Handle wide characters in the renderer

3 files changed, 18 insertions, 13 deletions

diff --git a/go.mod b/go.mod
index d3d80df..9b7c1fe 100644
--- a/go.mod
+++ b/go.mod
@@ -4,8 +4,8 @@ go 1.24.1
 
 require (
 	github.com/charmbracelet/bubbles v0.21.0
-	github.com/charmbracelet/bubbletea v1.3.4
 	github.com/charmbracelet/lipgloss v1.1.0
+	github.com/mattn/go-runewidth v0.0.16
 	github.com/pkg/sftp v1.13.9
 	github.com/rhogenson/deque v1.1.0
 	golang.org/x/crypto v0.37.0
@@ -14,6 +14,7 @@ require (
 
 require (
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
+	github.com/charmbracelet/bubbletea v1.3.4 // indirect
 	github.com/charmbracelet/colorprofile v0.3.0 // indirect
 	github.com/charmbracelet/harmonica v0.2.0 // indirect
 	github.com/charmbracelet/x/ansi v0.8.0 // indirect
@@ -24,7 +25,6 @@ require (
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/mattn/go-localereader v0.0.1 // indirect
-	github.com/mattn/go-runewidth v0.0.16 // indirect
 	github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6 // indirect
 	github.com/muesli/cancelreader v0.2.2 // indirect
 	github.com/muesli/termenv v0.16.0 // indirect
diff --git a/go.sum b/go.sum
index c7aa66b..02879df 100644
--- a/go.sum
+++ b/go.sum
@@ -42,8 +42,6 @@ github.com/pkg/sftp v1.13.9 h1:4NGkvGudBL7GteO3m6qnaQ4pC0Kvf0onSVc9gR3EWBw=
 github.com/pkg/sftp v1.13.9/go.mod h1:OBN7bVXdstkFFN/gdnHPUb5TE8eb8G1Rp9wCItqjkkA=
 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/rhogenson/deque v1.0.1 h1:YWzJiImHBaITBHjQ6eXzc6v1oCTvk9r9vrHqjxB4aOk=
-github.com/rhogenson/deque v1.0.1/go.mod h1:3JVW0+HcBcOClQtYlHhsyE5Q5cr/qG1jLEeC46prdtQ=
 github.com/rhogenson/deque v1.1.0 h1:3poepkqJjq3jp+s3eqQ/WTAtiX1hXOmpp+h8l2+PwFI=
 github.com/rhogenson/deque v1.1.0/go.mod h1:3JVW0+HcBcOClQtYlHhsyE5Q5cr/qG1jLEeC46prdtQ=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
diff --git a/internal/render/render.go b/internal/render/render.go
index 18708f3..c43d2e8 100644
--- a/internal/render/render.go
+++ b/internal/render/render.go
@@ -6,7 +6,8 @@ import (
 	"bytes"
 	"fmt"
 	"os"
-	"unicode/utf8"
+
+	runewidth "github.com/mattn/go-runewidth"
 )
 
 // Renderer updates a terminal UI. Typical usage looks like
@@ -46,9 +47,13 @@ func (r *Renderer) Clear(width int) {
 }
 
 func truncate(b []byte, width int) ([]byte, int) {
-	n := 0
+	str := string(b)
+	currentWidth := 0
 	for i := 0; i < len(b); {
-		if bytes.HasPrefix(b[i:], []byte("\033[")) {
+		chunkBytes := bytes.Index(b[i:], []byte("\033["))
+		if chunkBytes < 0 {
+			chunkBytes = len(b) - i
+		} else if chunkBytes == 0 {
 			// An escape sequence usually starts with [, then has one or two numbers
 			// separated by semicolon, and ends with some terminating character. To
 			// try and munch the whole sequence, skip over any numbers and
@@ -59,14 +64,16 @@ func truncate(b []byte, width int) ([]byte, int) {
 			i++
 			continue
 		}
-		if n+1 > width {
-			return b[:i], n
+		chunkWidth := runewidth.StringWidth(str[i : i+chunkBytes])
+		if currentWidth+chunkWidth <= width {
+			i += chunkBytes
+			currentWidth += chunkWidth
+			continue
 		}
-		_, runeWidth := utf8.DecodeRune(b[i:])
-		i += runeWidth
-		n++
+		lastChunk := runewidth.Truncate(str[i:i+chunkBytes], width-currentWidth, "")
+		return b[:i+len(lastChunk)], width
 	}
-	return b, n
+	return b, currentWidth
 }
 
 // Write implements io.Writer.