Re: describe-{function,variable} shrinks frame (GTK+/KDE)

[Stephen Berman]

On Sat, 17 Nov 2007 10:16:17 +0100 martin rudalics <address@hidden> wrote:

>> This recipe isn't completely reliable: what seems to be constant are the
>> prior invocation of Info and unsplitting the windows between the
>> describe-* calls; otherwise, sometimes the shrinkage happens after the
>> first call to describe-{function,variable}, sometimes it takes several
>> iterations of steps 2.-5.  The function/variable names are examples,
>> probably any will do.  Once the shrinkage begins, it progresses with
>> subsequent describe-* calls.
>
> Leaving an Emacs frame for some time unattended with
>
> (defun foo ()
>   (interactive)
>   (while t
>     (split-window)
>     (when (zerop (logand (random) 1))
>       (other-window 1))
>     (sit-for 0.5)
>     (if (zerop (logand (random) 1))
>       (delete-window)
>       (delete-other-windows))
>     (sit-for 0.5)))
>
> doesn't show the behavior (just to rule out more trivial causes like
> window splitting / deleting)?

No, this does not change frame-height.  In fact, I had already manually
tried repeatedly splitting and unspitting and did not see any problem.
But your test gave me an idea to try and reproduce the behavior I
observed programmatically.  I started Emacs with -Q and evalled the
following functions:

(defun srb-randsym ()
  "Return a random Emacs lisp symbol."
  (random t)
  (let* ((rnum (random (length obarray)))
         (elt (aref obarray rnum)))
    elt))

(defun srb-shrink-test-0 ()
  "Call Info, then repeatedly call describe-function or
describe-variable on a random elisp function or variable, deleting
the Help buffer in between.  If the frame height changes, stop."
  (interactive)
  (info)
  (let ((ht (frame-height))
        elt)
    (message "frame height: %d" ht)
    (sit-for 0.5)
    (setq elt (srb-randsym))
    (while (not (or (functionp elt) (boundp elt)))
      (setq elt (srb-randsym)))
    (cond ((functionp elt) 
           (describe-function elt))
          ((boundp elt) 
           (describe-variable elt))
          (t 'ignore))
    (sit-for 0.5)
    (delete-other-windows)
    (sit-for 0.5)
    (if (= ht (frame-height))
        (srb-shrink-test-0)
      (message "frame height: %d" (frame-height)))))

I invoked srb-shrink-test-0 and let it run though many iterations, but
frame-height remained unchanged.  Then I evalled the following function,
which differs from the above only in calling
describe-{function,variable} interactively:

(defun srb-shrink-test-1 ()
  "Call Info, then repeatedly call describe-function or
describe-variable interactively, deleting the Help buffer in
between.  If the frame height changes, stop."
  (interactive)
  (info)
  (let ((ht (frame-height))
        elt)
    (message "frame height: %d" ht)
    (sit-for 0.5)
    (setq elt (srb-randsym))
    (while (not (or (functionp elt) (boundp elt)))
      (setq elt (srb-randsym)))
    (cond ((functionp elt) 
           (call-interactively 'describe-function))
          ((boundp elt) 
           (call-interactively 'describe-variable))
          (t 'ignore))
    (sit-for 0.5)
    (delete-other-windows)
    (sit-for 0.5)
    (if (= ht (frame-height))
        (srb-shrink-test-1)
      (message "frame height: %d" (frame-height)))))

I invoked this and frame-height diminished by one line after the first
interactive call.  I have repeated this many times and every time
frame-height has shrunk, whereas with srb-shrink-test-0 it has never
shrunk.  It seems that call-interactively is somehow involved in
shrinking frame-height.  I looked at the source code but found nothing
suggestive; but it is a very long and complex function, and I don't know
what to look for.  It doesn't help that this problem seems to be
restricted to GTK+ builds running under gtk-qt.

Steve Berman