exwm-input--update-focus cause key not sent to input-method-function

[QiangF]

See the debug log here,
https://gist.github.com/QiangF/3da9f935354d31657a056ef31c6127cf

Every time exwm-input--update-focus is run, one key (118) is not processed by the input method, the focused window does not changing,, the focus actually does not need update. Is the input method disabled during that instant?

[QiangF]

I think the fix will be: if the focus did not change, don't run that function.

[QiangF]

Seems to be fixed by #706

[ch11ng]

That change may have some unintended side effects I'm afraid. I wonder why there was a change in buffer-list. I didn't find the definition of rime-input-method though.

[QiangF]

rime-input-method is my simplified chinese input method:
https://gist.github.com/QiangF/d726722d4ceee0cd31fc59163ae2a5bd
I put exwm--log there to print the key received by input method. I have not seen any side effect by far.

There might be better fix if we know the reason for the issue.

[QiangF]

The change in buffer-list is probably because I use a temporary buffer for the preedit. Also exwm-xim has a " *temp*" buffer.

[ch11ng]

I've not tried it myself but it seems your input method does call functions like get-buffer-create which in turn run buffer-list-update-hook.

[ch11ng]

What about let-bind exwm-input--skip-buffer-list-update to t so as to skip certain calls to buffer-list-update-hook? This should not be abused though.

[QiangF]

No, "let-bind exwm-input--skip-buffer-list-update to t" doesn't work.
I tried set it both in exwm-xim:

         (let ((input-method-use-echo-area t)
               (exwm-input--skip-buffer-list-update t))
               (with-temp-buffer

and in my input method:

(defmacro rime-with-preedit (&rest forms)
(declare (indent 0) (debug t))
`(let ((exwm-input--skip-buffer-list-update t))
    (with-current-buffer
        (get-buffer-create " *rime-preedit*")
    ,@forms)))

I have type 7 key 118, and the last one is lost, see the debug output:

https://gist.github.com/QiangF/721dec58a86405dc72fdde3dfade2c61

[QiangF]

There are many other command that create invisible buffers, to find out each of them is impossible. If both the focused buffer and the current window doesn't change, does that mean the focus has not changed? why do you need to update the focus in this case?

[ch11ng]

If both the focused buffer and the current window doesn't change, does that mean the focus has not changed?

No. All X clients can change input focus, or we won't have to take the trouble to set it every possible time.

[QiangF]

I think there are 3 possible solutions:

1. during exwm-input--update-focus, don't process key event, like (push key unread-command-events)
2. don't run exwm-input--update-focus when the buffer update is due to normal emacs buffers (non exwm mode buffers), especially hidden buffers
3. use the pull request solution: I have not find any issues so far with that.

[ch11ng]

Solution 2 is the most nature way to go if feasible. There was a implementation which can be broken sometimes. You can stick to that PR until we work out another implementation.