Replaced runewidth.StringWidth() with my own implementation. Fixes #236

button.go

@@ -33,7 +33,7 @@ type Button struct {
 // NewButton returns a new input field.
 func NewButton(label string) *Button {
 	box := NewBox().SetBackgroundColor(Styles.ContrastBackgroundColor)
-	box.SetRect(0, 0, StringWidth(label)+4, 1)
+	box.SetRect(0, 0, TaggedStringWidth(label)+4, 1)
 	return &Button{
 		Box:                      box,
 		label:                    label,

dropdown.go

@@ -4,7 +4,6 @@ import (
 	"strings"
 
 	"github.com/gdamore/tcell"
-	runewidth "github.com/mattn/go-runewidth"
 )
 
 // dropDownOption is one option that can be selected in a drop-down primitive.
@@ -182,7 +181,7 @@ func (d *DropDown) GetFieldWidth() int {
 	}
 	fieldWidth := 0
 	for _, option := range d.options {
-		width := StringWidth(option.Text)
+		width := TaggedStringWidth(option.Text)
 		if width > fieldWidth {
 			fieldWidth = width
 		}
@@ -268,7 +267,7 @@ func (d *DropDown) Draw(screen tcell.Screen) {
 	// What's the longest option text?
 	maxWidth := 0
 	for _, option := range d.options {
-		strWidth := StringWidth(option.Text)
+		strWidth := TaggedStringWidth(option.Text)
 		if strWidth > maxWidth {
 			maxWidth = strWidth
 		}
@@ -294,7 +293,7 @@ func (d *DropDown) Draw(screen tcell.Screen) {
 	if d.open && len(d.prefix) > 0 {
 		// Show the prefix.
 		Print(screen, d.prefix, x, y, fieldWidth, AlignLeft, d.prefixTextColor)
-		prefixWidth := runewidth.StringWidth(d.prefix)
+		prefixWidth := stringWidth(d.prefix)
 		listItemText := d.options[d.list.GetCurrentItem()].Text
 		if prefixWidth < fieldWidth && len(d.prefix) < len(listItemText) {
 			Print(screen, listItemText[len(d.prefix):], x+prefixWidth, y, fieldWidth-prefixWidth, AlignLeft, d.fieldTextColor)

form.go

@@ -335,7 +335,7 @@ func (f *Form) Draw(screen tcell.Screen) {
 	// Find the longest label.
 	var maxLabelWidth int
 	for _, item := range f.items {
-		labelWidth := StringWidth(item.GetLabel())
+		labelWidth := TaggedStringWidth(item.GetLabel())
 		if labelWidth > maxLabelWidth {
 			maxLabelWidth = labelWidth
 		}
@@ -347,7 +347,7 @@ func (f *Form) Draw(screen tcell.Screen) {
 	var focusedPosition struct{ x, y, width, height int }
 	for index, item := range f.items {
 		// Calculate the space needed.
-		labelWidth := StringWidth(item.GetLabel())
+		labelWidth := TaggedStringWidth(item.GetLabel())
 		var itemWidth int
 		if f.horizontal {
 			fieldWidth := item.GetFieldWidth()
@@ -401,7 +401,7 @@ func (f *Form) Draw(screen tcell.Screen) {
 	buttonWidths := make([]int, len(f.buttons))
 	buttonsWidth := 0
 	for index, button := range f.buttons {
-		w := StringWidth(button.GetLabel()) + 4
+		w := TaggedStringWidth(button.GetLabel()) + 4
 		buttonWidths[index] = w
 		buttonsWidth += w + 1
 	}

inputfield.go

@@ -7,7 +7,6 @@ import (
 	"unicode/utf8"
 
 	"github.com/gdamore/tcell"
-	runewidth "github.com/mattn/go-runewidth"
 )
 
 // InputField is a one-line box (three lines if there is a title) where the
@@ -276,8 +275,7 @@ func (i *InputField) Draw(screen tcell.Screen) {
 		if i.maskCharacter > 0 {
 			text = strings.Repeat(string(i.maskCharacter), utf8.RuneCountInString(i.text))
 		}
-		stringWidth := runewidth.StringWidth(text)
+		if fieldWidth >= stringWidth(text) {
-		if fieldWidth >= stringWidth {
 			// We have enough space for the full text.
 			Print(screen, Escape(text), x, y, fieldWidth, AlignLeft, i.fieldTextColor)
 			i.offset = 0
@@ -299,7 +297,7 @@ func (i *InputField) Draw(screen tcell.Screen) {
 			var shiftLeft int
 			if i.offset > i.cursorPos {
 				i.offset = i.cursorPos
-			} else if subWidth := runewidth.StringWidth(text[i.offset:i.cursorPos]); subWidth > fieldWidth-1 {
+			} else if subWidth := stringWidth(text[i.offset:i.cursorPos]); subWidth > fieldWidth-1 {
 				shiftLeft = subWidth - fieldWidth + 1
 			}
 			currentOffset := i.offset

list.go

@@ -426,7 +426,7 @@ func (l *List) Draw(screen tcell.Screen) {
 		if index == l.currentItem && (!l.selectedFocusOnly || l.HasFocus()) {
 			textWidth := width
 			if !l.highlightFullLine {
-				if w := StringWidth(item.MainText); w < textWidth {
+				if w := TaggedStringWidth(item.MainText); w < textWidth {
 					textWidth = w
 				}
 			}

