MacVim selects one letter more to the right when selecting by mouse

[eirnym]

Steps to reproduce

1. write text
2. put cursor in the middle of the word
3. select backwards few letters by clicking mouse
4. One letter more to the right has been selected

Screen recording with --clean parameter

https://github.com/user-attachments/assets/df0712a1-63de-4231-8d8f-b7c1bb2ccd0a

Expected behaviour

Other editors, input fields and terminals doesn't exhibit this behaviour. They select exactly the text requested to be selected.

I've tried: Notes.app, Terminal.app, Kitty, Alakritty, VSCode/VSCodium, Jetbrains editors, chat apps, various browsers

Screen recording from Notes.app

https://github.com/user-attachments/assets/8b10f823-66a6-46fc-a2cf-31ae5adb1bbb

Version of MacVim

MacVim r182 (Vim 9.1.1887)

MacVim installation method

GitHub releases

Environment

macOS Version: 15.7.2

Logs and stack traces

Vim and MacVim configuration where issue is reproducable

No response

How was MacVim launched?

• [x] by launching MacVim.app in macOS (by using the Dock, Spotlight, or the open command)
• [x] by running mvim/gvim in the terminal

Issue has been tested with clean configuration

• [x] by running mvim --clean (or gvim, supplied by MacVim distribution). You can also use the File → "New Clean Window" menu item within MacVim.
• [x] by running vim --clean (in terminal, supplied by MacVim distribution)
• [x] by running vim --clean (in terminal, other suppliers, e.g. /usr/bin/vim)

[ychin]

Other editors, input fields and terminals doesn't exhibit this behaviour. They select exactly the text requested to be selected.

Vim does not behave like native input text fields. You click on a character to move the cursor there, which would select it. MacVim doesn't try to mimic native text input if it conflicts with how Vim works. You can try to play around with set selection=exclusive but it only works for selecting to the right, not selecting to the left.

Note that the Apple native text input behaves in a way that's a bit more complicated than what you described. It depends if you click on the left half or the right half or a character and macOS will do exclusive/inclusive selection respectively.