They are related with the Chinese or Japanese input method on macOS. The bug appeared after this commit:
http://git.savannah.gnu.org/cgit/emacs.git/commit/?h=emacs-25.1&id=9e77c1b7bcfd0807be7fe67daf73c2320e864309.
The workaround is setting `redisplay-dont-pause’ to nil. But this variable is obsolete since 24.5.
I think the cause may be like this:
On every char inputting, the input method triggers two events to emacs. The first event causes emacs to redisplay the window with cursor at the original position.
The second event causes emacs to redisplay the window with cursor at the new position. The two redisplay make the cursor flicker. The problem is the first redisplay which is not wanted.
If
`redisplay-dont-pause’ is t, the first redisplay may be cancelled or merged with the second one?
How to debug this problem? I want to first print the value of the variable `c’ in read_char() in keybord.c. Its type is Lisp_Object. How to print its value?