Non-Emacs windows blink when Mingus window is open

[kahrkunne]

Opening a window with Mingus (https://github.com/pft/mingus) somewhere makes X windows (i.e. Chrome etc) blink with my Emacs background colour when in focus.

EDIT: only happens in the mingus playlist, not in the browser or controls page

[ch11ng]

The problem is mingus sets up an idle timer that would call force-mode-line-update to update the mode-line when Emacs gets idle, and that it also sets up the mode-line so that Emacs would call mingus-make-mode-line-string when updating the mode-line. mingus-make-mode-line-string interacts with mpd through libmpdee that involves some process handling stuffs conflicting with XELB or EXWM.

[kahrkunne]

I see. That must be related to mingus' ability to display the currently playing song.

For what it's worth, I've tried running (defun mingus-make-mode-line-string (lambda () nil)) because I don't actually need that behaviour, but that doesn't fix the problem; the windows no longer blink the background colour, but they still blink in and out of focus.

[ch11ng]

Sorry for leaving out one thing. mingus-make-mode-line-help-echo also gets called during that time. Please try redefining mingus-mode-line-object to something like "".

[kahrkunne]

Doesn't solve the problem, sadly.

[ch11ng]

(setq mingus-mode-line-object "") seems to fix the problem here. You need to set this variable before calling mingus.

[kahrkunne]

It does not fix the problem here. The chrome window doesn't blink the background colour anymore, but it still blinks, and typing is essentially impossible.

[ch11ng]

Is #264 related?

[tidux]

I'm pretty sure this is just Mingus calling (redisplay) and not technically a bug in exwm or Emacs.

[ch11ng]

@tidux Could you elaborate on this?

[tidux]

Mingus uses (redisplay) to redraw itself once a second. For normal emacs windows this isn't an issue, but for X windows it causes blinking at that same pace since they get forcibly redrawn from scratch. My fix was using other mpd clients, like ncmpcpp in urxvt, or Cantata.

[ch11ng]

@tidux Thanks but did you mean Mingus indirectly called redisplay? I didn't find any direct call in its source (https://github.com/pft/mingus)?

[kahrkunne]

(run-with-idle-timer 1 t #'redisplay), which runs (redisplay) once a second, was not able to reproduce the issue, so that can't be it.

[kahrkunne]

Running mingus-cancel-timer with mingus open seems to at least temporarily fix the problem. I'll look through the source code and see how I can reproduce the issue.

EDIT: the offending line is (mingus-set-NP-mark t)

EDIT2: I've narrowed the offending code down to

(save-excursion
  (save-window-excursion
    (mingus-switch-to-playlist)))

The problem seems to be that mingus is constantly switching buffers to its playlist and back; that's the flickering we're seeing. The window that our currently focused buffer (in our case, an X buffer) is in switches to the Mingus buffers for a split second.
The relevant code is this:

(defun mingus-switch-to-playlist ()
  (cond
   ((get-buffer-window "*Mingus*")
    (select-window (get-buffer-window "*Mingus*")))
   (t
    (switch-to-buffer "*Mingus*")))
  (mingus-playlist-mode))```

[kahrkunne]

I think I'm gonna call this a Mingus bug... Thinking about it, Mingus is basically relying on being able to switch buffer sufficiently quick that it never renders.

EXWM isn't the only package which has problems with this; ace-window also has a bug when using in combination with mingus.

EDIT: I've submitted an issue to the EXWM bug tracker (pft/mingus#26). However, that bug tracker hasn't been active since january 2015, so I'm unsure if mingus is even supported anymore...

[ch11ng]

@kahrkunne Thanks for your work!

[ch11ng]

@kahrkunne I'd assume there is nothing can be done here. So I'm closing this issue now.