Better support for Windows terminals

* Default border style on Windows is changed to `sharp` because some
  Windows terminals are not capable of displaying `rounded` border
  characters correctly.
* If your terminal emulator renders each box-drawing character with
  2 columns, set `RUNEWIDTH_EASTASIAN` environment variable to `1`.

4 files changed, 30 insertions, 10 deletions

diff --git a/src/tui/dummy.go b/src/tui/dummy.go
index adecd6fc..7a02a8af 100644
--- a/src/tui/dummy.go
+++ b/src/tui/dummy.go
@@ -8,6 +8,8 @@ func HasFullscreenRenderer() bool {
 	return false
 }
 
+var DefaultBorderShape BorderShape = BorderRounded
+
 func (a Attr) Merge(b Attr) Attr {
 	return a | b
 }
@@ -32,6 +34,7 @@ func (r *FullscreenRenderer) Resize(maxHeightFunc func(int) int) {}
 func (r *FullscreenRenderer) Pause(bool)                         {}
 func (r *FullscreenRenderer) Resume(bool, bool)                  {}
 func (r *FullscreenRenderer) Clear()                             {}
+func (r *FullscreenRenderer) NeedScrollbarRedraw() bool          { return false }
 func (r *FullscreenRenderer) Refresh()                           {}
 func (r *FullscreenRenderer) Close()                             {}
 
diff --git a/src/tui/light.go b/src/tui/light.go
index c41de480..578118b7 100644
--- a/src/tui/light.go
+++ b/src/tui/light.go
@@ -651,6 +651,10 @@ func (r *LightRenderer) Clear() {
 	r.flush()
 }
 
+func (r *LightRenderer) NeedScrollbarRedraw() bool {
+	return false
+}
+
 func (r *LightRenderer) RefreshWindows(windows []Window) {
 	r.flush()
 }
@@ -743,13 +747,14 @@ func (w *LightWindow) drawBorderHorizontal(top, bottom bool) {
 	if w.preview {
 		color = ColPreviewBorder
 	}
+	hw := runewidth.RuneWidth(w.border.horizontal)
 	if top {
 		w.Move(0, 0)
-		w.CPrint(color, repeat(w.border.horizontal, w.width))
+		w.CPrint(color, repeat(w.border.horizontal, w.width/hw))
 	}
 	if bottom {
 		w.Move(w.height-1, 0)
-		w.CPrint(color, repeat(w.border.horizontal, w.width))
+		w.CPrint(color, repeat(w.border.horizontal, w.width/hw))
 	}
 }
 
@@ -780,15 +785,19 @@ func (w *LightWindow) drawBorderAround() {
 	if w.preview {
 		color = ColPreviewBorder
 	}
-	w.CPrint(color, string(w.border.topLeft)+repeat(w.border.horizontal, w.width-2)+string(w.border.topRight))
+	hw := runewidth.RuneWidth(w.border.horizontal)
+	vw := runewidth.RuneWidth(w.border.vertical)
+	tcw := runewidth.RuneWidth(w.border.topLeft) + runewidth.RuneWidth(w.border.topRight)
+	bcw := runewidth.RuneWidth(w.border.bottomLeft) + runewidth.RuneWidth(w.border.bottomRight)
+	w.CPrint(color, string(w.border.topLeft)+repeat(w.border.horizontal, (w.width-tcw)/hw)+string(w.border.topRight))
 	for y := 1; y < w.height-1; y++ {
 		w.Move(y, 0)
 		w.CPrint(color, string(w.border.vertical))
-		w.CPrint(color, repeat(' ', w.width-2))
+		w.CPrint(color, repeat(' ', w.width-vw*2))
 		w.CPrint(color, string(w.border.vertical))
 	}
 	w.Move(w.height-1, 0)
-	w.CPrint(color, string(w.border.bottomLeft)+repeat(w.border.horizontal, w.width-2)+string(w.border.bottomRight))
+	w.CPrint(color, string(w.border.bottomLeft)+repeat(w.border.horizontal, (w.width-bcw)/hw)+string(w.border.bottomRight))
 }
 
 func (w *LightWindow) csi(code string) {
diff --git a/src/tui/tcell.go b/src/tui/tcell.go
index 82d72995..f1f18e24 100644
--- a/src/tui/tcell.go
+++ b/src/tui/tcell.go
@@ -17,6 +17,8 @@ func HasFullscreenRenderer() bool {
 	return true
 }
 
+var DefaultBorderShape BorderShape = BorderSharp
+
 func asTcellColor(color Color) tcell.Color {
 	if color == colDefault {
 		return tcell.ColorDefault
@@ -187,6 +189,10 @@ func (r *FullscreenRenderer) Clear() {
 	_screen.Clear()
 }
 
+func (r *FullscreenRenderer) NeedScrollbarRedraw() bool {
+	return true
+}
+
 func (r *FullscreenRenderer) Refresh() {
 	// noop
 }
@@ -686,15 +692,16 @@ func (w *TcellWindow) drawBorder() {
 		style = w.normal.style()
 	}
 
+	hw := runewidth.RuneWidth(w.borderStyle.horizontal)
 	switch shape {
 	case BorderRounded, BorderSharp, BorderBold, BorderDouble, BorderHorizontal, BorderTop:
-		for x := left; x < right; x++ {
+		for x := left; x <= right-hw; x += hw {
 			_screen.SetContent(x, top, w.borderStyle.horizontal, nil, style)
 		}
 	}
 	switch shape {
 	case BorderRounded, BorderSharp, BorderBold, BorderDouble, BorderHorizontal, BorderBottom:
-		for x := left; x < right; x++ {
+		for x := left; x <= right-hw; x += hw {
 			_screen.SetContent(x, bot-1, w.borderStyle.horizontal, nil, style)
 		}
 	}
@@ -707,14 +714,14 @@ func (w *TcellWindow) drawBorder() {
 	switch shape {
 	case BorderRounded, BorderSharp, BorderBold, BorderDouble, BorderVertical, BorderRight:
 		for y := top; y < bot; y++ {
-			_screen.SetContent(right-1, y, w.borderStyle.vertical, nil, style)
+			_screen.SetContent(right-hw, y, w.borderStyle.vertical, nil, style)
 		}
 	}
 	switch shape {
 	case BorderRounded, BorderSharp, BorderBold, BorderDouble:
 		_screen.SetContent(left, top, w.borderStyle.topLeft, nil, style)
-		_screen.SetContent(right-1, top, w.borderStyle.topRight, nil, style)
+		_screen.SetContent(right-runewidth.RuneWidth(w.borderStyle.topRight), top, w.borderStyle.topRight, nil, style)
 		_screen.SetContent(left, bot-1, w.borderStyle.bottomLeft, nil, style)
-		_screen.SetContent(right-1, bot-1, w.borderStyle.bottomRight, nil, style)
+		_screen.SetContent(right-runewidth.RuneWidth(w.borderStyle.bottomRight), bot-1, w.borderStyle.bottomRight, nil, style)
 	}
 }
diff --git a/src/tui/tui.go b/src/tui/tui.go
index c6a65d82..5a86453b 100644
--- a/src/tui/tui.go
+++ b/src/tui/tui.go
@@ -410,6 +410,7 @@ type Renderer interface {
 	RefreshWindows(windows []Window)
 	Refresh()
 	Close()
+	NeedScrollbarRedraw() bool
 
 	GetChar() Event