support wide characters in the editor

go.mod

@@ -19,17 +19,19 @@ require (
 	github.com/imdario/mergo v0.3.11
 	github.com/integrii/flaggy v1.4.0
 	github.com/jesseduffield/go-git/v5 v5.1.2-0.20201006095850-341962be15a4
-	github.com/jesseduffield/gocui v0.3.1-0.20201010224802-8a6768078fd7
+	github.com/jesseduffield/gocui v0.3.1-0.20210208224444-2eecee85583d
 	github.com/jesseduffield/termbox-go v0.0.0-20200823212418-a2289ed6aafe
 	github.com/jesseduffield/yaml v2.1.0+incompatible
 	github.com/kardianos/osext v0.0.0-20190222173326-2bc1f35cddc0
 	github.com/konsorten/go-windows-terminal-sequences v1.0.2 // indirect
 	github.com/kylelemons/godebug v1.1.0 // indirect
 	github.com/mattn/go-colorable v0.1.7 // indirect
-	github.com/mattn/go-runewidth v0.0.9
+	github.com/mattn/go-runewidth v0.0.10
 	github.com/mgutz/str v1.2.0
+	github.com/nsf/termbox-go v0.0.0-20210114135735-d04385b850e8 // indirect
 	github.com/onsi/ginkgo v1.10.3 // indirect
 	github.com/onsi/gomega v1.7.1 // indirect
+	github.com/rivo/uniseg v0.2.0 // indirect
 	github.com/sahilm/fuzzy v0.1.0
 	github.com/sirupsen/logrus v1.4.2
 	github.com/spkg/bom v0.0.0-20160624110644-59b7046e48ad

