Re: Need help to debug bugs(#22989, #23412)

[Eli Zaretskii <eliz@gnu.org>]

> From: HaiJun Zhang <netjune@outlook.com>
> Date: Sun, 27 Oct 2019 03:10:56 +0000
> 
> 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 But this variable is obsolete since 24.5.

If your analysis is correct, then maybe input methods (or their users,
if you mean a non-Emacs input method) should set redisplay-dont-pause
nil, and we should un-obsolete that variable.

But the question is: do both events you mention arrive with any time
interval between them, or do they arrive together?  IOW, the issue is
about timing, not about the number of events.

> 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?

You mean, print in C?  You can use the safe_debug_print function.