bug#23009: 25.0.92; xterm-mouse-mode should not assume UTF-8 coordinates

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Sat, 26 Mar 2016 22:26:17 +0000
> Cc: 23009@debbugs.gnu.org
> 
>  Hmm... what does current-input-mode return on HTerm in "emacs -Q"?
> 
> (t nil 0 7)
> 
>  I
>  expect to see a non-nil, non-t value in the 3rd element of its return
>  value. If that's so, then testing that value for identity with the
>  one we want to pass to set-input-meta-mode, and avoiding the latter
>  call if the mode is already what we want, might avoid the flickering.
> 
> Yes, that's already the case (set-input-meta-mode doesn't reinitialize the 
> terminal if the meta mode doesn't
> change), and it's why I use latin-1 instead of no-conversion. With latin-1, a 
> single mouse click results in 8
> invocations of (set-input-meta-mode 8) (two mouse events with two coordinates 
> each, and a set and reset
> per coordinate). With no-conversion, the same click results in four sequences 
> of (set-input-meta-mode t)
> (set-input-meta-mode 8), which causes the flicker.

Then I guess I'm confused about the reason for (set-input-meta-mode t)
in the case of no-conversion -- don't we want Emacs to pass the 8th
bit through without interpreting it?  Perhaps Handa-san could comment
on this, as I'm otherwise inclined to add raw-text to the list of the
coding-system types that want a non-nil, non-t value to be passed to
set-input-meta-mode.