go.sum

@@ -65,8 +65,12 @@ github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99 h1:BQSFePA1RWJOl
 github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99/go.mod h1:1lJo3i6rXxKeerYnT8Nvf0QmHCRC1n8sfWVwXF2Frvo=
 github.com/jesseduffield/go-git/v5 v5.1.2-0.20201006095850-341962be15a4 h1:GOQrmaE8i+KEdB8NzAegKYd4tPn/inM0I1uo0NXFerg=
 github.com/jesseduffield/go-git/v5 v5.1.2-0.20201006095850-341962be15a4/go.mod h1:nGNEErzf+NRznT+N2SWqmHnDnF9aLgANB1CUNEan09o=
+github.com/jesseduffield/gocui v0.3.1-0.20161105104656-d666c9f652af h1:9ZI/QyVOerYYeqMt4svycU2Lz0WvxNHCpHHbsFsi/oA=
+github.com/jesseduffield/gocui v0.3.1-0.20161105104656-d666c9f652af/go.mod h1:2RtZznzYKt8RLRwvFiSkXjU0Ei8WwHdubgnlaYH47dw=
 github.com/jesseduffield/gocui v0.3.1-0.20201010224802-8a6768078fd7 h1:K3MGrjmpPtIhfXmKh/zsIF0CdmNKOkjpIwcUfAa/J2A=
 github.com/jesseduffield/gocui v0.3.1-0.20201010224802-8a6768078fd7/go.mod h1:2RtZznzYKt8RLRwvFiSkXjU0Ei8WwHdubgnlaYH47dw=
+github.com/jesseduffield/gocui v0.3.1-0.20210208224444-2eecee85583d h1:Jto9W9w8CFwZiAYXa7LsHDEOb5cKCA1f5LOL1A3jva4=
+github.com/jesseduffield/gocui v0.3.1-0.20210208224444-2eecee85583d/go.mod h1:2RtZznzYKt8RLRwvFiSkXjU0Ei8WwHdubgnlaYH47dw=
 github.com/jesseduffield/termbox-go v0.0.0-20200823212418-a2289ed6aafe h1:qsVhCf2RFyyKIUe/+gJblbCpXMUki9rZrHuEctg6M/E=
 github.com/jesseduffield/termbox-go v0.0.0-20200823212418-a2289ed6aafe/go.mod h1:anMibpZtqNxjDbxrcDEAwSdaJ37vyUeM1f/M4uekib4=
 github.com/jesseduffield/yaml v2.1.0+incompatible h1:HWQJ1gIv2zHKbDYNp0Jwjlj24K8aqpFHnMCynY1EpmE=
@@ -103,12 +107,16 @@ github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHX
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
 github.com/mattn/go-runewidth v0.0.9 h1:Lm995f3rfxdpd6TSmuVCHVb/QhupuXlYr8sCI/QdE+0=
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
+github.com/mattn/go-runewidth v0.0.10 h1:CoZ3S2P7pvtP45xOtBw+/mDL2z0RKI576gSkzRRpdGg=
+github.com/mattn/go-runewidth v0.0.10/go.mod h1:RAqKPSqVFrSLVXbA8x7dzmKdmGzieGRCM46jaSJTDAk=
 github.com/mgutz/str v1.2.0 h1:4IzWSdIz9qPQWLfKZ0rJcV0jcUDpxvP4JVZ4GXQyvSw=
 github.com/mgutz/str v1.2.0/go.mod h1:w1v0ofgLaJdoD0HpQ3fycxKD1WtxpjSo151pK/31q6w=
 github.com/mitchellh/go-homedir v1.1.0 h1:lukF9ziXFxDFPkA1vsr5zpc1XuPDn/wFntq5mG+4E0Y=
 github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e h1:fD57ERR4JtEqsWbfPhv4DMiApHyliiK5xCTNVSPiaAs=
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e/go.mod h1:zD1mROLANZcx1PVRCS0qkT7pwLkGfwJo4zjcN/Tysno=
+github.com/nsf/termbox-go v0.0.0-20210114135735-d04385b850e8 h1:3vzIuru1svOK2sXlg4XcrO3KkGRneIejmfQfR+ptSW8=
+github.com/nsf/termbox-go v0.0.0-20210114135735-d04385b850e8/go.mod h1:T0cTdVuOwf7pHQNtfhnEbzHbcNyCEcVU4YPpouCbVxo=
 github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
 github.com/onsi/ginkgo v1.10.3 h1:OoxbjfXVZyod1fmWYhI7SEyaD8B00ynP3T+D5GiyHOY=
 github.com/onsi/ginkgo v1.10.3/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
@@ -118,6 +126,10 @@ github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rivo/uniseg v0.1.0 h1:+2KBaVoUmb9XzDsrx/Ct0W/EYOSFf/nWTauy++DprtY=
+github.com/rivo/uniseg v0.1.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
+github.com/rivo/uniseg v0.2.0 h1:S1pD9weZBuJdFmowNwbpi7BJ8TNftyUImj/0WQi72jY=
+github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/sahilm/fuzzy v0.1.0 h1:FzWGaw2Opqyu+794ZQ9SYifWv2EIXpwP4q8dY1kDAwI=
 github.com/sahilm/fuzzy v0.1.0/go.mod h1:VFvziUEIMCrT6A6tw2RFIXPXXmzXbOsSHF0DOI8ZK9Y=
 github.com/sergi/go-diff v1.1.0 h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=

vendor/github.com/jesseduffield/gocui/edit.go

@@ -343,17 +343,18 @@ func (v *View) writeRune(x, y int, ch rune) error {
 	}
 
 	olen := len(v.lines[y])
+	w := runewidth.RuneWidth(ch)
 
 	var s []cell
 	if x >= len(v.lines[y]) {
-		s = make([]cell, x-len(v.lines[y])+1)
+		s = make([]cell, x-len(v.lines[y])+w)
 	} else if !v.Overwrite {
-		s = make([]cell, 1)
+		s = make([]cell, w)
 	}
 	v.lines[y] = append(v.lines[y], s...)
 
-	if !v.Overwrite || (v.Overwrite && x >= olen-1) {
+	if !v.Overwrite || (v.Overwrite && x >= olen-w) {
-		copy(v.lines[y][x+1:], v.lines[y][x:])
+		copy(v.lines[y][x+w:], v.lines[y][x:])
 	}
 	v.lines[y][x] = cell{
 		fgColor: v.FgColor,
@@ -361,6 +362,14 @@ func (v *View) writeRune(x, y int, ch rune) error {
 		chr:     ch,
 	}
 
+	for i := 1; i < w; i++ {
+		v.lines[y][x+i] = cell{
+			fgColor: v.FgColor,
+			bgColor: v.BgColor,
+			chr:     '\x00',
+		}
+	}
+
 	return nil
 }
 
