bug#23412: 25.1.50; GUI Emacs on Mac OS X: text is keeping shaking/re-displaying when insert text with external input method

[Chunyang Xu]

For example, when I try to insert "中文" with "zhongwen" via the
built-in Pinyin input method, "zhongwen" is keep shaking, here is a
video of this very annoying behavior:

https://youtu.be/56oLXo2wwJQ

It looks like only Emacs has this problem, other apps like TextEdit works fine.

I have following font setting in my init.el and don't set any Chinese
font manually.

;; Font#
(set-face-attribute 'default nil
                    :font "Source Code Pro-13")

Let me know if I need to provide more information.

In GNU Emacs 25.1.50.1 (x86_64-apple-darwin15.4.0, NS appkit-1404.46 Version 
10.11.4 (Build 15E65))
 of 2016-04-25 built on MBA.local
Repository revision: 12846626bfae795a173fdedf2850dfbd24065534
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
 'configure --with-modules'

Configured features:
JPEG RSVG IMAGEMAGICK NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS
NS MODULES

Important settings:
  value of $LANG: en_CN.UTF-8
  locale-coding-system: utf-8-unix