elvish/edit/wcwidth.go

package edit

import (
	"sort"
	"strings"
)

// Taken from http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c (public domain)
var combining = [][2]rune{
	{0x0300, 0x036F}, {0x0483, 0x0486}, {0x0488, 0x0489},
	{0x0591, 0x05BD}, {0x05BF, 0x05BF}, {0x05C1, 0x05C2},
	{0x05C4, 0x05C5}, {0x05C7, 0x05C7}, {0x0600, 0x0603},
	{0x0610, 0x0615}, {0x064B, 0x065E}, {0x0670, 0x0670},
	{0x06D6, 0x06E4}, {0x06E7, 0x06E8}, {0x06EA, 0x06ED},
	{0x070F, 0x070F}, {0x0711, 0x0711}, {0x0730, 0x074A},
	{0x07A6, 0x07B0}, {0x07EB, 0x07F3}, {0x0901, 0x0902},
	{0x093C, 0x093C}, {0x0941, 0x0948}, {0x094D, 0x094D},
	{0x0951, 0x0954}, {0x0962, 0x0963}, {0x0981, 0x0981},
	{0x09BC, 0x09BC}, {0x09C1, 0x09C4}, {0x09CD, 0x09CD},
	{0x09E2, 0x09E3}, {0x0A01, 0x0A02}, {0x0A3C, 0x0A3C},
	{0x0A41, 0x0A42}, {0x0A47, 0x0A48}, {0x0A4B, 0x0A4D},
	{0x0A70, 0x0A71}, {0x0A81, 0x0A82}, {0x0ABC, 0x0ABC},
	{0x0AC1, 0x0AC5}, {0x0AC7, 0x0AC8}, {0x0ACD, 0x0ACD},
	{0x0AE2, 0x0AE3}, {0x0B01, 0x0B01}, {0x0B3C, 0x0B3C},
	{0x0B3F, 0x0B3F}, {0x0B41, 0x0B43}, {0x0B4D, 0x0B4D},
	{0x0B56, 0x0B56}, {0x0B82, 0x0B82}, {0x0BC0, 0x0BC0},
	{0x0BCD, 0x0BCD}, {0x0C3E, 0x0C40}, {0x0C46, 0x0C48},
	{0x0C4A, 0x0C4D}, {0x0C55, 0x0C56}, {0x0CBC, 0x0CBC},
	{0x0CBF, 0x0CBF}, {0x0CC6, 0x0CC6}, {0x0CCC, 0x0CCD},
	{0x0CE2, 0x0CE3}, {0x0D41, 0x0D43}, {0x0D4D, 0x0D4D},
	{0x0DCA, 0x0DCA}, {0x0DD2, 0x0DD4}, {0x0DD6, 0x0DD6},
	{0x0E31, 0x0E31}, {0x0E34, 0x0E3A}, {0x0E47, 0x0E4E},
	{0x0EB1, 0x0EB1}, {0x0EB4, 0x0EB9}, {0x0EBB, 0x0EBC},
	{0x0EC8, 0x0ECD}, {0x0F18, 0x0F19}, {0x0F35, 0x0F35},
	{0x0F37, 0x0F37}, {0x0F39, 0x0F39}, {0x0F71, 0x0F7E},
	{0x0F80, 0x0F84}, {0x0F86, 0x0F87}, {0x0F90, 0x0F97},
	{0x0F99, 0x0FBC}, {0x0FC6, 0x0FC6}, {0x102D, 0x1030},
	{0x1032, 0x1032}, {0x1036, 0x1037}, {0x1039, 0x1039},
	{0x1058, 0x1059}, {0x1160, 0x11FF}, {0x135F, 0x135F},
	{0x1712, 0x1714}, {0x1732, 0x1734}, {0x1752, 0x1753},
	{0x1772, 0x1773}, {0x17B4, 0x17B5}, {0x17B7, 0x17BD},
	{0x17C6, 0x17C6}, {0x17C9, 0x17D3}, {0x17DD, 0x17DD},
	{0x180B, 0x180D}, {0x18A9, 0x18A9}, {0x1920, 0x1922},
	{0x1927, 0x1928}, {0x1932, 0x1932}, {0x1939, 0x193B},
	{0x1A17, 0x1A18}, {0x1B00, 0x1B03}, {0x1B34, 0x1B34},
	{0x1B36, 0x1B3A}, {0x1B3C, 0x1B3C}, {0x1B42, 0x1B42},
	{0x1B6B, 0x1B73}, {0x1DC0, 0x1DCA}, {0x1DFE, 0x1DFF},
	{0x200B, 0x200F}, {0x202A, 0x202E}, {0x2060, 0x2063},
	{0x206A, 0x206F}, {0x20D0, 0x20EF}, {0x302A, 0x302F},
	{0x3099, 0x309A}, {0xA806, 0xA806}, {0xA80B, 0xA80B},
	{0xA825, 0xA826}, {0xFB1E, 0xFB1E}, {0xFE00, 0xFE0F},
	{0xFE20, 0xFE23}, {0xFEFF, 0xFEFF}, {0xFFF9, 0xFFFB},
	{0x10A01, 0x10A03}, {0x10A05, 0x10A06}, {0x10A0C, 0x10A0F},
	{0x10A38, 0x10A3A}, {0x10A3F, 0x10A3F}, {0x1D167, 0x1D169},
	{0x1D173, 0x1D182}, {0x1D185, 0x1D18B}, {0x1D1AA, 0x1D1AD},
	{0x1D242, 0x1D244}, {0xE0001, 0xE0001}, {0xE0020, 0xE007F},
	{0xE0100, 0xE01EF},
}

