path: root/vendor/github.com/peterh/liner/width.go

package liner

import "unicode"

// These character classes are mostly zero width (when combined).
// A few might not be, depending on the user's font. Fixing this
// is non-trivial, given that some terminals don't support
// ANSI DSR/CPR
var zeroWidth = []*unicode.RangeTable{
    unicode.Mn,
    unicode.Me,
    unicode.Cc,
    unicode.Cf,
}

var doubleWidth = []*unicode.RangeTable{
    unicode.Han,
    unicode.Hangul,
    unicode.Hiragana,
    unicode.Katakana,
}

// countGlyphs considers zero-width characters to be zero glyphs wide,
// and members of Chinese, Japanese, and Korean scripts to be 2 glyphs wide.
func countGlyphs(s []rune) int {
    n := 0
    for _, r := range s {
        switch {
        case unicode.IsOneOf(zeroWidth, r):
        case unicode.IsOneOf(doubleWidth, r):
            n += 2
        default:
            n++
        }
    }
    return n
}

func countMultiLineGlyphs(s []rune, columns int, start int) int {
    n := start
    for _, r := range s {
        switch {
        case unicode.IsOneOf(zeroWidth, r):
        case unicode.IsOneOf(doubleWidth, r):
            n += 2
            // no room for a 2-glyphs-wide char in the ending
            // so skip a column and display it at the beginning
            if n%columns == 1 {
                n++
            }
        default:
            n++
        }
    }
    return n
}

func getPrefixGlyphs(s []rune, num int) []rune {
    p := 0
    for n := 0; n < num && p < len(s); p++ {
        if !unicode.IsOneOf(zeroWidth, s[p]) {
            n++
        }
    }
    for p < len(s) && unicode.IsOneOf(zeroWidth, s[p]) {
        p++
    }
    return s[:p]
}

func getSuffixGlyphs(s []rune, num int) []rune {
    p := len(s)
    for n := 0; n < num && p > 0; p-- {
        if !unicode.IsOneOf(zeroWidth, s[p-1]) {
            n++
        }
    }
    return s[p:]
}