edit/ui: Add renderer for content with vertical scrollbar.

edit/ui/render.go

@@ -21,16 +21,27 @@ func Render(r Renderer, width int) *Buffer {
 	return bb.Buffer()
 }
 
-// NewStringRenderer returns a Renderer that shows the given string unstyled,
-// possibly trimmed to fit whatever width is available.
+// NewStringRenderer returns a Renderer that shows the given strings unstyled,
+// trimmed to fit whatever width is available.
 func NewStringRenderer(s string) Renderer {
-	return stringRenderer{s}
+	return NewLinesRenderer(s)
 }
 
-type stringRenderer struct{ s string }
+// NewLinesRenderer returns a Renderer that shows the given lines unstyled,
+// each trimmed to fit whatever width is available.
+func NewLinesRenderer(lines ...string) Renderer {
+	return linesRenderer{lines}
+}
 
-func (r stringRenderer) Render(bb *BufferBuilder) {
-	bb.WriteString(util.TrimWcwidth(r.s, bb.Width), "")
+type linesRenderer struct{ lines []string }
+
+func (r linesRenderer) Render(bb *BufferBuilder) {
+	for i, line := range r.lines {
+		if i > 0 {
+			bb.Newline()
+		}
+		bb.WriteString(util.TrimWcwidth(line, bb.Width), "")
+	}
 }
 
 // NewModeLineRenderer returns a Renderer for a mode line.
@@ -47,7 +58,7 @@ func (ml modeLineRenderer) Render(bb *BufferBuilder) {
 	bb.WriteString(ml.title, styleForMode.String())
 	bb.WriteSpaces(1, "")
 	bb.WriteString(ml.filter, styleForFilter.String())
-	bb.Dot = bb.Cursor()
+	bb.SetDotToCursor()
 }
 
 // NewModeLineWithScrollBarRenderer returns a Renderer for a mode line with a
@@ -72,3 +83,21 @@ func (ml modeLineWithScrollBarRenderer) Render(bb *BufferBuilder) {
 		writeHorizontalScrollbar(bb, ml.n, ml.low, ml.high, scrollbarWidth)
 	}
 }
+
+// NewRendererWithVerticalScrollbar returns a Renderer that renders the given
+// base plus a vertical scrollbar at the right-hand side.
+func NewRendererWithVerticalScrollbar(base Renderer, n, low, high int) Renderer {
+	return rendererWithVerticalScrollbar{base, n, low, high}
+}
+
+type rendererWithVerticalScrollbar struct {
+	base         Renderer
+	n, low, high int
+}
+
+func (r rendererWithVerticalScrollbar) Render(bb *BufferBuilder) {
+	bufBase := Render(r.base, bb.Width-1)
+	bb.ExtendRight(bufBase, 0)
+	bufScrollbar := renderVerticalScrollbar(r.n, r.low, r.high, len(bufBase.Lines))
+	bb.ExtendRight(bufScrollbar, bb.Width-1)
+}

edit/ui/render_test.go

@@ -22,6 +22,15 @@ func TestRender(t *testing.T) {
 		Args(NewStringRenderer("string"), 3).
 			Rets(NewBufferBuilder(3).WriteString("str", "").Buffer()),
 
+		Args(NewLinesRenderer("line 1", "line 2"), 10).
+			Rets(
+				NewBufferBuilder(10).WriteString("line 1", "").Newline().
+					WriteString("line 2", "").Buffer()),
+		Args(NewLinesRenderer("line 1", "line 2"), 3).
+			Rets(
+				NewBufferBuilder(3).WriteString("lin", "").Newline().
+					WriteString("lin", "").Buffer()),
+
 		Args(NewModeLineRenderer("M", "f"), 10).
 			Rets(
 				NewBufferBuilder(10).
@@ -43,5 +52,18 @@ func TestRender(t *testing.T) {
 					Write(' ', styleForScrollBarThumb.String()).
 					WriteString("━━━━", styleForScrollBarArea.String()).
 					Buffer()),
+
+		Args(NewRendererWithVerticalScrollbar(NewLinesRenderer("1", "2", "3"), 3, 0, 1), 5).
+			Rets(
+				NewBufferBuilder(5).
+					WriteString("1   ", "").
+					Write(' ', styleForScrollBarThumb.String()).
+					Newline().
+					WriteString("2   ", "").
+					Write('│', styleForScrollBarArea.String()).
+					Newline().
+					WriteString("3   ", "").
+					Write('│', styleForScrollBarArea.String()).
+					Buffer()),
 	})
 }

edit/ui/scrollbar.go

@@ -11,6 +11,22 @@ func writeHorizontalScrollbar(bb *BufferBuilder, n, low, high, width int) {
 	}
 }
 
+func renderVerticalScrollbar(n, low, high, height int) *Buffer {
+	slow, shigh := findScrollInterval(n, low, high, height)
+	bb := NewBufferBuilder(1)
+	for i := 0; i < height; i++ {
+		if i > 0 {
+			bb.Newline()
+		}
+		if slow <= i && i < shigh {
+			bb.Write(' ', styleForScrollBarThumb.String())
+		} else {
+			bb.Write('│', styleForScrollBarArea.String())
+		}
+	}
+	return bb.Buffer()
+}
+
 func findScrollInterval(n, low, high, height int) (int, int) {
 	f := func(i int) int {
 		return int(float64(i)/float64(n)*float64(height) + 0.5)