fix(textarea): placeholder with chinese chars (#767)

go.mod

@@ -7,6 +7,7 @@ toolchain go1.23.7
 require (
 	github.com/MakeNowJust/heredoc v1.0.0
 	github.com/atotto/clipboard v0.1.4
+	github.com/aymanbagabas/go-udiff v0.2.0
 	github.com/charmbracelet/bubbletea v1.3.4
 	github.com/charmbracelet/harmonica v0.2.0
 	github.com/charmbracelet/lipgloss v1.1.0
@@ -22,7 +23,6 @@ require (
 
 require (
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
-	github.com/aymanbagabas/go-udiff v0.2.0 // indirect
 	github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc // indirect
 	github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd // indirect
 	github.com/charmbracelet/x/term v0.2.1 // indirect

textarea/textarea.go

@@ -1271,11 +1271,13 @@ func (m Model) placeholderView() string {
 		case i == 0:
 			// first character of first line as cursor with character
 			m.Cursor.TextStyle = m.style.computedPlaceholder()
-			m.Cursor.SetChar(string(plines[0][0]))
+
+			ch, rest, _, _ := uniseg.FirstGraphemeClusterInString(plines[0], 0)
+			m.Cursor.SetChar(ch)
 			s.WriteString(lineStyle.Render(m.Cursor.View()))
 
 			// the rest of the first line
-			s.WriteString(lineStyle.Render(style.Render(plines[0][1:] + strings.Repeat(" ", max(0, m.width-uniseg.StringWidth(plines[0]))))))
+			s.WriteString(lineStyle.Render(style.Render(rest)))
 		// remaining lines
 		case len(plines) > i:
 			// current line placeholder text

textarea/textarea_test.go

@@ -6,6 +6,7 @@ import (
 	"unicode"
 
 	"github.com/MakeNowJust/heredoc"
+	"github.com/aymanbagabas/go-udiff"
 	tea "github.com/charmbracelet/bubbletea"
 	"github.com/charmbracelet/lipgloss"
 	"github.com/charmbracelet/x/ansi"
@@ -1671,6 +1672,26 @@ func TestView(t *testing.T) {
 				`),
 			},
 		},
+		{
+			name: "placeholder chinese character",
+			modelFunc: func(m Model) Model {
+				m.Placeholder = "输入消息..."
+				m.ShowLineNumbers = true
+				m.SetWidth(20)
+				return m
+			},
+			want: want{
+				view: heredoc.Doc(`
+					>   1 输入消息...
+					>
+					>
+					>
+					>
+					>
+
+				`),
+			},
+		},
 	}
 
 	for _, tt := range tests {
@@ -1689,6 +1710,7 @@ func TestView(t *testing.T) {
 			wantView := stripString(tt.want.view)
 
 			if view != wantView {
+				t.Log(udiff.Unified("expected", "got", wantView, view))
 				t.Fatalf("Want:\n%v\nGot:\n%v\n", wantView, view)
 			}