Getting/setting mark/cursor position using character index instead of byte index

[Yegappan Lakshmanan]

Hi all,

The getpos(), col() and getcurpos() functions currently return the byte index

in a line. The setpos() and cursor() functions use the byte index to position

the cursor or to set a mark.

The language server protocol uses character index instead of byte index

in a line. I see that the various LSP Vim plugins have created their own

utility functions to convert between the byte index and the character index.

It will be better to extend the built-in function to use character indexes,

so that multiple plugins can use this.

What do you think about enhancing these functions like below?

getpos({expr}, [charcol])

col({expr}, [charcol])

setpos({expr}, {list}, [charcol])

cursor({list}, [charcol])

getcurpos([{winid} [, charcoal]})

In the above functions, if 'charcol' is set to true, then the returned column

number will be a character index. If 'charcol' is false or not specified

(the default), then the returned column number will be a byte index.

Thanks,

Yegappan

[Bram Moolenaar]

Using charidx() requires the string to be passed, so that would be a
complicated workaround.

Instead of adding a 0/1/true/false argument we could add new functions:

getcharpos()
charcol()
setcharpos()
getcursorcharpos()
setcursorcharpos()

It's easier to see that "char" is used, compared to an argument that
doesn't say what it's for.

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[Yegappan Lakshmanan]

Hi Bram,

Another option is to introduce two new functions to convert between

the byte index and the character index in a buffer line:

buf_byteidx(bufnr, lnum, charidx)

buf_charidx(bufnr, lnum, byteidx)

The buf_byteidx() function returns the byte index for the given character

index in the specified line and buf_charidx() does the opposite.

What do you think about this approach?

Thanks,

Yegappan

[Bram Moolenaar]

What is it going to look like? You need this for your plugin, so you
can write the script lines to see how it would work.

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[Yegappan Lakshmanan]

Hi Bram,

On Thu, Jan 7, 2021 at 1:04 PM Bram Moolenaar <Br...@moolenaar.net> wrote:

I have created PR #7648 (https://github.com/vim/vim/pull/7648) to implement

these functions.

Regards,

Yegappan