[vim/vim] PopupBorder is clipped. (Issue #21128)

mao-yining created an issue (vim/vim#21128)

### Steps to reproduce

<img width="1570" height="983" alt="Image" src="https://github.com/user-attachments/assets/fe0c98bc-2968-4251-bccb-c9054143d72e" />

<img width="2164" height="1163" alt="Image" src="https://github.com/user-attachments/assets/db0bf37f-a6e0-478e-a6e4-10c51f2ce433" />

### Expected behaviour

Border is shown completely.

### Version of Vim

9.2.976

### Environment

WSL Ubuntu.
MS-Windows
Windows Terminal.

### Logs and stack traces

```shell

```

-- 
Reply to this email directly or view it on GitHub:
https://github.com/vim/vim/issues/21128
You are receiving this because you are subscribed to this thread.

Message ID: <vim/vim/issues/[email protected]>

-- 
-- 
You received this message from the "vim_dev" maillist.
Do not top-post! Type your reply below the text you are replying to.
For more information, visit http://www.vim.org/maillist.php

--- 
You received this message because you are subscribed to the Google Groups "vim_dev" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
To view this discussion visit https://groups.google.com/d/msgid/vim_dev/vim/vim/issues/21128%40github.com.