@@ -384,7 +393,7 @@ func (v *View) deleteRune(x, y int) (int, error) {
 		w := runewidth.RuneWidth(v.lines[y][i].chr)
 		tw += w
 		if tw > x {
-			v.lines[y] = append(v.lines[y][:i], v.lines[y][i+1:]...)
+			v.lines[y] = append(v.lines[y][:i], v.lines[y][i+w:]...)
 			return w, nil
 		}
 

vendor/github.com/mattn/go-runewidth/go.mod

@@ -1,3 +1,5 @@
 module github.com/mattn/go-runewidth
 
 go 1.9
+
+require github.com/rivo/uniseg v0.1.0

vendor/github.com/mattn/go-runewidth/go.sum

@@ -0,0 +1,2 @@
+github.com/rivo/uniseg v0.1.0 h1:+2KBaVoUmb9XzDsrx/Ct0W/EYOSFf/nWTauy++DprtY=
+github.com/rivo/uniseg v0.1.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=

vendor/github.com/mattn/go-runewidth/runewidth.go

@@ -2,6 +2,8 @@ package runewidth
 
 import (
 	"os"
+
+	"github.com/rivo/uniseg"
 )
 
 //go:generate go run script/generate.go
@@ -10,9 +12,6 @@ var (
 	// EastAsianWidth will be set true if the current locale is CJK
 	EastAsianWidth bool
 
-	// ZeroWidthJoiner is flag to set to use UTR#51 ZWJ
-	ZeroWidthJoiner bool
-
 	// DefaultCondition is a condition in current locale
 	DefaultCondition = &Condition{}
 )
@@ -30,7 +29,6 @@ func handleEnv() {
 	}
 	// update DefaultCondition
 	DefaultCondition.EastAsianWidth = EastAsianWidth
-	DefaultCondition.ZeroWidthJoiner = ZeroWidthJoiner
 }
 
 type interval struct {
@@ -85,15 +83,13 @@ var nonprint = table{
 
 // Condition have flag EastAsianWidth whether the current locale is CJK or not.
 type Condition struct {
-	EastAsianWidth  bool
+	EastAsianWidth bool
-	ZeroWidthJoiner bool
 }
 
 // NewCondition return new instance of Condition which is current locale.
 func NewCondition() *Condition {
 	return &Condition{
-		EastAsianWidth:  EastAsianWidth,
+		EastAsianWidth: EastAsianWidth,
-		ZeroWidthJoiner: ZeroWidthJoiner,
 	}
 }
 
@@ -110,38 +106,20 @@ func (c *Condition) RuneWidth(r rune) int {
 	}
 }
 
-func (c *Condition) stringWidth(s string) (width int) {
-	for _, r := range []rune(s) {
-		width += c.RuneWidth(r)
-	}
-	return width
-}
-
-func (c *Condition) stringWidthZeroJoiner(s string) (width int) {
-	r1, r2 := rune(0), rune(0)
-	for _, r := range []rune(s) {
-		if r == 0xFE0E || r == 0xFE0F {
-			continue
-		}
-		w := c.RuneWidth(r)
-		if r2 == 0x200D && inTables(r, emoji) && inTables(r1, emoji) {
-			if width < w {
-				width = w
-			}
-		} else {
-			width += w
-		}
-		r1, r2 = r2, r
-	}
-	return width
-}
-
 // StringWidth return width as you can see
 func (c *Condition) StringWidth(s string) (width int) {
-	if c.ZeroWidthJoiner {
+	g := uniseg.NewGraphemes(s)
-		return c.stringWidthZeroJoiner(s)
+	for g.Next() {
+		var chWidth int
+		for _, r := range g.Runes() {
+			chWidth = c.RuneWidth(r)
+			if chWidth > 0 {
+				break // Our best guess at this point is to use the width of the first non-zero-width rune.
+			}
+		}
+		width += chWidth
 	}
-	return c.stringWidth(s)
+	return
 }
 
