ZyX wrote:
> Given recent discussion around matchaddpos() and the fact that
> converting virtual column to byte offset has a larger variety of use
> cases (I personally needed this to get <C-v>-selected block without
> altering marks, registers, cursor position, etc) I propose the new
> function colnr():
>
> colnr :: (string, number, options) -> col
>
> This function accepts number: generic index and translates it to byte
> offset according to given options which may be one of the following:
>
> 1. `'col'`: returns `number` or length of the string plus one,
> whichever is smaller. Alias to {'unicode': 0, 'tabstop': 1,
> 'fixed_width_tab': 1}
> 2. `'codepoint'`: returns byte offset of Unicode codepoint with index
> given as `number` (here and below index starts from 1). Alias to
> {'tabstop': 1, 'fixed_width_tab': 1, 'ambiwidth': 'single',
> 'fullwidth_len': 1, 'diacritics_len': 1, 'invalid_unicode': 'error'}.
> Is opposite of `strchars()`.
> 3. `'virtcol'`: alias to {} which is the same as {'tabstop': &tabstop,
> 'fixed_width_tab': 0, 'ambiwidth': &ambiwidth, 'fullwidth_len': 2,
> 'diacritics_len': 0, 'diacritics_start_len': 1, 'unicode': 1,
> 'invalid_unicode': 'strtrans'}.
> 4. A dictionary with the following keys:
>
> - tabstop: effective value of &tabstop. All defaults are listed in 3.
> - fixed_width_tab: if non-zero, makes every tab be assumed to occupy
> `tabstop` columns.
> - ambiwidth: effective value of &ambiwidth.
> - fullwidth_len: number of indexes fullwidth characters occupy.
> - diacritics_len: number of indexes diacritics characters occupy.
> - diacritics_start_len: length of the one diacritic character that is at
> the start of the string.
> - unicode: if non-zero, recognizes one unicode character as occupying one
> index. Disables `ambiwidth`, `fullwidth_len`, `diacritics_len`,
> `diacritics_start_len` and `invalid_unicode` options.
It's probably better to use 'encoding', some users will have other
encodings than Unicode, e.g. a compiler in Japan or China would output
double-byte characters.
> - invalid_unicode: determines how to treat bytes that are not valid
> unicode. Valid values are
> - strtrans: use length of the `strtrans` result.
> - error: fail with error, return zero.
> - single: treat as occupying one index.
>
> Use-cases:
>
> 1. Transform screen column to byte offset:
>
> echo colnr("\ta", 2, 'virtcol') " Returns 1 since 2 is in the middle
> of the tab
> 2. Transform screen column reported by some compiler to byte offset:
>
> echo colnr(string, idx, {'tabstop': 8})
> 3. Transform screen column reported by some compiler that only knows ASCII
> and still things 1 character == 1 byte:
>
> echo colnr(string, idx, {'tabstop': 8, 'unicode': 0})
> 4. Transform index of unicode() string reported by some python program:
>
> echo colnr(string, idx + 1, 'codepoint')
> 5. Allow configuring transformer without :if branches: allow byte index
>
> echo colnr(string, idx, 'col') " Will echo idx most of time
Sounds useful. It's going to be a lot of work to implement though.
Especially with all the options.
I would suggest first writing the documentation, thus explaining to a
Vim script programmer how to use it, to find out if it's not too
difficult to understand.
--
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"So what do you think about this Mad Cow Disease?"
The other replies: "That doesn't concern me. I'm a helicopter."
/// Bram Moolenaar -- [email protected] -- http://www.Moolenaar.net \\\
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