modal.go

@@ -116,7 +116,7 @@ func (m *Modal) Draw(screen tcell.Screen) {
 	// Calculate the width of this modal.
 	buttonsWidth := 0
 	for _, button := range m.form.buttons {
-		buttonsWidth += StringWidth(button.label) + 4 + 2
+		buttonsWidth += TaggedStringWidth(button.label) + 4 + 2
 	}
 	buttonsWidth -= 2
 	screenWidth, screenHeight := screen.Size()

table.go

@@ -792,7 +792,7 @@ ColumnLoop:
 			}
 			cell.x, cell.y, cell.width = x+columnX+1, y+rowY, finalWidth
 			_, printed := printWithStyle(screen, cell.Text, x+columnX+1, y+rowY, finalWidth, cell.Align, tcell.StyleDefault.Foreground(cell.Color)|tcell.Style(cell.Attributes))
-			if StringWidth(cell.Text)-printed > 0 && printed > 0 {
+			if TaggedStringWidth(cell.Text)-printed > 0 && printed > 0 {
 				_, _, style, _ := screen.GetContent(x+columnX+1+finalWidth-1, y+rowY)
 				printWithStyle(screen, string(SemigraphicsHorizontalEllipsis), x+columnX+1+finalWidth-1, y+rowY, 1, AlignLeft, style)
 			}

textview.go

@@ -691,7 +691,7 @@ func (t *TextView) reindexBuffer(width int) {
 						line := len(t.index)
 						if t.fromHighlight < 0 {
 							t.fromHighlight, t.toHighlight = line, line
-							t.posHighlight = runewidth.StringWidth(splitLine[:strippedTagStart])
+							t.posHighlight = stringWidth(splitLine[:strippedTagStart])
 						} else if line > t.toHighlight {
 							t.toHighlight = line
 						}
@@ -709,7 +709,7 @@ func (t *TextView) reindexBuffer(width int) {
 
 			// Append this line.
 			line.NextPos = originalPos
-			line.Width = runewidth.StringWidth(splitLine)
+			line.Width = stringWidth(splitLine)
 			t.index = append(t.index, line)
 		}
 
@@ -721,7 +721,7 @@ func (t *TextView) reindexBuffer(width int) {
 				if spaces != nil && spaces[len(spaces)-1][1] == len(str) {
 					oldNextPos := line.NextPos
 					line.NextPos -= spaces[len(spaces)-1][1] - spaces[len(spaces)-1][0]
-					line.Width -= runewidth.StringWidth(t.buffer[line.Line][line.NextPos:oldNextPos])
+					line.Width -= stringWidth(t.buffer[line.Line][line.NextPos:oldNextPos])
 				}
 			}
 		}

util.go

@@ -171,7 +171,7 @@ func overlayStyle(background tcell.Color, defaultStyle tcell.Style, fgColor, bgC
 func decomposeString(text string, findColors, findRegions bool) (colorIndices [][]int, colors [][]string, regionIndices [][]int, regions [][]string, escapeIndices [][]int, stripped string, width int) {
 	// Shortcut for the trivial case.
 	if !findColors && !findRegions {
-		return nil, nil, nil, nil, nil, text, runewidth.StringWidth(text)
+		return nil, nil, nil, nil, nil, text, stringWidth(text)
 	}
 
 	// Get positions of any tags.
@@ -222,7 +222,7 @@ func decomposeString(text string, findColors, findRegions bool) (colorIndices []
 	stripped = string(escapePattern.ReplaceAll(buf, []byte("[$1$2]")))
 
 	// Get the width of the stripped string.
-	width = runewidth.StringWidth(stripped)
+	width = stringWidth(stripped)
 
 	return
 }
@@ -409,13 +409,31 @@ func PrintSimple(screen tcell.Screen, text string, x, y int) {
 	Print(screen, text, x, y, math.MaxInt32, AlignLeft, Styles.PrimaryTextColor)
 }
 
-// StringWidth returns the width of the given string needed to print it on
+// TaggedStringWidth returns the width of the given string needed to print it on
 // screen. The text may contain color tags which are not counted.
-func StringWidth(text string) int {
+func TaggedStringWidth(text string) int {
 	_, _, _, _, _, _, width := decomposeString(text, true, false)
 	return width
 }
 
+// stringWidth returns the number of horizontal cells needed to print the given
+// text. It splits the text into its grapheme clusters, calculates each
+// cluster's width, and adds them up to a total.
+func stringWidth(text string) (width int) {
+	g := uniseg.NewGraphemes(text)
+	for g.Next() {
+		var chWidth int
+		for _, r := range g.Runes() {
+			chWidth = runewidth.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
+}
+
 // WordWrap splits a text such that each resulting line does not exceed the
 // given screen width. Possible split points are after any punctuation or
 // whitespace. Whitespace after split points will be dropped.
@@ -534,7 +552,7 @@ func iterateString(text string, callback func(main rune, comb []rune, textPos, t
 	for gr.Next() {
 		r := gr.Runes()
 		from, to := gr.Positions()
-		width := runewidth.StringWidth(gr.Str())
+		width := stringWidth(gr.Str())
 		var comb []rune
 		if len(r) > 1 {
 			comb = r[1:]