Add gap line

Close #4182

4 files changed, 66 insertions, 10 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3e30749b..75e873b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -61,6 +61,16 @@ Also, fzf now offers "style presets" for quick customization, which can be activ
         - `transform-header-label`
 - Added `--preview-border[=STYLE]` as short for `--preview-window=border[-STYLE]`
 - Added new preview border style `line` which draws a single separator line between the preview window and the rest of the interface
+- fzf will now render a dashed line (`┈┈`) in each `--gap` for better visual separation.
+  ```sh
+  # All bash/zsh functions, highlighted
+  declare -f |
+    perl -0 -pe 's/^}\n/}\0/gm' |
+    bat --plain --language bash --color always |
+    fzf --read0 --ansi --layout reverse --multi --highlight-line \
+        --gap
+  ```
+    * You can customize the line using `--gap-line[=STR]`.
 - You can specify `border-native` to `--tmux` so that native tmux border is used instead of `--border`. This can be useful if you start a different program from inside the popup.
   ```sh
   fzf --tmux border-native --bind 'enter:execute:less {}'
diff --git a/src/options.go b/src/options.go
index 3932cb56..470d3081 100644
--- a/src/options.go
+++ b/src/options.go
@@ -582,6 +582,7 @@ type Options struct {
 	HeaderLines       int
 	HeaderFirst       bool
 	Gap               int
+	GapLine           *string
 	Ellipsis          *string
 	Scrollbar         *string
 	Margin            [4]sizeSpec
@@ -2567,6 +2568,15 @@ func parseOptions(index *int, opts *Options, allArgs []string) error {
 			}
 		case "--no-gap":
 			opts.Gap = 0
+		case "--gap-line":
+			if given, bar := optionalNextString(); given {
+				opts.GapLine = &bar
+			} else {
+				opts.GapLine = nil
+			}
+		case "--no-gap-line":
+			empty := ""
+			opts.GapLine = &empty
 		case "--ellipsis":
 			str, err := nextString("ellipsis string required")
 			if err != nil {
@@ -2987,6 +2997,14 @@ func postProcessOptions(opts *Options) error {
 		opts.Pointer = &defaultPointer
 	}
 
+	if opts.GapLine == nil {
+		defaultGapLine := "┈"
+		if !opts.Unicode {
+			defaultGapLine = "-"
+		}
+		opts.GapLine = &defaultGapLine
+	}
+
 	markerLen := 1
 	if opts.Marker == nil {
 		if opts.MarkerMulti != nil && opts.MarkerMulti[0] == "" {
diff --git a/src/terminal.go b/src/terminal.go
index d7ca89b6..2b86e010 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -267,6 +267,8 @@ type Terminal struct {
 	hscrollOff         int
 	scrollOff          int
 	gap                int
+	gapLine            labelPrinter
+	gapLineLen         int
 	wordRubout         string
 	wordNext           string
 	cx                 int
@@ -949,6 +951,11 @@ func NewTerminal(opts *Options, eventBox *util.EventBox, executor *util.Executor
 		t.separator, t.separatorLen = t.ansiLabelPrinter(bar, &tui.ColSeparator, true)
 	}
 
+	// Gap line
+	if t.gap > 0 && len(*opts.GapLine) > 0 {
+		t.gapLine, t.gapLineLen = t.ansiLabelPrinter(*opts.GapLine, &tui.ColListBorder, true)
+	}
+
 	if opts.Ellipsis != nil {
 		t.ellipsis = *opts.Ellipsis
 	} else if t.unicode {
@@ -2446,9 +2453,7 @@ func (t *Terminal) canSpanMultiLines() bool {
 	return t.multiLine || t.wrap || t.gap > 0
 }
 
-func (t *Terminal) renderEmptyLine(line int, barRange [2]int) {
-	t.move(line, 0, true)
-	t.markEmptyLine(line)
+func (t *Terminal) renderBar(line int, barRange [2]int) {
 	// If the screen is not filled with the list in non-multi-line mode,
 	// scrollbar is not visible at all. But in multi-line mode, we may need
 	// to redraw the scrollbar character at the end.
@@ -2457,6 +2462,29 @@ func (t *Terminal) renderEmptyLine(line int, barRange [2]int) {
 	}
 }
 
+func (t *Terminal) renderEmptyLine(line int, barRange [2]int) {
+	t.move(line, 0, true)
+	t.markEmptyLine(line)
+	t.renderBar(line, barRange)
+}
+
+func (t *Terminal) renderGapLine(line int, barRange [2]int, drawLine bool) {
+	t.move(line, 0, false)
+	t.window.CPrint(tui.ColCursorEmpty, t.pointerEmpty)
+	t.window.Print(t.markerEmpty)
+	x := t.pointerLen + t.markerLen
+
+	width := t.window.Width() - x - 1
+	if drawLine && t.gapLine != nil {
+		t.gapLine(t.window, width)
+	} else {
+		t.move(line, x, true)
+	}
+	t.markOtherLine(line)
+	t.renderBar(line, barRange)
+	t.prevLines[line].width = width
+}
+
 func (t *Terminal) printList() {
 	t.constrain()
 	barLength, barStart := t.getScrollbar()
@@ -2629,7 +2657,7 @@ func (t *Terminal) printItem(result Result, line int, maxLine int, index int, cu
 	}
 	for i := 0; i < t.gap && finalLineNum < maxLine; i++ {
 		finalLineNum++
-		t.renderEmptyLine(finalLineNum, barRange)
+		t.renderGapLine(finalLineNum, barRange, i == t.gap-1)
 	}
 	return finalLineNum
 }
diff --git a/test/test_go.rb b/test/test_go.rb
index 6a7f2ce4..2b5e0a24 100755
--- a/test/test_go.rb
+++ b/test/test_go.rb
@@ -3423,28 +3423,28 @@ class TestGoFZF < TestBase
       │ >
       │   100/100 ──────
       │ > 1
-      │
+      │   ┈┈┈┈┈┈┈┈┈┈┈┈┈┈
       │   2
-      │
+      │   ┈┈┈┈┈┈┈┈┈┈┈┈┈┈
       │   3
-      │
+      │   ┈┈┈┈┈┈┈┈┈┈┈┈┈┈
       │   4
     BLOCK
     tmux.until { assert_block(block, _1) }
   end
 
   def test_gap_2
-    tmux.send_keys %(seq 100 | #{FZF} --gap=2 --border --reverse), :Enter
+    tmux.send_keys %(seq 100 | #{FZF} --gap=2 --gap-line xyz --border --reverse), :Enter
     block = <<~BLOCK
       ╭─────────────────
       │ >
       │   100/100 ──────
       │ > 1
       │
-      │
+      │   xyzxyzxyzxyzxy
       │   2
       │
-      │
+      │   xyzxyzxyzxyzxy
       │   3
     BLOCK
     tmux.until { assert_block(block, _1) }