Add more --border options

Instead of drawing the window border in Vim using an extra window,
extend the --border option so that we do can it natively.

Close #2223
Fix #2184

src/tui/light.go

@@ -653,15 +653,46 @@ func (w *LightWindow) drawBorder() {
 	case BorderRounded, BorderSharp:
 		w.drawBorderAround()
 	case BorderHorizontal:
-		w.drawBorderHorizontal()
+		w.drawBorderHorizontal(true, true)
+	case BorderVertical:
+		w.drawBorderVertical(true, true)
+	case BorderTop:
+		w.drawBorderHorizontal(true, false)
+	case BorderBottom:
+		w.drawBorderHorizontal(false, true)
+	case BorderLeft:
+		w.drawBorderVertical(true, false)
+	case BorderRight:
+		w.drawBorderVertical(false, true)
 	}
 }
 
-func (w *LightWindow) drawBorderHorizontal() {
-	w.Move(0, 0)
-	w.CPrint(ColBorder, repeat(w.border.horizontal, w.width))
-	w.Move(w.height-1, 0)
-	w.CPrint(ColBorder, repeat(w.border.horizontal, w.width))
+func (w *LightWindow) drawBorderHorizontal(top, bottom bool) {
+	if top {
+		w.Move(0, 0)
+		w.CPrint(ColBorder, repeat(w.border.horizontal, w.width))
+	}
+	if bottom {
+		w.Move(w.height-1, 0)
+		w.CPrint(ColBorder, repeat(w.border.horizontal, w.width))
+	}
+}
+
+func (w *LightWindow) drawBorderVertical(left, right bool) {
+	width := w.width - 2
+	if !left || !right {
+		width++
+	}
+	for y := 0; y < w.height; y++ {
+		w.Move(y, 0)
+		if left {
+			w.CPrint(ColBorder, string(w.border.vertical))
+		}
+		w.CPrint(ColBorder, repeat(' ', width))
+		if right {
+			w.CPrint(ColBorder, string(w.border.vertical))
+		}
+	}
 }
 
 func (w *LightWindow) drawBorderAround() {

src/tui/tcell.go

@@ -583,7 +583,8 @@ func (w *TcellWindow) CFill(fg Color, bg Color, a Attr, str string) FillReturn {
 }
 
 func (w *TcellWindow) drawBorder() {
-	if w.borderStyle.shape == BorderNone {
+	shape := w.borderStyle.shape
+	if shape == BorderNone {
 		return
 	}
 
@@ -603,17 +604,32 @@ func (w *TcellWindow) drawBorder() {
 		style = w.normal.style()
 	}
 
-	for x := left; x < right; x++ {
-		_screen.SetContent(x, top, w.borderStyle.horizontal, nil, style)
-		_screen.SetContent(x, bot-1, w.borderStyle.horizontal, nil, style)
+	switch shape {
+	case BorderRounded, BorderSharp, BorderHorizontal, BorderTop:
+		for x := left; x < right; x++ {
+			_screen.SetContent(x, top, w.borderStyle.horizontal, nil, style)
+		}
 	}
-
-	if w.borderStyle.shape != BorderHorizontal {
+	switch shape {
+	case BorderRounded, BorderSharp, BorderHorizontal, BorderBottom:
+		for x := left; x < right; x++ {
+			_screen.SetContent(x, bot-1, w.borderStyle.horizontal, nil, style)
+		}
+	}
+	switch shape {
+	case BorderRounded, BorderSharp, BorderVertical, BorderLeft:
 		for y := top; y < bot; y++ {
 			_screen.SetContent(left, y, w.borderStyle.vertical, nil, style)
+		}
+	}
+	switch shape {
+	case BorderRounded, BorderSharp, BorderVertical, BorderRight:
+		for y := top; y < bot; y++ {
 			_screen.SetContent(right-1, y, w.borderStyle.vertical, nil, style)
 		}
-
+	}
+	switch shape {
+	case BorderRounded, BorderSharp:
 		_screen.SetContent(left, top, w.borderStyle.topLeft, nil, style)
 		_screen.SetContent(right-1, top, w.borderStyle.topRight, nil, style)
 		_screen.SetContent(left, bot-1, w.borderStyle.bottomLeft, nil, style)

src/tui/tui.go

@@ -259,6 +259,11 @@ const (
 	BorderRounded
 	BorderSharp
 	BorderHorizontal
+	BorderVertical
+	BorderTop
+	BorderBottom
+	BorderLeft
+	BorderRight
 )
 
 type BorderStyle struct {