GNU bug report logs - #21869
Redisplay: after echo area diminishes in size, Follow Mode windows aren't resynchronised.

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From: Eli Zaretskii <eliz <at> gnu.org>
To: 21333-done <at> debbugs.gnu.org, 21869-done <at> debbugs.gnu.org
Subject: bug#21869: bug#19576: write-file writes the wrong buffer
Date: Sat, 21 Nov 2015 18:02:39 +0200

> Date: Sat, 21 Nov 2015 15:56:58 +0000
> Cc: 19576 <at> debbugs.gnu.org, andlind <at> gmail.com, juri <at> linkov.net
> From: Alan Mackenzie <acm <at> muc.de>
> 
> Hello, Eli.
> 
> On Sat, Nov 21, 2015 at 01:35:02PM +0200, Eli Zaretskii wrote:
> > > 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.
> 
> Thanks.
> 
> > Please tell me if this bug and bug#21333 could now be closed, or if
> > there are any leftovers.
> 
> I don't think this fix concerns #19576.  The discussion of #21869 seems,
> somehow, to have moved to here.
> 
> But I think that #21333 can be closed, and #21869 certainly can be; both
> of these were about window-size-change-functions not getting called for
> echo area size changes.

Closing.

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