Add --ellipsis=.. option

Close #2432

Also see
- #1769
- https://github.com/junegunn/fzf/pull/1844#issuecomment-586663660

4 files changed, 73 insertions, 20 deletions

diff --git a/src/options.go b/src/options.go
index b3bcdeab..cc77143d 100644
--- a/src/options.go
+++ b/src/options.go
@@ -70,6 +70,7 @@ const usage = `usage: fzf [options]
     --header=STR          String to print as header
     --header-lines=N      The first N lines of the input are treated as header
     --header-first        Print header before the prompt line
+    --ellipsis=STR        Ellipsis to show when line is truncated (default: '..')
 
   Display
     --ansi                Enable processing of ANSI color codes
@@ -235,6 +236,7 @@ type Options struct {
 	Header      []string
 	HeaderLines int
 	HeaderFirst bool
+	Ellipsis    string
 	Margin      [4]sizeSpec
 	Padding     [4]sizeSpec
 	BorderShape tui.BorderShape
@@ -298,6 +300,7 @@ func defaultOptions() *Options {
 		Header:      make([]string, 0),
 		HeaderLines: 0,
 		HeaderFirst: false,
+		Ellipsis:    "..",
 		Margin:      defaultMargin(),
 		Padding:     defaultMargin(),
 		Unicode:     true,
@@ -1280,6 +1283,7 @@ func parseOptions(opts *Options, allArgs []string) {
 	validateJumpLabels := false
 	validatePointer := false
 	validateMarker := false
+	validateEllipsis := false
 	for i := 0; i < len(allArgs); i++ {
 		arg := allArgs[i]
 		switch arg {
@@ -1465,6 +1469,9 @@ func parseOptions(opts *Options, allArgs []string) {
 			opts.HeaderFirst = true
 		case "--no-header-first":
 			opts.HeaderFirst = false
+		case "--ellipsis":
+			opts.Ellipsis = nextString(allArgs, &i, "ellipsis string required")
+			validateEllipsis = true
 		case "--preview":
 			opts.Preview.command = nextString(allArgs, &i, "preview command required")
 		case "--no-preview":
@@ -1562,6 +1569,9 @@ func parseOptions(opts *Options, allArgs []string) {
 				opts.Header = strLines(value)
 			} else if match, value := optString(arg, "--header-lines="); match {
 				opts.HeaderLines = atoi(value)
+			} else if match, value := optString(arg, "--ellipsis="); match {
+				opts.Ellipsis = value
+				validateEllipsis = true
 			} else if match, value := optString(arg, "--preview="); match {
 				opts.Preview.command = value
 			} else if match, value := optString(arg, "--preview-window="); match {
@@ -1624,6 +1634,14 @@ func parseOptions(opts *Options, allArgs []string) {
 			errorExit(err.Error())
 		}
 	}
+
+	if validateEllipsis {
+		for _, r := range opts.Ellipsis {
+			if !unicode.IsGraphic(r) {
+				errorExit("invalid character in ellipsis")
+			}
+		}
+	}
 }
 
 func validateSign(sign string, signOptName string) error {
diff --git a/src/terminal.go b/src/terminal.go
index e4823ad5..9ea0c1a9 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -50,7 +50,6 @@ var offsetComponentRegex *regexp.Regexp
 var offsetTrimCharsRegex *regexp.Regexp
 var activeTempFiles []string
 
-const ellipsis string = ".."
 const clearCode string = "\x1b[2J"
 
 func init() {
@@ -145,6 +144,7 @@ type Terminal struct {
 	headerLines        int
 	header             []string
 	header0            []string
+	ellipsis           string
 	ansi               bool
 	tabstop            int
 	margin             [4]sizeSpec
@@ -541,6 +541,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		headerLines:        opts.HeaderLines,
 		header:             header,
 		header0:            header,
+		ellipsis:           opts.Ellipsis,
 		ansi:               opts.Ansi,
 		tabstop:            opts.Tabstop,
 		reading:            true,
@@ -1261,47 +1262,54 @@ func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMat
 
