[debbugs-tracker] bug#23026: closed (25.0.92; menu-bar bug?)

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Your message dated Thu, 17 Mar 2016 11:26:12 +0800
with message-id <address@hidden>
and subject line Re: bug#23026: 25.0.92; menu-bar bug?
has caused the debbugs.gnu.org bug report #23026,
regarding 25.0.92; menu-bar bug?
to be marked as done.

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23026: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=23026
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--- Begin Message --- Subject: 25.0.92; menu-bar bug? Date: Wed, 16 Mar 2016 13:38:20 +0800

1. Start a GUI emacs with -q
2. load the attached t.el file
3. M-x test
4. look at the menu-bar and notice there is `Test' menu
5. mouse-click the first line and notice `Test' is gone
6. mouse-click the second line so that `Test' reappears
7. C-p to move to first line and notice `Test' doesn't disappear

The difference between 5 and 7 is puzzling. Is this a bug? How to make
the two behave consistently?

Leo

t.el
Description: t.el

--- End Message ---

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> Subject: 
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> Re: bug#23026: 25.0.92; menu-bar bug?
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> Date: 
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> Thu, 17 Mar 2016 11:26:12 +0800
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> On 2016-03-16 17:36 +0200, Eli Zaretskii wrote:
> > No, it's a redisplay optimization: Emacs doesn't redraw the menu bar
> > when all that's changed is cursor position.  In 99.999% of cases,
> > cursor motion doesn't require any changes in the menu-bar items, so
> > redrawing the menu bar after each movement of point would just slow
> > down cursor motion and cause annoying flickering of the menu bar.
> > Therefore, we don't do it.  I'm not sure I understand what's special
> > about this use case that we'd want to disable this optimization.
> >
> > By contrast, a mouse click potentially activates/deactivates the mark
> > and extends or removes the region highlight, so many redisplay
> > optimizations are disabled when we process the click -- it isn't just
> > moving point.
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> Make sense and thanks for the info.
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> >> How to make the two behave consistently?
> >
> > By "consistently" I believe you mean you'd like the menu bar updated
> > when point moves via keyboard commands, yes?  If so, you should force
> > a more thorough redisplay, e.g. by calling force-mode-line-update,
> > when point moves in a way that requires a change in the menu bar.  How
> > exactly to do that depends on your real-life use case -- it could be a
> > post-command-hook, or a special binding in the keymap which you put in
> > the property, or a function in cursor-sensor-functions property, or
> > something else.
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> Thanks.
>
> Leo
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