Path: utzoo!attcan!uunet!mcsun!unido!pcsbst!jkh
From: jkh@meepmeep.pcs.com (Jordan K. Hubbard)
Newsgroups: comp.windows.x
Subject: Re: Athena asciiStringWidget questions
Message-ID: <JKH.89Oct28161254@meepmeep.pcs.com>
Date: 28 Oct 89 16:12:54 GMT
References: <8909252128.AA28066@mbunix.mitre.org>
	<8910262127.AA20276@expo.lcs.mit.edu>
Sender: news@pcsbst.UUCP
Organization: PCS Computer Systems, GmbH
Lines: 52
In-reply-to: kit@EXPO.LCS.MIT.EDU's message of 26 Oct 89 21:27:39 GMT

This brings up a question I have about the asciiStringWidget, perhaps
Chris can help me too. I have an application (the Info browsing widget, for
the curious) that uses an ascii string widget to display a section of
text from a large allocated chunk of memory. The text widget's "window"
into this chunk of memory (and often the chunk of memory itself) changes
frequently. This is what I did:

     XtTextSource oldSource, newSource;

..

     oldSource = XtTextGetSource(widget);

     i = 0;
     XtSetArg(args[i], XtNlength, .. new length ..);			i++;
     XtSetArg(args[i], XtNstring, .. new start ptr in buffer ..);	i++;
     XtSetArg(args[i], XtNtextOptions, (wordBreak | scrollVertical));	i++;
     newSource = XtStringSourceCreate(widget, args, i);
     XtTextSetSource(widget, newSource, 0);
     XtStringSourceDestroy(oldSource);

Note that I don't know whether the setting of the textOptions is useless
or not. The documentation is quite vague on the question of which resources
are destined for the source, and for the sink. Anyway, the long and short
of this is that it doesn't work. The starting position in the text widget
is set correctly, but the length doesn't seem to have any effect. In
fact, everything from the new starting position (represented by a pointer
into the buffer) to the END OF THE BUFFER is displayed! This is a real
mystery, since I have no idea how the text widget knows how large the
entire buffer is. I suspect that it runs into a large contiguous
section of nulls or something and gives up. It also may be that the
old Source length is maintained somehow (which usually is the length
of the entire buffer the first time around). In order to get this to work
properly, I had to do the following after creating the new source:

	...
     XtTextDisableRedisplay(widget);
     XtTextSetSource(widget, newSource, 0);
     XtStringSourceDestroy(oldSource);
     XtTextSetLastPos(widget, .. new length ..);
     XtTextEnableRedisplay(widget);


Any clues?

				Jordan
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