Improve performance of maxRuneWidth (#592)

Author: clipperhouse

borders.go

@@ -5,8 +5,8 @@ import (
 	"unicode/utf8"
 
 	"github.com/charmbracelet/x/ansi"
+	"github.com/clipperhouse/displaywidth"
 	"github.com/muesli/termenv"
-	"github.com/rivo/uniseg"
 )
 
 // Border contains a series of values which comprise the various parts of a
@@ -57,10 +57,7 @@ func (b Border) GetLeftSize() int {
 
 func getBorderEdgeWidth(borderParts ...string) (maxWidth int) {
 	for _, piece := range borderParts {
-		w := maxRuneWidth(piece)
-		if w > maxWidth {
-			maxWidth = w
-		}
+		maxWidth = max(maxWidth, maxRuneWidth(piece))
 	}
 	return maxWidth
 }
@@ -468,17 +465,19 @@ func (s Style) styleBorder(border string, fg, bg TerminalColor) string {
 }
 
 func maxRuneWidth(str string) int {
+	switch len(str) {
+	case 0:
+		return 0
+	case 1:
+		return displaywidth.String(str)
+	}
+
 	var width int
 
-	state := -1
-	for len(str) > 0 {
-		var w int
-		_, str, w, state = uniseg.FirstGraphemeClusterInString(str, state)
-		if w > width {
-			width = w
-		}
+	g := displaywidth.StringGraphemes(str)
+	for g.Next() {
+		width = max(width, g.Width())
 	}
-
 	return width
 }
 

borders_test.go

@@ -2,6 +2,8 @@ package lipgloss
 
 import (
 	"testing"
+
+	"github.com/rivo/uniseg"
 )
 
 func TestStyle_GetBorderSizes(t *testing.T) {
@@ -173,3 +175,49 @@ func BenchmarkGetFirstRuneAsString(b *testing.B) {
 		}
 	})
 }
+
+func BenchmarkMaxRuneWidth(b *testing.B) {
+	testCases := []struct {
+		name string
+		str  string
+	}{
+		{"Blank", " "},
+		{"ASCII", "+"},
+		{"Markdown", "|"},
+		{"Normal", "├"},
+		{"Rounded", "╭"},
+		{"Block", "█"},
+		{"Emoji", "😀"},
+	}
+	for _, tc := range testCases {
+		b.Run(tc.name, func(b *testing.B) {
+			b.Run("Before", func(b *testing.B) {
+				b.ReportAllocs()
+				for b.Loop() {
+					_ = maxRuneWidthOld(tc.str)
+				}
+			})
+			b.Run("After", func(b *testing.B) {
+				b.ReportAllocs()
+				for b.Loop() {
+					_ = maxRuneWidth(tc.str)
+				}
+			})
+		})
+	}
+}
+
+func maxRuneWidthOld(str string) int {
+	var width int
+
+	state := -1
+	for len(str) > 0 {
+		var w int
+		_, str, w, state = uniseg.FirstGraphemeClusterInString(str, state)
+		if w > width {
+			width = w
+		}
+	}
+
+	return width
+}

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/charmbracelet/x/ansi v0.10.2
 	github.com/charmbracelet/x/cellbuf v0.0.13
 	github.com/charmbracelet/x/exp/golden v0.0.0-20250609102027-b60490452b30
+	github.com/clipperhouse/displaywidth v0.6.2
 	github.com/muesli/termenv v0.16.0
 	github.com/rivo/uniseg v0.4.7
 )
@@ -19,6 +20,8 @@ require (
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
 	github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc // indirect
 	github.com/charmbracelet/x/term v0.2.1 // indirect
+	github.com/clipperhouse/stringish v0.1.1 // indirect
+	github.com/clipperhouse/uax29/v2 v2.3.0 // indirect
 	github.com/lucasb-eyer/go-colorful v1.3.0 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/mattn/go-runewidth v0.0.17 // indirect

go.sum

@@ -12,6 +12,12 @@ github.com/charmbracelet/x/exp/golden v0.0.0-20250609102027-b60490452b30 h1:lF42
 github.com/charmbracelet/x/exp/golden v0.0.0-20250609102027-b60490452b30/go.mod h1:IfZAMTHB6XkZSeXUqriemErjAWCCzT0LwjKFYCZyw0I=
 github.com/charmbracelet/x/term v0.2.1 h1:AQeHeLZ1OqSXhrAWpYUtZyX1T3zVxfpZuEQMIQaGIAQ=
 github.com/charmbracelet/x/term v0.2.1/go.mod h1:oQ4enTYFV7QN4m0i9mzHrViD7TQKvNEEkHUMCmsxdUg=
+github.com/clipperhouse/displaywidth v0.6.2 h1:ZDpTkFfpHOKte4RG5O/BOyf3ysnvFswpyYrV7z2uAKo=
+github.com/clipperhouse/displaywidth v0.6.2/go.mod h1:R+kHuzaYWFkTm7xoMmK1lFydbci4X2CicfbGstSGg0o=
+github.com/clipperhouse/stringish v0.1.1 h1:+NSqMOr3GR6k1FdRhhnXrLfztGzuG+VuFDfatpWHKCs=
+github.com/clipperhouse/stringish v0.1.1/go.mod h1:v/WhFtE1q0ovMta2+m+UbpZ+2/HEXNWYXQgCt4hdOzA=
+github.com/clipperhouse/uax29/v2 v2.3.0 h1:SNdx9DVUqMoBuBoW3iLOj4FQv3dN5mDtuqwuhIGpJy4=
+github.com/clipperhouse/uax29/v2 v2.3.0/go.mod h1:Wn1g7MK6OoeDT0vL+Q0SQLDz/KpfsVRgg6W7ihQeh4g=
 github.com/lucasb-eyer/go-colorful v1.3.0 h1:2/yBRLdWBZKrf7gB40FoiKfAWYQ0lqNcbuQwVHXptag=
 github.com/lucasb-eyer/go-colorful v1.3.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
 github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=