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package liner
import (
"unicode"
"github.com/mattn/go-runewidth"
)
// 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,
}
// 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 {
// speed up the common case
if r < 127 {
n++
continue
}
n += runewidth.RuneWidth(r)
}
return n
}
func countMultiLineGlyphs(s []rune, columns int, start int) int {
n := start
for _, r := range s {
if r < 127 {
n++
continue
}
switch runewidth.RuneWidth(r) {
case 0:
case 1:
n++
case 2:
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++
}
}
}
return n
}
func getPrefixGlyphs(s []rune, num int) []rune {
p := 0
for n := 0; n < num && p < len(s); p++ {
// speed up the common case
if s[p] < 127 {
n++
continue
}
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-- {
// speed up the common case
if s[p-1] < 127 {
n++
continue
}
if !unicode.IsOneOf(zeroWidth, s[p-1]) {
n++
}
}
return s[p:]
}
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