Add new border style: 'thinblock' (#3327)

Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>

7 files changed, 56 insertions, 13 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1534a515..fbc8222b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,19 @@
 CHANGELOG
 =========
 
+0.41.2
+------
+- Added new border style `thinblock` which uses symbols for legacy computing
+  [one eighth block elements](https://en.wikipedia.org/wiki/Symbols_for_Legacy_Computing)
+    - Similarly to `block`, this style is suitable when using a different
+      background color because the window is completely contained within the border.
+      ```sh
+      fzf --preview 'cat {}' --border thinblock --preview-window border-thinblock \
+          --color border:233,bg:234,separator:235,preview-border:235,preview-bg:236
+      ```
+    - This style may not render correctly depending on the font and the
+      terminal emulator.
+
 0.41.1
 ------
 - Fixed a bug where preview window is not updated when `--disabled` is set and
diff --git a/man/man1/fzf.1 b/man/man1/fzf.1
index dda21069..518f1a6e 100644
--- a/man/man1/fzf.1
+++ b/man/man1/fzf.1
@@ -228,6 +228,10 @@ Draw border around the finder
 .br
 .BR double "        Border with double lines"
 .br
+.BR block "         Border using block elements; suitable when using different background colors"
+.br
+.BR thinblock "     Border using legacy computing symbols; may not be displayed on some terminals"
+.br
 .BR horizontal "    Horizontal lines above and below the finder"
 .br
 .BR vertical "      Vertical lines on each side of the finder"
@@ -599,6 +603,10 @@ Should be used with one of the following \fB--preview-window\fR options.
 .br
 .B * border-double
 .br
+.B * border-block
+.br
+.B * border-thinblock
+.br
 .B * border-horizontal
 .br
 .B * border-top
diff --git a/src/options.go b/src/options.go
index 4db34640..69e5db91 100644
--- a/src/options.go
+++ b/src/options.go
@@ -63,7 +63,7 @@ const usage = `usage: fzf [options]
                            (default: 10)
     --layout=LAYOUT        Choose layout: [default|reverse|reverse-list]
     --border[=STYLE]       Draw border around the finder
-                           [rounded|sharp|bold|block|double|horizontal|vertical|
+                           [rounded|sharp|bold|block|thinblock|double|horizontal|vertical|
                             top|bottom|left|right|none] (default: rounded)
     --border-label=LABEL   Label to print on the border
     --border-label-pos=COL Position of the border label
@@ -546,6 +546,8 @@ func parseBorder(str string, optional bool) tui.BorderShape {
 		return tui.BorderBold
 	case "block":
 		return tui.BorderBlock
+	case "thinblock":
+		return tui.BorderThinBlock
 	case "double":
 		return tui.BorderDouble
 	case "horizontal":
@@ -566,7 +568,7 @@ func parseBorder(str string, optional bool) tui.BorderShape {
 		if optional && str == "" {
 			return tui.DefaultBorderShape
 		}
-		errorExit("invalid border style (expected: rounded|sharp|bold|block|double|horizontal|vertical|top|bottom|left|right|none)")
+		errorExit("invalid border style (expected: rounded|sharp|bold|block|thinblock|double|horizontal|vertical|top|bottom|left|right|none)")
 	}
 	return tui.BorderNone
 }
@@ -1438,6 +1440,8 @@ func parsePreviewWindowImpl(opts *previewOpts, input string, exit func(string))
 			opts.border = tui.BorderBold
 		case "border-block":
 			opts.border = tui.BorderBlock
+		case "border-thinblock":
+			opts.border = tui.BorderThinBlock
 		case "border-double":
 			opts.border = tui.BorderDouble
 		case "noborder", "border-none":
diff --git a/src/terminal.go b/src/terminal.go
index 3179d929..b60424ba 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -727,7 +727,7 @@ func (t *Terminal) environ() []string {
 
 func borderLines(shape tui.BorderShape) int {
 	switch shape {
-	case tui.BorderHorizontal, tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderBlock, tui.BorderDouble:
+	case tui.BorderHorizontal, tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderBlock, tui.BorderThinBlock, tui.BorderDouble:
 		return 2
 	case tui.BorderTop, tui.BorderBottom:
 		return 1
@@ -1085,7 +1085,7 @@ func (t *Terminal) adjustMarginAndPadding() (int, int, [4]int, [4]int) {
 			if idx == 3 {
 				extraMargin[idx] += 1 + bw
 			}
-		case tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderBlock, tui.BorderDouble:
+		case tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderBlock, tui.BorderThinBlock, tui.BorderDouble:
 			extraMargin[idx] += 1 + bw*(idx%2)
 		}
 		marginInt[idx] = sizeSpecToInt(idx, sizeSpec) + extraMargin[idx]
@@ -1178,7 +1178,7 @@ func (t *Terminal) resizeWindows(forcePreview bool) {
 		t.border = t.tui.NewWindow(
 			marginInt[0], marginInt[3], width+(1+bw), height,
 			false, tui.MakeBorderStyle(tui.BorderRight, t.unicode))
-	case tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderBlock, tui.BorderDouble:
+	case tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderBlock, tui.BorderThinBlock, tui.BorderDouble:
 		t.border = t.tui.NewWindow(
 			marginInt[0]-1, marginInt[3]-(1+bw), width+(1+bw)*2, height+2,
 			false, tui.MakeBorderStyle(t.borderShape, t.unicode))
@@ -1212,7 +1212,7 @@ func (t *Terminal) resizeWindows(forcePreview bool) {
 				}
 				t.pborder = t.tui.NewWindow(y, x, w, h, true, previewBorder)
 				switch previewOpts.border {
-				case tui.BorderSharp, tui.BorderRounded, tui.BorderBold, tui.BorderBlock, tui.BorderDouble:
+				case tui.BorderSharp, tui.BorderRounded, tui.BorderBold, tui.BorderBlock, tui.BorderThinBlock, tui.BorderDouble:
 					pwidth -= (1 + bw) * 2
 					pheight -= 2
 					x += 1 + bw
@@ -1356,7 +1356,7 @@ func (t *Terminal) printLabel(window tui.Window, render labelPrinter, opts label
 	}
 
