Fix posframe usage for lsp-ui-doc

[brotzeit]

it causes the hover window to capture focus, making editing impossible.

The posframe integration on lsp-ui is slow, due to new frame is being created every time.

[Sorixelle]

In my testing, I didn't run into either of these issues while working on #459. If anyone is experiencing these issues, I'd like to get some more details on the environment this is occuring in so I can try and reproduce these.

[dmakarov]

This happens to me on macOS 10.15.5: GNU Emacs 26.3 (build 1, x86_64-apple-darwin18.2.0, NS appkit-1671.20 Version 10.14.3 (Build 18D109)) of 2019-09-02. I don't have any customizations for lsp-ui or posframe group.

Here I move pointer to a method name, lsp-ui-doc pops up and it has focus. I press q to switch focus back to the original frame.

[yyoncho]

@alanz are you also using macos?

[Sorixelle]

Did some testing, and managed to get to the bottom of the focus issues. It seems to be an issue with Cocoa builds of Emacs. This issue doesn't exist in the emacs-mac port, so the solution would be to use this. It seems like this is an Emacs bug, and completely out of our control. More info in this issue in posframe.

[yyoncho]

It seems like this is an Emacs bug, and completely out of our control

It was working in the previous implementation, right?

[Sorixelle]

Just reverted the commit, it seems like it did work on Cocoa builds. I'm still unconvinced this is a problem on our side however, as I don't see any reason our code would cause the new frame to get focus.

[dmakarov]

This may be a macOS cocoa issue, but the previous non-posframe implementation did work.

[Sorixelle]

I've come up with a solution that works for Emacs 26 on macOS. However, this solution prevents using the mouse to focus the frame in Linux, and doesn't fix the issue in Emacs 27 or 28 on macOS (no clue why). Also of note is that in Emacs 28 in macOS, it seems to completely ignore positioning and just display in the top-left corner of the screen. If we're ok with losing the ability to focus with the mouse outside of macOS, I'll make a PR with this fix.

The solution is to not advise posframe--redirect-frame-focus, and just let it setup the focus redirect. lsp-ui-doc-focus-frame still works, but the mouse can still focus the frame in Emacs 26 for some reason.

tl;dr - Emacs on macOS is really, really weird.

EDIT: The Emacs 27/28 issues might have something to do with the obsoletion of focus-in-hook for after-focus-change-function. That should probably be reported to posframe.

[yyoncho]

IMO not getting the focus is better than getting the focus all the time. Ideally, we should not introduce regression compared to the previous behaviour of the popup.

[alanz]

@alanz are you also using macos?

Yes, the problem shows up on my work machine, macos. But not on my home machine, Debian Testing.

[kiennq]

@Sorixelle
About this

The posframe integration on lsp-ui is slow, due to new frame is being created every time.

A simple profiling will reveal that

- #<compiled 0x347b065>                                                                         266  88%
 - lsp--parser-on-message                                                                       266  88%
  - #<compiled 0x4297c65>                                                                       266  88%
   - #<compiled 0x4297c49>                                                                      266  88%
    - #<compiled 0x4297c15>                                                                     266  88%
     - apply                                                                                    266  88%
      - #<compiled 0x4294071>                                                                   266  88%
       - lsp-ui-doc--callback                                                                   266  88%
        - lsp-ui-doc--display                                                                   266  88%
         - lsp-ui-doc--make-frame                                                               265  88%
          - posframe-show                                                                       260  86%
           - posframe--create-posframe                                                          255  85%
            - make-frame                                                                        255  85%
             - frame-creation-function                                                          255  85%
              - apply                                                                           255  85%
               - #<compiled 0x1072a75>                                                          255  85%
                + x-create-frame-with-faces                                                     255  85%
             posframe--set-frame-position                                                         2   0%
             posframe--mouse-banish                                                               1   0%
          + lsp-ui-doc--delete-frame                                                              5   1%
+ redisplay_internal (C function)                                                                25   8%
+ timer-event-handler                                                                             5   1%
+ ...                                                                                             2   0%
+ eldoc-pre-command-refresh-echo-area                                                             1   0%

It calls make-frame on every lsp-ui-doc--display request, which is slow on some system.
Even the default implementation of posframe try to avoid that by associating an posframe--frame with every posframe buffer so it will not be created again.

In case of lsp-ui, why this happens is because of this check inside lsp-ui-doc--display.

      (when (or (not lsp-ui-doc-use-webkit)
                (not (lsp-ui-doc--get-frame)))
        (lsp-ui-doc--set-frame (lsp-ui-doc--make-frame)))

So just simply not set lsp-ui-doc-use-webkit will make this check passed and calling lsp-ui-doc--make-frame.
Inside lsp-ui-doc--make-frame, it intentionally delete the posframe with lsp-ui-doc--delete-frame and causes new frame to be created everytime.
I believe this check is mistyping and should change from or to and, or simply change to use unless and remove not instead of when.

However, just changing that will not work since the posframe position will not be updated. In the original code, the frame position is updated in every call to lsp-ui-doc--display with lsp-ui-doc--move-frame, we need to update that with posframe too (call posframe-show with new position, I guess).

Alternatively, change the check to check for lsp-ui-doc-use-webkit only and remove the delete frame from lsp-ui-doc--make-frame may work too. We will still calling stuff of setting up frame parameters every time though.

[omidmnz]

I have this problem on NixOS, so the issue is definitely not OSX-specific. But I'm using xmonad, so it might be a contributing factor.

[seagle0128]

Same issue here after I upgraded today. It's pleasure to provide details if need.