Integrate viewport navigation controls with new renderer

viewport/renderer.go

@@ -30,37 +30,37 @@ func (r *renderer) clear() {
 func (r *renderer) sync(lines []string) {
 	r.clear()
 	moveTo(r.Out, r.Y, 0)
-	r.write(lines)
+	r.writeLines(lines)
 }
 
 // write writes to the set writer.
-func (r *renderer) write(lines []string) {
+func (r *renderer) writeLines(lines []string) {
 	if len(lines) == 0 {
 		return
 	}
 	io.WriteString(r.Out, strings.Join(lines, "\r\n"))
 }
 
-// Effectively scroll up. That is, insert a line at the top, scrolling
+// Effectively scroll up. That is, insert a line at the top, pushing
 // everything else down. This is roughly how ncurses does it.
-func (r *renderer) insertTop(line string) {
+func (r *renderer) insertTop(lines []string) {
 	changeScrollingRegion(r.Out, r.Y, r.Y+r.Height)
 	moveTo(r.Out, r.Y, 0)
-	insertLine(r.Out, 1)
-	io.WriteString(r.Out, line)
+	insertLine(r.Out, len(lines))
+	r.writeLines(lines)
 	changeScrollingRegion(r.Out, r.TerminalWidth, r.TerminalHeight)
 }
 
-// Effectively scroll down. That is, insert a line at the bottom, scrolling
+// Effectively scroll down. That is, insert a line at the bottom, pushing
 // everything else up. This is roughly how ncurses does it.
-func (r *renderer) insertBottom(line string) {
+func (r *renderer) insertBottom(lines []string) {
 	changeScrollingRegion(r.Out, r.Y, r.Y+r.Height)
 	moveTo(r.Out, r.Y+r.Height, 0)
-	io.WriteString(r.Out, "\n"+line)
+	io.WriteString(r.Out, "\r\n"+strings.Join(lines, "\r\n"))
 	changeScrollingRegion(r.Out, r.TerminalWidth, r.TerminalHeight)
 }
 
-// Screen command
+// Terminal Control
 
 const csi = "\x1b["
 

viewport/viewport.go

@@ -45,6 +45,16 @@ func NewModel(yPos, width, height, terminalWidth, terminalHeight int) Model {
 	}
 }
 
+// AtTop returns whether or not the viewport is in the very top position.
+func (m Model) AtTop() bool {
+	return m.YOffset <= 0
+}
+
+// AtBottom returns whether or not the viewport is at the very botom position.
+func (m Model) AtBottom() bool {
+	return m.YOffset >= len(m.lines)-m.Height-1
+}
+
 // Scrollpercent returns the amount scrolled as a float between 0 and 1.
 func (m Model) ScrollPercent() float64 {
 	if m.Height >= len(m.lines) {
@@ -61,53 +71,117 @@ func (m *Model) SetContent(s string) {
 	s = strings.Replace(s, "\r\n", "\n", -1) // normalize line endings
 	m.lines = strings.Split(s, "\n")
 
-	lines := bounded(m.lines, m.YOffset, m.Height)
-	m.r.sync(lines)
+	if m.UseInternalRenderer {
+		top := max(m.YOffset, 0)
+		bottom := min(m.YOffset+m.Height, len(m.lines))
+		m.r.sync(m.lines[top:bottom])
+	}
 }
 
 // ViewDown moves the view down by the number of lines in the viewport.
 // Basically, "page down".
 func (m *Model) ViewDown() {
-	m.YOffset = min(len(m.lines)-m.Height, m.YOffset+m.Height)
+	if m.AtBottom() {
+		return
+	}
+
+	if m.UseInternalRenderer {
+		top := max(m.YOffset+m.Height, 0)
+		bottom := min(top+m.Height, len(m.lines)-1)
+		m.r.insertBottom(m.lines[top:bottom])
+	}
+
+	m.YOffset = min(
+		m.YOffset+m.Height,    // target
+		len(m.lines)-m.Height, // fallback
+	)
 }
 
 // ViewUp moves the view up by one height of the viewport. Basically, "page up".
 func (m *Model) ViewUp() {
-	m.YOffset = max(0, m.YOffset-m.Height)
-}
+	if m.AtTop() {
+		return
+	}
 
-// HalfViewUp moves the view up by half the height of the viewport.
-func (m *Model) HalfViewUp() {
-	m.YOffset = max(0, m.YOffset-m.Height/2)
+	if m.UseInternalRenderer {
+		top := max(m.YOffset-m.Height, 0)
+		bottom := min(m.YOffset, len(m.lines))
+		m.r.insertTop(m.lines[top:bottom])
+	}
+
+	m.YOffset = max(
+		m.YOffset-m.Height, // target
+		0,                  // fallback
+	)
 }
 
 // HalfViewDown moves the view down by half the height of the viewport.
 func (m *Model) HalfViewDown() {
-	m.YOffset = min(len(m.lines)-m.Height, m.YOffset+m.Height/2)
+	if m.AtBottom() {
+		return
+	}
+
+	if m.UseInternalRenderer {
+		top := max(m.YOffset+m.Height/2, 0)
+		bottom := min(top+m.Height, len(m.lines)-1)
+		m.r.insertBottom(m.lines[top:bottom])
+	}
+
+	m.YOffset = min(
+		m.YOffset+m.Height/2,  // target
+		len(m.lines)-m.Height, // fallback
+	)
+}
+
+// HalfViewUp moves the view up by half the height of the viewport.
+func (m *Model) HalfViewUp() {
+	if m.AtTop() {
+		return
+	}
+
+	if m.UseInternalRenderer {
+		top := max(m.YOffset-m.Height/2, 0)
+		bottom := clamp(m.YOffset, top, len(m.lines))
+		m.r.insertTop(m.lines[top:bottom])
+	}
+
+	m.YOffset = max(
+		m.YOffset-m.Height/2, // target
+		0,                    // fallback
+	)
 }
 
 // LineDown moves the view up by the given number of lines.
 func (m *Model) LineDown(n int) {
-	if m.YOffset >= len(m.lines)-m.Height-1 {
+	if m.AtBottom() || n == 0 {
 		return
 	}
-	m.YOffset = min(len(m.lines)-m.Height, m.YOffset+n)
 
 	if m.UseInternalRenderer {
-		m.r.insertBottom(m.lines[m.YOffset+m.Height-1])
+		bottom := min(m.YOffset+m.Height+n, len(m.lines))
+		top := max(bottom-n, 0)
+		m.r.insertBottom(m.lines[top:bottom])
 	}
+
+	m.YOffset = min(
+		m.YOffset+n,           // target
+		len(m.lines)-m.Height, // fallback
+	)
 }
 
 // LineUp moves the view down by the given number of lines.
 func (m *Model) LineUp(n int) {
-	if m.YOffset == 0 {
+	if m.AtTop() || n == 0 {
 		return
 	}
-	m.YOffset = max(0, m.YOffset-n)
 
 	if m.UseInternalRenderer {
-		m.r.insertTop(m.lines[m.YOffset])
+		top := max(m.YOffset-n, 0)
+		bottom := min(top+n, len(m.lines))
+		m.r.insertTop(m.lines[top:bottom])
 	}
+
+	m.YOffset = max(m.YOffset-n, 0)
 }
 
 // UPDATE
@@ -214,7 +288,3 @@ func max(a, b int) int {
 func clamp(val, low, high int) int {
 	return max(low, min(high, val))
 }
-
-func bounded(s []string, start, end int) []string {
-	return s[clamp(start, 0, len(s)):clamp(end, 0, len(s))]
-}