[mcclim-devel] Re: [mcclim-cvs] CVS mcclim (scroll-extent vs. move-sheet)

[Andy Hefner]

On 10/28/06, thenriksen <thenriksen at common-lisp.net> wrote:
> +      ;; XXX: We cannot use `scroll-extent', because McCLIM ignores it
> +      ;; unless the scrollee happens to be drawing. Very weird, should
> +      ;; be fixed.

I think I finally deciphered the purpose of the method in
recording.lisp which defines this odd behavior: to supress scrolling
of the stream when recording output to an offscreen record (such as
using with-output-to-output-record). This is a legitimate concern, and
simply removing the method would be wrong. This suggests that output
to an offscreen output record should also not cause the stream-pane to
be resized. McCLIM does not guard against this case. The following
program demonstrates the problem:

(in-package :clim-user)

(define-application-frame oops-1 ()
  ()
  (:pane
   (scrolling (:width 300 :height 300)
     (make-pane :application-pane
		:end-of-line-action :allow
                :end-of-page-action :allow
		:display-function
		(lambda (frame stream)
                  (with-output-to-output-record (stream)
                    (dotimes (i 200)
                      (format stream "~&You never see this.~%")))
                  (format stream "All those scrollbars for this little
line of text?~%"))))))

The correct solution might involve checking that the open output
record is connected to the stream output history, and supressing
resizing and scrolling only if it is not (indicating offscreen
drawing). Hmm.