Path: utzoo!attcan!uunet!mcsun!ukc!slxsys!bae-st!mike
From: mike@ste.dyn.bae.co.uk (Mike Heley)
Newsgroups: comp.windows.open-look
Subject: Re: NeWS graphics in X11 program
Message-ID: <1991Jan23.103329.11656@ste.dyn.bae.co.uk>
Date: 23 Jan 91 10:33:29 GMT
Reply-To: mike@ste.dyn.bae.co.uk (Mike Heley)
Organization: British Aerospace (Dynamics), Stevenage
Lines: 49

In response to Steve Cole's request for advice on using NeWS graphics
from an X11 program -

I am in the process of changing the canvas graphics output portion of an
XView program from xlib to the NeWS extended postscript. Since I have most
of it working now, I can tell you where I started looking and a few of
the problems I found.

In my OpenWindows 2.0 there was a document ($OPENWINHOME/share/xvps.ps) which
describes the PSCANVAS package. I found the package itself pretty limited,
compared to the normal XView canvas, in particular, there seemed to be
no support for split views or event procs. My application also couldn't
cope with the fact that the repaint/resize procs got called with a changing
xview object handle.

However, there are a couple of cps macros which allow NeWS graphics on
any X11 window. I used these in combination with the normal XView canvas
object to get full canvas functionality + NeWS on the paintwindows.

I couldn't find the cps source file for the macros, but working back from the
tokenised macros, I found they do something like

#define CANVAS_TOKEN_TAG 51
cdef ps_token_from_xid(xid, canvastoken)
        => CANVAS_TOKEN_TAG (canvastoken)
        xid /XLookupID XResource send dup type
        /canvastype ne
        {pop -1}
        {currentfile countfileinputtoken dup 3 -2 roll setfileinputtoken}
        ifelse
        CANVAS_TOKEN_TAG tagprint
        typedprint

cdef ps_setcanvas(token canvastoken)
        canvastoken setcanvas

which seems to work okay.

One thing I would like to know. How do you go about debugging applications
which use cps macros, and how on earth to you handle error conditions
which occur on the server side?

--
  Mike Heley 					mike@ste.dyn.bae.co.uk
  British Aerospace Dynamics			+44 438 752432
  Stevenage, UK

  "Schizophrenic? I'm bleedin' Quadrophenic!" - The Who, 1973.
--