How to efficiently highlight a region given a START and END position expressed as line_nr, col_nr?

Question

Say that I want to highlight a region expressed in terms of two coordinates of the form (line, column), e.g. C1 = (l1, c1) to C2 = (l2, c2).

I read :h matchaddpos() but it seems that you can only specify entire lines or single characters to highlight, or you can express a range through starting position + length, which would lead to not very readable solutions, although the latest could be interesting as it would require the definition of a distance in the metric space built on the buffer’s coordinates set.

:h matchadd() requires a pattern but I am not sure how should I specify patterns for ranges expressed in terms of coordinates of the form (line, column).

Answer 1

To match from line 2 column 3 to line 4 column 5 (not included) you could use the following regular expression:

\%2l\%3c\_.*\%4l\%5c

• \%2l match only on line 2
• \%3c match only right before character 3
• \_.* match any list of characters including new line

More information with:

• :h /\%c
• :h /\%l

You could then:

:call matchadd(group, '\%2l\%3c\_.*\%4l\%5c')

Where group is an highlighting group.

E.g:

:call matchadd("ErrorMsg", '\%2l\%3c\_.*\%4l\%5c')

Answer 2

You could use text properties, with the added benefit of not having to do as much bookkeeping to keep the highlight in place:

call prop_type_add('number', {'highlight': 'Constant'})
call prop_add(11, 12, #{type: 'number', end_lnum: 12, end_col: 13})

Answer 3

This could be a solution that, if on the one hand seems efficient due to the utilization of matchaddpos() instead of matchadd(), on the other hand it contains a number of for loops:

def BuildMatchPattern(l0: number, c0: number, l1: number, c1: number): list<any>
    # Say that we yanked from line 23, col 15 to line 26, col 19.
    # This function return the following list [[23, 15], 24, 25, [26, 19]]
    var match_pattern = []
    # Yank on one line
    if l0 == l1
        for c in range(c0, c1)
            add(match_pattern, [l0, c])
        endfor
    else
        # Yank on two consecutive lines
        # First line
        for c in range(c0, col('$'))
            add(match_pattern, [l0, c])
        endfor
        # Second line
        for c in range(1, c1)
            add(match_pattern, [l1, c])
        endfor
    endif

    # Yanked more than two lines (you must get the whole intermediate lines)
    if l1 - l0 >= 2
        for l in range(l0 + 1, l1 - 1)
            add(match_pattern, l)
        endfor
    endif
    return match_pattern
enddef

    matchaddpos('Visual', BuildMatchPattern(l0, c0, l1, c1))