 // Truncate return string truncated with w cells
@@ -149,19 +127,25 @@ func (c *Condition) Truncate(s string, w int, tail string) string {
 	if c.StringWidth(s) <= w {
 		return s
 	}
-	r := []rune(s)
+	w -= c.StringWidth(tail)
-	tw := c.StringWidth(tail)
+	var width int
-	w -= tw
+	pos := len(s)
-	width := 0
+	g := uniseg.NewGraphemes(s)
-	i := 0
+	for g.Next() {
-	for ; i < len(r); i++ {
+		var chWidth int
-		cw := c.RuneWidth(r[i])
+		for _, r := range g.Runes() {
-		if width+cw > w {
+			chWidth = c.RuneWidth(r)
+			if chWidth > 0 {
+				break // See StringWidth() for details.
+			}
+		}
+		if width+chWidth > w {
+			pos, _ = g.Positions()
 			break
 		}
-		width += cw
+		width += chWidth
 	}
-	return string(r[0:i]) + tail
+	return s[:pos] + tail
 }
 
 // Wrap return string wrapped with w cells
@@ -169,7 +153,7 @@ func (c *Condition) Wrap(s string, w int) string {
 	width := 0
 	out := ""
 	for _, r := range []rune(s) {
-		cw := RuneWidth(r)
+		cw := c.RuneWidth(r)
 		if r == '\n' {
 			out += string(r)
 			width = 0

vendor/github.com/rivo/uniseg/LICENSE.txt

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2019 Oliver Kuederle
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

vendor/github.com/rivo/uniseg/README.md

@@ -0,0 +1,62 @@
+# Unicode Text Segmentation for Go
+
+[![Godoc Reference](https://img.shields.io/badge/godoc-reference-blue.svg)](https://godoc.org/github.com/rivo/uniseg)
+[![Go Report](https://img.shields.io/badge/go%20report-A%2B-brightgreen.svg)](https://goreportcard.com/report/github.com/rivo/uniseg)
+
+This Go package implements Unicode Text Segmentation according to [Unicode Standard Annex #29](http://unicode.org/reports/tr29/) (Unicode version 12.0.0).
+
+At this point, only the determination of grapheme cluster boundaries is implemented.
+
+## Background
+
+In Go, [strings are read-only slices of bytes](https://blog.golang.org/strings). They can be turned into Unicode code points using the `for` loop or by casting: `[]rune(str)`. However, multiple code points may be combined into one user-perceived character or what the Unicode specification calls "grapheme cluster". Here are some examples:
+
+|String|Bytes (UTF-8)|Code points (runes)|Grapheme clusters|
+|-|-|-|-|
+|Käse|6 bytes: `4b 61 cc 88 73 65`|5 code points: `4b 61 308 73 65`|4 clusters: `[4b],[61 308],[73],[65]`|
+|🏳️‍🌈|14 bytes: `f0 9f 8f b3 ef b8 8f e2 80 8d f0 9f 8c 88`|4 code points: `1f3f3 fe0f 200d 1f308`|1 cluster: `[1f3f3 fe0f 200d 1f308]`|
+|🇩🇪|8 bytes: `f0 9f 87 a9 f0 9f 87 aa`|2 code points: `1f1e9 1f1ea`|1 cluster: `[1f1e9 1f1ea]`|
+
+This package provides a tool to iterate over these grapheme clusters. This may be used to determine the number of user-perceived characters, to split strings in their intended places, or to extract individual characters which form a unit.
+
+## Installation
+
+```bash
+go get github.com/rivo/uniseg
+```
+
+## Basic Example
+
+```go
+package uniseg
+
+import (
+	"fmt"
+
+	"github.com/rivo/uniseg"
+)
+
+func main() {
+	gr := uniseg.NewGraphemes("👍🏼!")
+	for gr.Next() {
+		fmt.Printf("%x ", gr.Runes())
+	}
+	// Output: [1f44d 1f3fc] [21]
+}
+```
+
+## Documentation
+
+Refer to https://godoc.org/github.com/rivo/uniseg for the package's documentation.
+
+## Dependencies
+
+This package does not depend on any packages outside the standard library.
+
+## Your Feedback
+
+Add your issue here on GitHub. Feel free to get in touch if you have any questions.
+
+## Version
+
+Version tags will be introduced once Golang modules are official. Consider this version 0.1.

