Path: utzoo!utgpu!news-server.csri.toronto.edu!neat.cs.toronto.edu!tjhorton
Newsgroups: comp.windows.x.motif
From: tjhorton@cs.toronto.edu ("Timothy J. Horton")
Subject: Re: How to re-manage the same child widget
Message-ID: <91May16.230552edt.6244@neat.cs.toronto.edu>
Organization: Department of Computer Science, University of Toronto
References: <91May16.183920edt.8838@orasis.vis.toronto.edu>
Distribution: inet
Date: 17 May 91 03:06:10 GMT
Lines: 34

Let me get this right the second time

tjhorton@vis.toronto.edu ("Timothy J. Horton") writes:
>Most motif widgets are like this; they reallocate copies of whatever you give
>them via pointers.

          (using *either* XtSetValues or convenience routines)

>Furthermore, if you fetch back resource values via pointers,

          USING CONVENIENCE ROUTINES SUCH AS "XmTextGetString",
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

>most widgets allocate yet another copy of the resource and pass back the new
>copy, which you normally have to free explicitly.

XtGetValues normally bypasses this copy/free cycle.  For instance,
XmTextGetString gives you a *copy* of the text widget's internal buffer,
wheras XtGetValues on its XmNvalue returns a pointer to the text widget's
internal buffer.

Thus, getting and setting are different.

>I had an application in which I needed to very quickly swap large lists in
>and out of a list widget, but couldn't, because the dang list widget always
>freed its old list and allocated and copied the new one.  I had to write my
>own code from scratch to display selection lists without copying them.

Someone asked about this -- I just used a drawing area and a scrollbar, and the
input callback from the drawing area for item selection.  I don't have the code
(now belongs to a previous client), but it only took a day to write, except
that it required some messy Xlib hacking.

Tim