Merge pull request #1 from charmbracelet/feature/i236-viewport-horizontal-scroll

Feature/i236 viewport horizontal scroll

viewport/viewport.go

@@ -62,9 +62,10 @@ type Model struct {
 	// horizontal step represents the step of indent we add with one move left or right.
 	horizontalStep int
 
-	indent      int
-	initialized bool
-	lines       []string
+	indent           int
+	initialized      bool
+	lines            []string
+	longestLineWidth int
 }
 
 func (m *Model) setInitialValues() {
@@ -113,6 +114,7 @@ func (m Model) ScrollPercent() float64 {
 func (m *Model) SetContent(s string) {
 	s = strings.ReplaceAll(s, "\r\n", "\n") // normalize line endings
 	m.lines = strings.Split(s, "\n")
+	m.longestLineWidth = findLongestLineWidth(m.lines)
 
 	if m.YOffset > len(m.lines)-1 {
 		m.GotoBottom()
@@ -331,6 +333,10 @@ func (m *Model) MoveLeft() {
 
 // MoveRight moves all lines to set runes right.
 func (m *Model) MoveRight() {
+	// prevents over scrolling to the right
+	if m.indent >= m.longestLineWidth-m.Width {
+		return
+	}
 	m.indent += m.horizontalStep
 }
 
@@ -473,3 +479,13 @@ func max(a, b int) int {
 	}
 	return b
 }
+
+func findLongestLineWidth(lines []string) int {
+	w := 0
+	for _, l := range lines {
+		if ww := ansi.StringWidth(l); ww > w {
+			w = ww
+		}
+	}
+	return w
+}