feat: New Border Title API

README.md

@@ -203,6 +203,37 @@ lipgloss.NewStyle().
 lipgloss.NewStyle().
     Border(lipgloss.DoubleBorder(), true, false, false, true)
 ```
+It is also possible to set and style a border title
+```go
+
+   // create bold italic title horizontally aligned 
+   // to center of the border 
+   titleStyle := lipgloss.NewStyle().
+        Background(lipgloss.Color("#6124DF")).
+        Align(lipgloss.Center).
+        Bold(true).
+        Italic(true)
+
+   // dialog box style with its title styled
+   dialogBoxStyle := lipgloss.NewStyle().
+        Border(lipgloss.RoundedBorder()).
+        BorderForeground(lipgloss.Color("#874BFD")).
+	    BorderTitleStyle(titleStyle).
+        Padding(1, 0).
+        BorderTop(true).
+        BorderLeft(true).
+        BorderRight(true).
+        BorderBottom(true)
+
+
+    // Use the title with the dialog box style
+    dialog := lipgloss.Place(width, 9,
+        lipgloss.Center, lipgloss.Center,
+        dialogBoxStyle.Copy().BorderTitle(" Question ").Render(ui),
+        lipgloss.WithWhitespaceChars("猫咪"),
+        lipgloss.WithWhitespaceForeground(subtle),
+    )
+```
 
 For more on borders see [the docs][docs].
 

borders.go

@@ -246,11 +246,39 @@ func (s Style) applyBorder(str string) string {
 	border.BottomLeft = getFirstRuneAsString(border.BottomLeft)
 
 	var out strings.Builder
+	const sideCount = 2
 
 	// Render top
 	if hasTop {
-		top := renderHorizontalEdge(border.TopLeft, border.Top, border.TopRight, width)
-		top = styleBorder(top, topFG, topBG)
+		top := ""
+
+		// sanitize title style
+		titleStyle := s.GetBorderTitleStyle().Copy().Inline(true).MaxWidth(width)
+		title := s.GetBorderTitle()
+
+		if len(strings.TrimSpace(title)) > 0 {
+			titleLen := len(title)
+			topBeforeTitle := border.TopLeft
+			topAfterTitle := border.TopRight
+			switch titleStyle.GetAlignHorizontal() {
+			case Right:
+				topBeforeTitle = border.TopLeft + repeatStr(border.Top, width-1-titleLen)
+			case Center:
+				noTitleLen := width - 1 - titleLen
+				noTitleLen2 := noTitleLen / sideCount
+				topBeforeTitle = border.TopLeft + repeatStr(border.Top, noTitleLen2)
+				topAfterTitle = repeatStr(border.Top, noTitleLen-noTitleLen2) + border.TopRight
+			case Left:
+				topAfterTitle = repeatStr(border.Top, width-1-titleLen) + border.TopRight
+			}
+
+			top = styleBorder(topBeforeTitle, topFG, topBG) +
+				titleStyle.Render(title) +
+				styleBorder(topAfterTitle, topFG, topBG)
+		} else {
+			top = renderHorizontalEdge(border.TopLeft, border.Top, border.TopRight, width)
+			top = styleBorder(top, topFG, topBG)
+		}
 		out.WriteString(top)
 		out.WriteRune('\n')
 	}
@@ -296,6 +324,13 @@ func (s Style) applyBorder(str string) string {
 	return out.String()
 }
 
+func repeatStr(s string, count int) string {
+	if count <= 0 {
+		return ""
+	}
+	return strings.Repeat(s, count)
+}
+
 // Render the horizontal (top or bottom) portion of a border.
 func renderHorizontalEdge(left, middle, right string, width int) string {
 	if width < 1 {
@@ -314,6 +349,7 @@ func renderHorizontalEdge(left, middle, right string, width int) string {
 
 	out := strings.Builder{}
 	out.WriteString(left)
+
 	for i := leftWidth + rightWidth; i < width+rightWidth; {
 		out.WriteRune(runes[j])
 		j++

example/main.go

@@ -92,9 +92,16 @@ var (
 
 	// Dialog.
 
+	dialogTitleStyle = lipgloss.NewStyle().
+				Background(lipgloss.Color("#6124DF")).
+				Align(lipgloss.Center).
+				Bold(true).
+				Italic(true)
+
 	dialogBoxStyle = lipgloss.NewStyle().
 			Border(lipgloss.RoundedBorder()).
 			BorderForeground(lipgloss.Color("#874BFD")).
+			BorderTitleStyle(dialogTitleStyle).
 			Padding(1, 0).
 			BorderTop(true).
 			BorderLeft(true).
@@ -239,7 +246,7 @@ func main() {
 
 		dialog := lipgloss.Place(width, 9,
 			lipgloss.Center, lipgloss.Center,
-			dialogBoxStyle.Render(ui),
+			dialogBoxStyle.Copy().BorderTitle(" Question ").Render(ui),
 			lipgloss.WithWhitespaceChars("猫咪"),
 			lipgloss.WithWhitespaceForeground(subtle),
 		)

get.go

@@ -434,6 +434,24 @@ func (s Style) getAsInt(k propKey) int {
 	return 0
 }
 
+func (s Style) getAsString(k propKey) string {
+	if v, ok := s.rules[k]; ok {
+		if s, ok := v.(string); ok {
+			return s
+		}
+	}
+	return ""
+}
+
+func (s Style) getAsStyle(k propKey) Style {
+	if v, ok := s.rules[k]; ok {
+		if s, ok := v.(Style); ok {
+			return s
+		}
+	}
+	return NewStyle()
+}
+
 func (s Style) getAsPosition(k propKey) Position {
 	v, ok := s.rules[k]
 	if !ok {
@@ -456,7 +474,19 @@ func (s Style) getBorderStyle() Border {
 	return noBorder
 }
 
-// Split a string into lines, additionally returning the size of the widest
+// GetBorderTitleStyle returns border title style if set,
+// otherwise returns empty style.
+func (s Style) GetBorderTitleStyle() Style {
+	return s.getAsStyle(borderTitleStyleKey)
+}
+
+// GetBorderTitle returns border title if set,
+// otherwise returns empty string.
+func (s Style) GetBorderTitle() string {
+	return s.getAsString(borderTitleKey)
+}
+
+// Split a string into lines, additionally returning the size of the widest.
 // line.
 func getLines(s string) (lines []string, widest int) {
 	lines = strings.Split(s, "\n")

set.go

@@ -454,6 +454,18 @@ func (s Style) BorderLeftBackground(c TerminalColor) Style {
 	return s
 }
 
+// BorderTitleStyle set border title style
+func (s Style) BorderTitleStyle(style Style) Style {
+	s.set(borderTitleStyleKey, style)
+	return s
+}
+
+// BorderTitle set border title
+func (s Style) BorderTitle(title string) Style {
+	s.set(borderTitleKey, title)
+	return s
+}
+
 // Inline makes rendering output one line and disables the rendering of
 // margins, padding and borders. This is useful when you need a style to apply
 // only to font rendering and don't want it to change any physical dimensions.

style.go

@@ -65,6 +65,10 @@ const (
 	borderBottomBackgroundKey
 	borderLeftBackgroundKey
 
+	// Border title.
+	borderTitleStyleKey
+	borderTitleKey
+
 	inlineKey
 	maxWidthKey
 	maxHeightKey