vendor/github.com/rivo/uniseg/doc.go

@@ -0,0 +1,8 @@
+/*
+Package uniseg implements Unicode Text Segmentation according to Unicode
+Standard Annex #29 (http://unicode.org/reports/tr29/).
+
+At this point, only the determination of grapheme cluster boundaries is
+implemented.
+*/
+package uniseg

vendor/github.com/rivo/uniseg/go.mod

@@ -0,0 +1,3 @@
+module github.com/rivo/uniseg
+
+go 1.12

vendor/github.com/rivo/uniseg/grapheme.go

@@ -0,0 +1,268 @@
+package uniseg
+
+import "unicode/utf8"
+
+// The states of the grapheme cluster parser.
+const (
+	grAny = iota
+	grCR
+	grControlLF
+	grL
+	grLVV
+	grLVTT
+	grPrepend
+	grExtendedPictographic
+	grExtendedPictographicZWJ
+	grRIOdd
+	grRIEven
+)
+
+// The grapheme cluster parser's breaking instructions.
+const (
+	grNoBoundary = iota
+	grBoundary
+)
+
+// The grapheme cluster parser's state transitions. Maps (state, property) to
+// (new state, breaking instruction, rule number). The breaking instruction
+// always refers to the boundary between the last and next code point.
+//
+// This map is queried as follows:
+//
+//   1. Find specific state + specific property. Stop if found.
+//   2. Find specific state + any property.
+//   3. Find any state + specific property.
+//   4. If only (2) or (3) (but not both) was found, stop.
+//   5. If both (2) and (3) were found, use state and breaking instruction from
+//      the transition with the lower rule number, prefer (3) if rule numbers
+//      are equal. Stop.
+//   6. Assume grAny and grBoundary.
+var grTransitions = map[[2]int][3]int{
+	// GB5
+	{grAny, prCR}:      {grCR, grBoundary, 50},
+	{grAny, prLF}:      {grControlLF, grBoundary, 50},
+	{grAny, prControl}: {grControlLF, grBoundary, 50},
+
+	// GB4
+	{grCR, prAny}:        {grAny, grBoundary, 40},
+	{grControlLF, prAny}: {grAny, grBoundary, 40},
+
+	// GB3.
+	{grCR, prLF}: {grAny, grNoBoundary, 30},
+
+	// GB6.
+	{grAny, prL}: {grL, grBoundary, 9990},
+	{grL, prL}:   {grL, grNoBoundary, 60},
+	{grL, prV}:   {grLVV, grNoBoundary, 60},
+	{grL, prLV}:  {grLVV, grNoBoundary, 60},
+	{grL, prLVT}: {grLVTT, grNoBoundary, 60},
+
+	// GB7.
+	{grAny, prLV}: {grLVV, grBoundary, 9990},
+	{grAny, prV}:  {grLVV, grBoundary, 9990},
+	{grLVV, prV}:  {grLVV, grNoBoundary, 70},
+	{grLVV, prT}:  {grLVTT, grNoBoundary, 70},
+
+	// GB8.
+	{grAny, prLVT}: {grLVTT, grBoundary, 9990},
+	{grAny, prT}:   {grLVTT, grBoundary, 9990},
+	{grLVTT, prT}:  {grLVTT, grNoBoundary, 80},
+
+	// GB9.
+	{grAny, prExtend}: {grAny, grNoBoundary, 90},
+	{grAny, prZWJ}:    {grAny, grNoBoundary, 90},
+
+	// GB9a.
+	{grAny, prSpacingMark}: {grAny, grNoBoundary, 91},
+
+	// GB9b.
+	{grAny, prPreprend}: {grPrepend, grBoundary, 9990},
+	{grPrepend, prAny}:  {grAny, grNoBoundary, 92},
+
+	// GB11.
+	{grAny, prExtendedPictographic}:                     {grExtendedPictographic, grBoundary, 9990},
+	{grExtendedPictographic, prExtend}:                  {grExtendedPictographic, grNoBoundary, 110},
+	{grExtendedPictographic, prZWJ}:                     {grExtendedPictographicZWJ, grNoBoundary, 110},
+	{grExtendedPictographicZWJ, prExtendedPictographic}: {grExtendedPictographic, grNoBoundary, 110},
+
+	// GB12 / GB13.
+	{grAny, prRegionalIndicator}:    {grRIOdd, grBoundary, 9990},
+	{grRIOdd, prRegionalIndicator}:  {grRIEven, grNoBoundary, 120},
+	{grRIEven, prRegionalIndicator}: {grRIOdd, grBoundary, 120},
+}
+
+// Graphemes implements an iterator over Unicode extended grapheme clusters,
+// specified in the Unicode Standard Annex #29. Grapheme clusters correspond to
+// "user-perceived characters". These characters often consist of multiple
+// code points (e.g. the "woman kissing woman" emoji consists of 8 code points:
+// woman + ZWJ + heavy black heart (2 code points) + ZWJ + kiss mark + ZWJ +
+// woman) and the rules described in Annex #29 must be applied to group those
+// code points into clusters perceived by the user as one character.
+type Graphemes struct {
+	// The code points over which this class iterates.
+	codePoints []rune
+
+	// The (byte-based) indices of the code points into the original string plus
+	// len(original string). Thus, len(indices) = len(codePoints) + 1.
+	indices []int
+
+	// The current grapheme cluster to be returned. These are indices into
+	// codePoints/indices. If start == end, we either haven't started iterating
+	// yet (0) or the iteration has already completed (1).
+	start, end int
+
+	// The index of the next code point to be parsed.
+	pos int
+
+	// The current state of the code point parser.
+	state int
+}
+
+// NewGraphemes returns a new grapheme cluster iterator.
+func NewGraphemes(s string) *Graphemes {
+	l := utf8.RuneCountInString(s)
+	codePoints := make([]rune, l)
