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From: cjmchale@cs.tcd.ie (Ciaran McHale)
Newsgroups: comp.windows.x.motif
Subject: Re: Infinitely-scrollable list widget?
Message-ID: <1991Feb20.184938.28788@cs.tcd.ie>
Date: 20 Feb 91 18:49:38 GMT
References: <1991Feb20.022721.8463@intek01.uucp>
Organization: DSG, Dept. of Comp. Sci., Trinity College, Dublin.
Lines: 44

In <1991Feb20.022721.8463@intek01.uucp>
mark@intek01.uucp (Mark McWiggins) writes:

>I'm building a Motif interface to our in-house database system.  Part of
>the interface is a browser for the database tables.  I'm currently using
>a List widget with a ScrolledWindow parent.
>
>This works OK if I'm willing to set the list up completely in advance, but
>it presents problems for scrolling over, say, a database table of  1 million
>rows.

The maximum size of a X window is 2**16 -1 pixels high/wide.
So it is impossible to have a container widget/window which
holds ~1 million other windows/widgets. Windows just can't
be that large. You can, of course, code around this but
beware that many container widgets won't be able to cope.
Also, if you plan on having a separate window/widgets for
each row then that's 1 million windows/widgets! The X server
may well run out of memory (if your client doesn't first).

>Ideally I need something that would let me keep a small list, with
>a callback procedure to keep refreshing the list "in the background" as
>the user uses the mouse to scroll. The ScrollBar widgets contain appropriate
>callbacks, but the user can also scroll by dragging down the list itself.
>The List widget only contains callbacks that occur after the selection is 
>made, and that's not soon enough.
>
>Can anybody point me toward a widget that's designed for this sort of thing,
>or some obvious way of doing it with the standard widget set?  I have
>Motif 1.0 (with X11R3, of course) on an Apollo. 

I don't know of any widget that does exactly what you want.
(But then I don't use Motif; maybe it has a suitable one.)
If you can't find a suitable widget then you could always
write your own. (There are several books available,
including Doug Young's one, which discuss widget writing.)


Ciaran.
-- 
Ciaran McHale		"Verbosity says it all"			      ____
Department of Computer Science, Trinity College, Dublin 2, Ireland.   \  /
Telephone: +353-1-772941 ext 1538	FAX: +353-1-772204	       \/
Telex: 93782 TCD EI			email: cjmchale@cs.tcd.ie