Arabic characters are misaligned when notermbidi #14115

Steps to reproduce

1. Paste this text

السَّلامُ عليْكُم

2. :set arabic

Expected behaviour

Two problems:

• Diacritics are mispositioned.
• Positioning cursor on a letter, then inserting or appending puts the cursor ahead of the wrong letter.

Version of Vim

9.1

Environment

Terminal: Alacritty.

But I think it would work for any terminal with no Arabic shaping support. As I explained here (#9761 (comment)), Vim :set arabic seems to expect that the terminal won't do any shaping, and so by far, it's the only way (I know of) to correctly display Arabic in Vim.

Font: DejaVu Sans Mono and Noto Sans Mono.

Logs and stack traces

No response