+	indices := make([]int, l+1)
+	i := 0
+	for pos, r := range s {
+		codePoints[i] = r
+		indices[i] = pos
+		i++
+	}
+	indices[l] = len(s)
+	g := &Graphemes{
+		codePoints: codePoints,
+		indices:    indices,
+	}
+	g.Next() // Parse ahead.
+	return g
+}
+
+// Next advances the iterator by one grapheme cluster and returns false if no
+// clusters are left. This function must be called before the first cluster is
+// accessed.
+func (g *Graphemes) Next() bool {
+	g.start = g.end
+
+	// The state transition gives us a boundary instruction BEFORE the next code
+	// point so we always need to stay ahead by one code point.
+
+	// Parse the next code point.
+	for g.pos <= len(g.codePoints) {
+		// GB2.
+		if g.pos == len(g.codePoints) {
+			g.end = g.pos
+			g.pos++
+			break
+		}
+
+		// Determine the property of the next character.
+		nextProperty := property(g.codePoints[g.pos])
+		g.pos++
+
+		// Find the applicable transition.
+		var boundary bool
+		transition, ok := grTransitions[[2]int{g.state, nextProperty}]
+		if ok {
+			// We have a specific transition. We'll use it.
+			g.state = transition[0]
+			boundary = transition[1] == grBoundary
+		} else {
+			// No specific transition found. Try the less specific ones.
+			transAnyProp, okAnyProp := grTransitions[[2]int{g.state, prAny}]
+			transAnyState, okAnyState := grTransitions[[2]int{grAny, nextProperty}]
+			if okAnyProp && okAnyState {
+				// Both apply. We'll use a mix (see comments for grTransitions).
+				g.state = transAnyState[0]
+				boundary = transAnyState[1] == grBoundary
+				if transAnyProp[2] < transAnyState[2] {
+					g.state = transAnyProp[0]
+					boundary = transAnyProp[1] == grBoundary
+				}
+			} else if okAnyProp {
+				// We only have a specific state.
+				g.state = transAnyProp[0]
+				boundary = transAnyProp[1] == grBoundary
+				// This branch will probably never be reached because okAnyState will
+				// always be true given the current transition map. But we keep it here
+				// for future modifications to the transition map where this may not be
+				// true anymore.
+			} else if okAnyState {
+				// We only have a specific property.
+				g.state = transAnyState[0]
+				boundary = transAnyState[1] == grBoundary
+			} else {
+				// No known transition. GB999: Any x Any.
+				g.state = grAny
+				boundary = true
+			}
+		}
+
+		// If we found a cluster boundary, let's stop here. The current cluster will
+		// be the one that just ended.
+		if g.pos-1 == 0 /* GB1 */ || boundary {
+			g.end = g.pos - 1
+			break
+		}
+	}
+
+	return g.start != g.end
+}
+
+// Runes returns a slice of runes (code points) which corresponds to the current
+// grapheme cluster. If the iterator is already past the end or Next() has not
+// yet been called, nil is returned.
+func (g *Graphemes) Runes() []rune {
+	if g.start == g.end {
+		return nil
+	}
+	return g.codePoints[g.start:g.end]
+}
+
+// Str returns a substring of the original string which corresponds to the
+// current grapheme cluster. If the iterator is already past the end or Next()
+// has not yet been called, an empty string is returned.
+func (g *Graphemes) Str() string {
+	if g.start == g.end {
+		return ""
+	}
+	return string(g.codePoints[g.start:g.end])
+}
+
+// Bytes returns a byte slice which corresponds to the current grapheme cluster.
+// If the iterator is already past the end or Next() has not yet been called,
+// nil is returned.
+func (g *Graphemes) Bytes() []byte {
+	if g.start == g.end {
+		return nil
+	}
+	return []byte(string(g.codePoints[g.start:g.end]))
+}
+
+// Positions returns the interval of the current grapheme cluster as byte
+// positions into the original string. The first returned value "from" indexes
+// the first byte and the second returned value "to" indexes the first byte that
+// is not included anymore, i.e. str[from:to] is the current grapheme cluster of
+// the original string "str". If Next() has not yet been called, both values are
+// 0. If the iterator is already past the end, both values are 1.
+func (g *Graphemes) Positions() (int, int) {
+	return g.indices[g.start], g.indices[g.end]
+}
+
+// Reset puts the iterator into its initial state such that the next call to
+// Next() sets it to the first grapheme cluster again.
+func (g *Graphemes) Reset() {
+	g.start, g.end, g.pos, g.state = 0, 0, 0, grAny
+	g.Next() // Parse ahead again.
+}
+
+// GraphemeClusterCount returns the number of user-perceived characters
+// (grapheme clusters) for the given string. To calculate this number, it
+// iterates through the string using the Graphemes iterator.
+func GraphemeClusterCount(s string) (n int) {
+	g := NewGraphemes(s)
+	for g.Next() {
+		n++
+	}
+	return
+}

