perf: use uniseg.StringWidth

go.mod

@@ -2,4 +2,7 @@ module github.com/muesli/reflow
 
 go 1.13
 
-require github.com/mattn/go-runewidth v0.0.14
+require (
+	github.com/mattn/go-runewidth v0.0.14
+	github.com/rivo/uniseg v0.4.4
+)

go.sum

@@ -1,4 +1,5 @@
 github.com/mattn/go-runewidth v0.0.14 h1:+xnbZSEeDbOIg5/mE6JF0w6n9duR1l3/WmbinWVwUuU=
 github.com/mattn/go-runewidth v0.0.14/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
-github.com/rivo/uniseg v0.2.0 h1:S1pD9weZBuJdFmowNwbpi7BJ8TNftyUImj/0WQi72jY=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
+github.com/rivo/uniseg v0.4.4 h1:8TfxU8dW6PdqD27gjM8MVNuicgxIjxpm4K7x4jp8sis=
+github.com/rivo/uniseg v0.4.4/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=

padding/padding.go

@@ -5,8 +5,8 @@ import (
 	"io"
 	"strings"
 
-	"github.com/mattn/go-runewidth"
 	"github.com/muesli/reflow/ansi"
+	"github.com/rivo/uniseg"
 )
 
 type PaddingFunc func(w io.Writer)
@@ -71,7 +71,7 @@ func (w *Writer) Write(b []byte) (int, error) {
 				w.ansi = false
 			}
 		} else {
-			w.lineLen += runewidth.StringWidth(string(c))
+			w.lineLen += uniseg.StringWidth(string(c))
 
 			if c == '\n' {
 				// end of current line