 	offsets := result.colorOffsets(charOffsets, t.theme, colBase, colMatch, current)
 	maxWidth := t.window.Width() - (t.pointerLen + t.markerLen + 1)
-	maxe = util.Constrain(maxe+util.Min(maxWidth/2-2, t.hscrollOff), 0, len(text))
+	ellipsis, ellipsisWidth := util.Truncate(t.ellipsis, maxWidth/2)
+	maxe = util.Constrain(maxe+util.Min(maxWidth/2-ellipsisWidth, t.hscrollOff), 0, len(text))
 	displayWidth := t.displayWidthWithLimit(text, 0, maxWidth)
 	if displayWidth > maxWidth {
-		transformOffsets := func(diff int32) {
+		transformOffsets := func(diff int32, rightTrim bool) {
 			for idx, offset := range offsets {
 				b, e := offset.offset[0], offset.offset[1]
-				b += 2 - diff
-				e += 2 - diff
-				b = util.Max32(b, 2)
+				el := int32(len(ellipsis))
+				b += el - diff
+				e += el - diff
+				b = util.Max32(b, el)
+				if rightTrim {
+					e = util.Min32(e, int32(maxWidth-ellipsisWidth))
+				}
 				offsets[idx].offset[0] = b
 				offsets[idx].offset[1] = util.Max32(b, e)
 			}
 		}
 		if t.hscroll {
 			if t.keepRight && pos == nil {
-				trimmed, diff := t.trimLeft(text, maxWidth-2)
-				transformOffsets(diff)
-				text = append([]rune(ellipsis), trimmed...)
-			} else if !t.overflow(text[:maxe], maxWidth-2) {
+				trimmed, diff := t.trimLeft(text, maxWidth-ellipsisWidth)
+				transformOffsets(diff, false)
+				text = append(ellipsis, trimmed...)
+			} else if !t.overflow(text[:maxe], maxWidth-ellipsisWidth) {
 				// Stri..
-				text, _ = t.trimRight(text, maxWidth-2)
-				text = append(text, []rune(ellipsis)...)
+				text, _ = t.trimRight(text, maxWidth-ellipsisWidth)
+				text = append(text, ellipsis...)
 			} else {
 				// Stri..
-				if t.overflow(text[maxe:], 2) {
-					text = append(text[:maxe], []rune(ellipsis)...)
+				rightTrim := false
+				if t.overflow(text[maxe:], ellipsisWidth) {
+					text = append(text[:maxe], ellipsis...)
+					rightTrim = true
 				}
 				// ..ri..
 				var diff int32
-				text, diff = t.trimLeft(text, maxWidth-2)
+				text, diff = t.trimLeft(text, maxWidth-ellipsisWidth)
 
 				// Transform offsets
-				transformOffsets(diff)
-				text = append([]rune(ellipsis), text...)
+				transformOffsets(diff, rightTrim)
+				text = append(ellipsis, text...)
 			}
 		} else {
-			text, _ = t.trimRight(text, maxWidth-2)
-			text = append(text, []rune(ellipsis)...)
+			text, _ = t.trimRight(text, maxWidth-ellipsisWidth)
+			text = append(text, ellipsis...)
 
 			for idx, offset := range offsets {
-				offsets[idx].offset[0] = util.Min32(offset.offset[0], int32(maxWidth-2))
+				offsets[idx].offset[0] = util.Min32(offset.offset[0], int32(maxWidth-len(ellipsis)))
 				offsets[idx].offset[1] = util.Min32(offset.offset[1], int32(maxWidth))
 			}
 		}
diff --git a/src/util/util.go b/src/util/util.go
index c3995bfd..a1c37f7a 100644
--- a/src/util/util.go
+++ b/src/util/util.go
@@ -34,6 +34,23 @@ func RunesWidth(runes []rune, prefixWidth int, tabstop int, limit int) (int, int
 	return width, -1
 }
 
+// Truncate returns the truncated runes and its width
+func Truncate(input string, limit int) ([]rune, int) {
+	runes := []rune{}
+	width := 0
+	gr := uniseg.NewGraphemes(input)
+	for gr.Next() {
+		rs := gr.Runes()
+		w := runewidth.StringWidth(string(rs))
+		if width+w > limit {
+			return runes, width
+		}
+		width += w
+		runes = append(runes, rs...)
+	}
+	return runes, width
+}
+
 // Max returns the largest integer
 func Max(first int, second int) int {
 	if first >= second {
diff --git a/src/util/util_test.go b/src/util/util_test.go
index 45a5a2d0..20bdb92a 100644
--- a/src/util/util_test.go
+++ b/src/util/util_test.go
@@ -54,3 +54,13 @@ func TestRunesWidth(t *testing.T) {
 		}
 	}
 }
+
+func TestTruncate(t *testing.T) {
+	truncated, width := Truncate("가나다라마", 7)
+	if string(truncated) != "가나다" {
+		t.Errorf("Expected: 가나다, actual: %s", string(truncated))
+	}
+	if width != 6 {
+		t.Errorf("Expected: 6, actual: %d", width)
+	}
+}