scrolling to the bottom of a window

I have a fair number of little `stream viewer' thingies.  These are
just wrappers around CAPI COLLECTOR-PANEs to which I send various
random typeout.

Is there an easy way to cause one of these things to scroll to the
bottom on output?  What I want is something that will try and make
sure that the most recent output to the stream is visible in the
window.  I'm sure this is easy but I can't see how to do it.

Thanks

--tim

(BTW if anyone ever used it, I recently put a newer version of my CLC
thing at www.tfeb.org.  This now uses one of these viewer windows,
which has the output-can-be-invisible problem I'm trying to solve!)

Re: scrolling to the bottom of a window

Tim Bradshaw <tfb@cley.com> writes:

> I have a fair number of little `stream viewer' thingies.  These are
> just wrappers around CAPI COLLECTOR-PANEs to which I send various
> random typeout.
> 
> Is there an easy way to cause one of these things to scroll to the
> bottom on output?  What I want is something that will try and make
> sure that the most recent output to the stream is visible in the
> window.  I'm sure this is easy but I can't see how to do it.

Dave and I had a fairly involved discussion about that some time
ago. This is a method that works for a similar problem (making sure
the viewers are at the beginning) for LW/Linux 4.1. A new scrolling
API was announced for 4.2. If you update more than one, you need to
call redisplay yourself. Otherwise only the last one done is shown.


(defmethod fill-collectors ((interface test-case-4))
  (let* ((collector-1-stream (capi:collector-pane-stream (collector-1 interface)))
         (collector-2-stream (capi:collector-pane-stream (collector-2 interface))))
    (loop repeat 100
          do
          (format collector-1-stream "1: Hello world!~%")
          (format collector-2-stream "2: Hello world!~%"))
    (capi:execute-with-interface interface
                                 #'(lambda (pane)
                                     (capi:call-editor pane "Beginning of Buffer")
                                     (editor:redisplay))
                                 (collector-1 interface))
    (capi:execute-with-interface interface #'capi:call-editor (collector-2 interface) "Beginning of Buffer")
    ))

-- 
Bored, now.
Lieven Marchand <mal@wyrd.be>

Re: scrolling to the bottom of a window

----- Original Message -----
From: "Tim Bradshaw" <tfb@cley.com>
To: <lisp-hug@xanalys.com>
Sent: Thursday, August 22, 2002 10:50 AM
Subject: scrolling to the bottom of a window


> I have a fair number of little `stream viewer' thingies.  These are
> just wrappers around CAPI COLLECTOR-PANEs to which I send various
> random typeout.
>
> Is there an easy way to cause one of these things to scroll to the
> bottom on output?  What I want is something that will try and make
> sure that the most recent output to the stream is visible in the
> window.  I'm sure this is easy but I can't see how to do it.
>
> Thanks
>
> --tim
>
> (BTW if anyone ever used it, I recently put a newer version of my CLC
> thing at www.tfeb.org.  This now uses one of these viewer windows,
> which has the output-can-be-invisible problem I'm trying to solve!)
>
>
>
An alternative to Lieven Marchand's method which may be simpler: (LWW 4.2.6)

(setq pane (capi:contain (make-instance 'capi:collector-pane)))

then put some text in the pane, either by typing or otherwise.

Then
(capi:scroll pane :vertical :page 10) moves 10 pages down
(capi:scroll pane :vertical :page -10) moves 10 pages up

If there are aren't 10 pages, seems not to matter so:
(capi:scroll :vertical :page most-positive-fixnum)
is fairly likely to get you to the bottom of the pane ;-)

The capi reference manual says to use the scroll generic function, as
set-scroll-position is deprecated.

Jim Bushnell