feat(textarea) Add multiline placeholder

Add the capability to show a multiline placeholder. Some refactoring was
required to improve readability and improve logic.

End of line buffer character was only shown when line numbers were
displayed which requires some verification whether this is the intended
outcome. This change resolves this issue.

textarea/textarea.go

@@ -1140,36 +1140,48 @@ func (m Model) getPromptString(displayLine int) (prompt string) {
 func (m Model) placeholderView() string {
 	var (
 		s     strings.Builder
-		p     = rw.Truncate(m.Placeholder, m.width, "...")
+		p     = m.Placeholder
 		style = m.style.Placeholder.Inline(true)
 	)
 
-	prompt := m.getPromptString(0)
-	prompt = m.style.Prompt.Render(prompt)
-	s.WriteString(m.style.CursorLine.Render(prompt))
+	// split string by new lines
+	plines := strings.Split(strings.TrimSpace(p), "\n")
 
-	if m.ShowLineNumbers {
-		s.WriteString(m.style.CursorLine.Render(m.style.CursorLineNumber.Render((fmt.Sprintf(m.lineNumberFormat, 1)))))
-	}
-
-	m.Cursor.TextStyle = m.style.Placeholder
-	m.Cursor.SetChar(string(p[0]))
-	s.WriteString(m.style.CursorLine.Render(m.Cursor.View()))
-
-	// The rest of the placeholder text
-	s.WriteString(m.style.CursorLine.Render(style.Render(p[1:] + strings.Repeat(" ", max(0, m.width-rw.StringWidth(p))))))
-
-	// The rest of the new lines
-	for i := 1; i < m.height; i++ {
-		s.WriteRune('\n')
+	for i := 0; i < m.height; i++ {
+		// render prompt
 		prompt := m.getPromptString(i)
 		prompt = m.style.Prompt.Render(prompt)
-		s.WriteString(prompt)
+		s.WriteString(m.style.CursorLine.Render(prompt))
 
+		// render line numbers
 		if m.ShowLineNumbers {
-			eob := m.style.EndOfBuffer.Render((fmt.Sprintf(m.lineNumberFormat, string(m.EndOfBufferCharacter))))
+			s.WriteString(m.style.CursorLine.Render(m.style.CursorLineNumber.Render((fmt.Sprintf(m.lineNumberFormat, i+1)))))
+		}
+
+		switch {
+		// first line
+		case i == 0:
+			// first character of first line as cursor with character
+			m.Cursor.TextStyle = m.style.Placeholder
+			m.Cursor.SetChar(string(plines[0][0]))
+			s.WriteString(m.style.CursorLine.Render(m.Cursor.View()))
+
+			// the rest of the first line
+			s.WriteString(m.style.CursorLine.Render(style.Render(plines[0][1:] + strings.Repeat(" ", max(0, m.width-rw.StringWidth(plines[0]))))))
+		// remaining lines
+		case len(plines) > i:
+			// current line placeholder text
+			if len(plines) > i {
+				s.WriteString(m.style.CursorLine.Render(style.Render(plines[i] + strings.Repeat(" ", max(0, m.width-rw.StringWidth(plines[i]))))))
+			}
+		default:
+			// end of line buffer character
+			eob := m.style.EndOfBuffer.Render(string(m.EndOfBufferCharacter))
 			s.WriteString(eob)
 		}
+
+		// terminate with new line
+		s.WriteRune('\n')
 	}
 
 	m.viewport.SetContent(s.String())

textarea/textarea_test.go

@@ -428,6 +428,29 @@ func TestRendersEndOfLineBuffer(t *testing.T) {
 	}
 }
 
+func TestRendersMultilinePlaceholder(t *testing.T) {
+	lines := []string{
+		"the first line",
+		"the second line",
+		"the third line",
+	}
+
+	textarea := newTextArea()
+	textarea.Placeholder = strings.Join(lines, "\n")
+	view := textarea.View()
+
+	for i, line := range strings.Split(view, "\n") {
+		if i == len(lines) {
+			break
+		}
+
+		if !strings.Contains(line, lines[i][1:]) {
+			t.Log(view)
+			t.Error("Expected to see line in placeholder")
+		}
+	}
+}
+
 func newTextArea() Model {
 	textarea := New()