GNU bug report logs - #19576
24.4; Broken function in `window-size-change-functions' cause `write-file' to write the wrong buffer

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From: Eli Zaretskii <eliz <at> gnu.org>
To: acm <at> muc.de
Cc: 19576 <at> debbugs.gnu.org, andlind <at> gmail.com, juri <at> linkov.net
Subject: bug#19576: write-file writes the wrong buffer
Date: Sat, 21 Nov 2015 13:35:02 +0200

> Date: Thu, 19 Nov 2015 18:03:39 +0200
> From: Eli Zaretskii <eliz <at> gnu.org>
> Cc: 19576 <at> debbugs.gnu.org, andlind <at> gmail.com, juri <at> linkov.net
> 
> > Date: Wed, 18 Nov 2015 23:23:04 +0000
> > Cc: martin rudalics <rudalics <at> gmx.at>, juri <at> linkov.net, andlind <at> gmail.com,
> >   19576 <at> debbugs.gnu.org
> > From: Alan Mackenzie <acm <at> muc.de>
> > 
> > > Could you try a simpler patch below?  It seems to fix both your test
> > > case and the one originally reported in bug#21333.
> > 
> > It does indeed fix my test case (I haven't tried it on #21333).  However
> > it violates the specification of window-size-change-functions, which
> > says that the hook is called _before_ redisplay, not after it has
> > started.  I suppose one could argue over what "redisplay" means here,
> > but intuitively I would say it is the putting of glyphs into matrices.
> 
> "Redisplay" is indeed not defined well enough, but the only reasonable
> interpretation of "before redisplay" is that it happens before the
> call to redisplay_internal.  And this is false for your suggested
> solution as well.  It is false even by your definition, because
> prepare_menu_bars already manipulates the glyph matrices, the ones it
> creates for the tool bar (and also menu bar on some display types).
> And display_echo_area also manipulates glyph matrices (it calls
> try_window).
> 
> Which is only logical for an event that by itself is triggered as part
> of redisplay!  It's redisplay that decides to resize the mini-window,
> so calling the hook after that decision _cannot_ possibly count as
> being "before redisplay".
> 
> IOW, once we, by popular demand, decided to call
> window-size-change-functions when the mini-window is resized, we
> invalidated that specification.  All the other callers of this hook
> are not part of a redisplay cycle, but this one is, and cannot be
> anywhere else.
> 
> So no matter what change we eventually install, the documentation of
> the hook needs to be amended to say that it's called "before redisplay
> or at the beginning of a redisplay cycle", and maybe also mention that
> the second case is when the mini-window is resized.

No further comments, so I've committed the changes I posted here
earlier.  I also modified the documentation to be consistent with what
the code does.

Please tell me if this bug and bug#21333 could now be closed, or if
there are any leftovers.

Thanks.

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