bug#23026: 25.0.92; menu-bar bug?

[Leo Liu]

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.

Make sense and thanks for the info.

>> 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.

Thanks.

Leo