bug#77994: 30.1; Yanking paths or Kanji from Windows produces incorrect behaviour for pgtk build on WSL2

[Eli Zaretskii]

> From: Tim Jim <redemptiontea@gmail.com>
> Date: Wed, 23 Apr 2025 01:12:15 +0900
> 
> I've compiled Emacs 30.1 on AlmaLinux 9 running in WSL2 with pgtk; as per the 
> subject, I'm seeing two
> separate bugs(?), I think. 
> 
> I ran a quick comparison using `emacs -Q`, for Emacs compiled with and 
> without `--with-pgtk`.
> 
> 1. When pasting a path copied from the address bar from Windows Explorer into 
> an Emacs buffer, the path
> is usually followed by a bunch of null characters, such as ^@ and ^A. Based 
> on my searching, this could be
> an encoding issue, but I could not find an encoding setting which solves 
> this. 
> 
> 2. Pasting in any Kanji will result in ???? appearing instead of the 
> characters. I can confirm that if I type in
> Japanese directly into the buffer, it shows up fine. Just to check it wasn't 
> a GTK on WSL problem, I also fired
> up a gedit session and could successfully paste in the Kanji there.
> 
> Both problems went away when I compiled without `--with-pgtk`. I.e. I could 
> paste in paths without extra null
> characters appearing and could paste in Kanji successfully.
> 
> I'm unsure if this is a bug, or if it's a difference in how system 
> environmental variables are handled. Please
> could you give me some pointers on how/if this can be resolved? 
> 
> Thanks for all your efforts supporting and developing Emacs!
> 
> P.S. as a quick addendum to point 1, I had also posted an earlier variation 
> of the question that also included
> an issue that did turn out to be an encoding issue (trying to paste a degree 
> symbol). That part was solved
> using `(setq selection-coding-system nil)`, but the path issue remained, so I 
> suspected it might be a different
> problem. https://www.reddit.com/r/emacs/s/6w1L3CiyAU
> 
> If there is anything else I can add to help debug this please let me know. 
> Also, apologies if this is something
> obvious that I've missed in the manual. I tried searching the bug tracker too 
> for anything WSL-specific, but I
> didn't see anything immediately relevant. 

Thanks.

We don't have experts on board who know how WSL2 works wrt
interoperability between Windows and Ubuntu, so what GTK does in that
case is a mystery to us, I think.  I've added Po Lu to the discussion
in the hope that he might have some suggestions.

I personally have only one idea: try

  C-x RET x utf-16-le RET

and see if this fixes the problems you see.

I suspect that WSL2 has some customization options which control how
the Windows clipboard is presented to GNU/Linux programs running in
Ubuntu.

Or maybe you need something to be installed, like xclip or
wl-clipboard.