From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 32874@debbugs.gnu.org
Subject: bug#32874: Unwanted scrolling in edebug `f' command when follow-mode is active
Date: Sat, 29 Sep 2018 15:37:29 +0000 [thread overview]
Message-ID: <20180929153729.GD5008@ACM> (raw)
In-Reply-To: <83lg7k5q2o.fsf@gnu.org>
Hello, Eli.
On Sat, Sep 29, 2018 at 17:35:43 +0300, Eli Zaretskii wrote:
> > Date: Sat, 29 Sep 2018 14:09:57 +0000
> > From: Alan Mackenzie <acm@muc.de>
> > The immediate cause of this is at edebug--recursive-edit L+86, where
> > there is a call to (sit-for 0). If this call is commented out, and the
> > bug scenario repeated, there is no spurious scrolling. That call is
> > there for a reason, however, so this isn't a fix for the bug.
> What is the reason for calling sit-for? Can the call to sit-for be
> replaced with something else when follow-mode is in effect and we
> aren't in the last window of the follow group?
sit-for is called right after (edebug-overlay-arrow), I think, to ensure
that the newly placed arrow is actually drawn on the screen.
I can't think of any replacement for this sit-for at the moment.
> > The use of post-command-hook for follow mode is clearly suboptimal.
> > Follow mode is essentially a part of redisplay, so it ought to get called
> > from a redisplay hook. The trouble is, `redisplay-hook' doesn't exist.
> Actually, redisplay-hook is not well defined, because different
> potential customers of such a hook would like that hook to be called
> from different parts of the redisplay cycle and under different
> conditions. Thus we have pre-redisplay-function instead, and a few
> other specialized hooks the display engine calls, like
> window-scroll-functions.
OK, that sounds like a good reason for not having such a hook. :-(
> > The best available hooks which might serve seem to be
> > pre-redisplay-function or pre-redisplay-functions. Unfortunately, these
> > are called too late, after redisplay has already determined which windows
> > to operate on.
> That's not true: pre-redisplay-function is called _before_ the display
> engine determines what window(s) might need to be redrawn.
Thanks! I'll have a look at pre-redisplay-function, and see if I can do
anything with it.
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2018-09-29 15:37 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-29 14:09 bug#32874: Unwanted scrolling in edebug `f' command when follow-mode is active Alan Mackenzie
2018-09-29 14:35 ` Eli Zaretskii
2018-09-29 15:37 ` Alan Mackenzie [this message]
2018-09-29 16:09 ` Eli Zaretskii
2018-09-29 20:41 ` Alan Mackenzie
2018-09-30 7:35 ` Eli Zaretskii
2018-09-30 15:36 ` Alan Mackenzie
2018-09-30 17:17 ` Eli Zaretskii
2018-10-01 12:59 ` Alan Mackenzie
2018-10-01 13:52 ` Eli Zaretskii
2018-09-30 14:45 ` Alan Mackenzie
2018-10-03 10:54 ` Alan Mackenzie
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