with IncludeInferiors).

Ken Lee
DEC Western Software Laboratory, Palo Alto, Calif.
Internet: [email protected]
Uucp: uunet!decwrl!klee

I cannot agree.

I'm running UWS 2.1 on a GPX and the problem is still there.

I figured out that this is not a problem of XCopyArea() nor one of the
server. The problem is caused by our window manager. If you kill dxwm 
everything works fine, even if you start uwm. 

Please see also note 1431 for further informations.

Guenter.