vendor/modules.txt

@@ -107,7 +107,7 @@ github.com/jesseduffield/go-git/v5/utils/merkletrie/filesystem
 github.com/jesseduffield/go-git/v5/utils/merkletrie/index
 github.com/jesseduffield/go-git/v5/utils/merkletrie/internal/frame
 github.com/jesseduffield/go-git/v5/utils/merkletrie/noder
-# github.com/jesseduffield/gocui v0.3.1-0.20201010224802-8a6768078fd7
+# github.com/jesseduffield/gocui v0.3.1-0.20210208224444-2eecee85583d
 ## explicit
 github.com/jesseduffield/gocui
 # github.com/jesseduffield/termbox-go v0.0.0-20200823212418-a2289ed6aafe
@@ -133,7 +133,7 @@ github.com/kr/logfmt
 github.com/mattn/go-colorable
 # github.com/mattn/go-isatty v0.0.12
 github.com/mattn/go-isatty
-# github.com/mattn/go-runewidth v0.0.9
+# github.com/mattn/go-runewidth v0.0.10
 ## explicit
 github.com/mattn/go-runewidth
 # github.com/mgutz/str v1.2.0
@@ -141,12 +141,17 @@ github.com/mattn/go-runewidth
 github.com/mgutz/str
 # github.com/mitchellh/go-homedir v1.1.0
 github.com/mitchellh/go-homedir
+# github.com/nsf/termbox-go v0.0.0-20210114135735-d04385b850e8
+## explicit
 # github.com/onsi/ginkgo v1.10.3
 ## explicit
 # github.com/onsi/gomega v1.7.1
 ## explicit
 # github.com/pmezard/go-difflib v1.0.0
 github.com/pmezard/go-difflib/difflib
+# github.com/rivo/uniseg v0.2.0
+## explicit
+github.com/rivo/uniseg
 # github.com/sahilm/fuzzy v0.1.0
 ## explicit
 github.com/sahilm/fuzzy