func isCombining(r rune) bool {
	n := len(combining)
	i := sort.Search(n, func(i int) bool { return r <= combining[i][1] })
	return i < n && r >= combining[i][0]
}

// WcWidth returns the width of a rune when displayed on the terminal.
func WcWidth(r rune) int {
	switch {
	case r == 0:
		return 0
	case r < 32 || (0x7f <= r && r < 0xa0): // Control character
		return -1
	case isCombining(r):
		return 0
	}

	if r >= 0x1100 &&
		(r <= 0x115f || /* Hangul Jamo init. consonants */
			r == 0x2329 || r == 0x232a ||
			(r >= 0x2e80 && r <= 0xa4cf &&
				r != 0x303f) || /* CJK ... Yi */
			(r >= 0xac00 && r <= 0xd7a3) || /* Hangul Syllables */
			(r >= 0xf900 && r <= 0xfaff) || /* CJK Compatibility Ideographs */
			(r >= 0xfe10 && r <= 0xfe19) || /* Vertical forms */
			(r >= 0xfe30 && r <= 0xfe6f) || /* CJK Compatibility Forms */
			(r >= 0xff00 && r <= 0xff60) || /* Fullwidth Forms */
			(r >= 0xffe0 && r <= 0xffe6) ||
			(r >= 0x20000 && r <= 0x2fffd) ||
			(r >= 0x30000 && r <= 0x3fffd)) {
		return 2
	}
	return 1
}

// WcWidths returns the width of a string when displayed on the terminal,
// assuming no soft line breaks.
func WcWidths(s string) (w int) {
	for _, r := range s {
		w += WcWidth(r)
	}
	return
}

// TrimWcWidth trims the string s so that it has a width of at most wmax.
func TrimWcWidth(s string, wmax int) string {
	w := 0
	for i, r := range s {
		w += WcWidth(r)
		if w > wmax {
			return s[:i]
		}
	}
	return s
}

// ForceWcWidth forces the string s to the given display width by trimming and
// padding.
func ForceWcWidth(s string, width int) string {
	w := 0
	for i, r := range s {
		w0 := WcWidth(r)
		w += w0
		if w > width {
			w -= w0
			s = s[:i]
			break
		}
	}
	return s + strings.Repeat(" ", width-w)
}