DockerCLI/cli/command/formatter/displayutils.go

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package formatter
import (
"unicode/utf8"
"golang.org/x/text/width"
)
// charWidth returns the number of horizontal positions a character occupies,
// and is used to account for wide characters when displaying strings.
//
// In a broad sense, wide characters include East Asian Wide, East Asian Full-width,
// (when not in East Asian context) see http://unicode.org/reports/tr11/.
func charWidth(r rune) int {
switch width.LookupRune(r).Kind() {
case width.EastAsianWide, width.EastAsianFullwidth:
return 2
default:
return 1
}
}
// Ellipsis truncates a string to fit within maxDisplayWidth, and appends ellipsis (…).
// For maxDisplayWidth of 1 and lower, no ellipsis is appended.
// For maxDisplayWidth of 1, first char of string will return even if its width > 1.
func Ellipsis(s string, maxDisplayWidth int) string {
if maxDisplayWidth <= 0 {
return ""
}
rs := []rune(s)
if maxDisplayWidth == 1 {
return string(rs[0])
}
byteLen := len(s)
if byteLen == utf8.RuneCountInString(s) {
if byteLen <= maxDisplayWidth {
return s
}
return string(rs[:maxDisplayWidth-1]) + "…"
}
var (
display []int
displayWidth int
)
for _, r := range rs {
cw := charWidth(r)
displayWidth += cw
display = append(display, displayWidth)
}
if displayWidth <= maxDisplayWidth {
return s
}
for i := range display {
if display[i] <= maxDisplayWidth-1 && display[i+1] > maxDisplayWidth-1 {
return string(rs[:i+1]) + "…"
}
}
return s
}