exwm-layout--refresh-workspace is slow with many windows

[Stebalien]

Whenever I open a minibuffer or re-arrange a window, EXWM runs exwm-layout--refresh-workspace. Unfortunately, I often have many (~75) windows open (I use windows with Firefox instead of tabs so I can manage them with EXWM).

This means 10-15% of the time is spent iterating over all the open windows.

With native-comp enabled:

- redisplay_internal (C function)                                 161  18%
 - exwm-layout--refresh                                           133  15%
  - exwm-layout--refresh-workspace                                 88  10%
   - exwm-layout--show                                             32   3%
    + exwm--set-geometry                                            4   0%
    + window-inside-absolute-pixel-edges                            3   0%
    + exwm-layout--set-ewmh-state                                   1   0%
    + xcb:flush                                                     1   0%
   + xcb:flush                                                      2   0%
   + exwm-layout--set-client-list-stacking                          1   0%

Without:

- redisplay_internal (C function)                                 124  13%
 - exwm-layout--refresh                                            97  10%
  - if                                                             97  10%
   - exwm-layout--refresh-workspace                                97  10%
    - let                                                          96  10%
     - dolist                                                      41   4%
      + cl-block                                                   41   4%
     - exwm-layout--set-client-list-stacking                        9   1%
      + xcb:-+request                                               9   1%
     + xcb:flush                                                    3   0%
     + let                                                          1   0%

[Stebalien]

(note: this is hardly a high priority, just something I've noticed)

[ch11ng]

Do you have exwm-layout-show-all-buffers turned on or are all the X windows on a same workspace?

exwm-layout--refresh-workspace is suboptimal in that it performs exwm-layout--show or exwm-layout--hide on all X windows on a certain workspace. This can be avoided if we trust the state of each X window.

[Stebalien]

Do you have exwm-layout-show-all-buffers turned on or are all the X windows on a same workspace?

Both. I try to treat X windows as emacs buffers as much as possible.

This can be avoided if we trust the state of each X window.

Can X windows make themselves visible or is this just a matter of tracking known visible/invisible windows per workspace?

[medranocalvo]

(@Stebalien, could you have a look at #688/#737?)

I don't think it's easy. exwm-layout--refresh gets called in various circunstances (visible buffers changed [which could mean the X window must be moved to other workspace], window sizes changed, minibuffer, etc.). Perhaps we can cache part of the information and only update what changed. That might be possible for the two actions you mentioned.

[ch11ng]

@Stebalien

Can X windows make themselves visible or is this just a matter of tracking known visible/invisible windows per workspace?

We'll need to save & update their states as what @medranocalvo had explained. I'd like to give this a try when I find the time.