 	switch borderShape {
-	case tui.BorderHorizontal, tui.BorderTop, tui.BorderBottom, tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderBlock, tui.BorderDouble:
+	case tui.BorderHorizontal, tui.BorderTop, tui.BorderBottom, tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderBlock, tui.BorderThinBlock, tui.BorderDouble:
 		if redrawBorder {
 			window.DrawHBorder()
 		}
diff --git a/src/tui/light.go b/src/tui/light.go
index 8356eb50..cff59c90 100644
--- a/src/tui/light.go
+++ b/src/tui/light.go
@@ -757,7 +757,7 @@ func (w *LightWindow) DrawHBorder() {
 
 func (w *LightWindow) drawBorder(onlyHorizontal bool) {
 	switch w.border.shape {
-	case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderDouble:
+	case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderThinBlock, BorderDouble:
 		w.drawBorderAround(onlyHorizontal)
 	case BorderHorizontal:
 		w.drawBorderHorizontal(true, true)
diff --git a/src/tui/tcell.go b/src/tui/tcell.go
index f815df07..8f6806d4 100644
--- a/src/tui/tcell.go
+++ b/src/tui/tcell.go
@@ -715,7 +715,7 @@ func (w *TcellWindow) drawBorder(onlyHorizontal bool) {
 
 	hw := runewidth.RuneWidth(w.borderStyle.top)
 	switch shape {
-	case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderDouble, BorderHorizontal, BorderTop:
+	case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderThinBlock, BorderDouble, BorderHorizontal, BorderTop:
 		max := right - 2*hw
 		if shape == BorderHorizontal || shape == BorderTop {
 			max = right - hw
@@ -730,7 +730,7 @@ func (w *TcellWindow) drawBorder(onlyHorizontal bool) {
 		}
 	}
 	switch shape {
-	case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderDouble, BorderHorizontal, BorderBottom:
+	case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderThinBlock, BorderDouble, BorderHorizontal, BorderBottom:
 		max := right - 2*hw
 		if shape == BorderHorizontal || shape == BorderBottom {
 			max = right - hw
@@ -741,13 +741,13 @@ func (w *TcellWindow) drawBorder(onlyHorizontal bool) {
 	}
 	if !onlyHorizontal {
 		switch shape {
-		case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderDouble, BorderVertical, BorderLeft:
+		case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderThinBlock, BorderDouble, BorderVertical, BorderLeft:
 			for y := top; y < bot; y++ {
 				_screen.SetContent(left, y, w.borderStyle.left, nil, style)
 			}
 		}
 		switch shape {
-		case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderDouble, BorderVertical, BorderRight:
+		case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderThinBlock, BorderDouble, BorderVertical, BorderRight:
 			vw := runewidth.RuneWidth(w.borderStyle.right)
 			for y := top; y < bot; y++ {
 				_screen.SetContent(right-vw, y, w.borderStyle.right, nil, style)
@@ -755,7 +755,7 @@ func (w *TcellWindow) drawBorder(onlyHorizontal bool) {
 		}
 	}
 	switch shape {
-	case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderDouble:
+	case BorderRounded, BorderSharp, BorderBold, BorderBlock, BorderThinBlock, BorderDouble:
 		_screen.SetContent(left, top, w.borderStyle.topLeft, 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)
diff --git a/src/tui/tui.go b/src/tui/tui.go
index 55fbe771..8cfe8d33 100644
--- a/src/tui/tui.go
+++ b/src/tui/tui.go
@@ -315,6 +315,7 @@ const (
 	BorderSharp
 	BorderBold
 	BorderBlock
+	BorderThinBlock
 	BorderDouble
 	BorderHorizontal
 	BorderVertical
@@ -408,6 +409,23 @@ func MakeBorderStyle(shape BorderShape, unicode bool) BorderStyle {
 			bottomLeft:  '▙',
 			bottomRight: '▟',
 		}
+
+	case BorderThinBlock:
+		// 🭽▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔🭾
+		// ▏                  ▕
+		// 🭼▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁🭿
+		return BorderStyle{
+			shape:       shape,
+			top:         '▔',
+			bottom:      '▁',
+			left:        '▏',
+			right:       '▕',
+			topLeft:     '🭽',
+			topRight:    '🭾',
+			bottomLeft:  '🭼',
+			bottomRight: '🭿',
+		}
+
 	case BorderDouble:
 		return BorderStyle{
 			shape:       shape,