Add --freeze-left=N option to keep the leftmost N fields visible

CHANGELOG.md

@@ -1,6 +1,19 @@
 CHANGELOG
 =========
 
+0.67.0
+------
+- Added `--freeze-left=N` option to keep the leftmost N columns visible.
+  ```sh
+  # Keeps the file name column fixed and always visible
+  git grep --line-number --color=always -- '' |
+      fzf --ansi --delimiter : --freeze-left 1
+
+  # Used with --keep-right
+  git grep --line-number --color=always -- '' |
+      fzf --ansi --delimiter : --freeze-left 1 --keep-right
+  ```
+
 0.66.1
 ------
 - Bug fixes

man/man1/fzf.1

@@ -629,6 +629,9 @@ Render empty lines between each item
 The given string will be repeated to draw a horizontal line on each gap
 (default: '┈' or '\-' depending on \fB\-\-no\-unicode\fR).
 .TP
+.BI "\-\-freeze\-left=" "N"
+Number of fields to freeze on the left.
+.TP
 .B "\-\-keep\-right"
 Keep the right end of the line visible when it's too long. Effective only when
 the query string is empty.

src/options.go

@@ -104,6 +104,7 @@ Usage: fzf [options]
     --gap[=N]                Render empty lines between each item
     --gap-line[=STR]         Draw horizontal line on each gap using the string
                              (default: '┈' or '-')
+    --freeze-left=N          Number of fields to freeze on the left
     --keep-right             Keep the right end of the line visible on overflow
     --scroll-off=LINES       Number of screen lines to keep above or below when
                              scrolling to the top or to the bottom (default: 0)
@@ -562,6 +563,7 @@ type Options struct {
 	Case              Case
 	Normalize         bool
 	Nth               []Range
+	FreezeLeft        int
 	WithNth           func(Delimiter) func([]Token, int32) string
 	AcceptNth         func(Delimiter) func([]Token, int32) string
 	Delimiter         Delimiter
@@ -2695,6 +2697,10 @@ func parseOptions(index *int, opts *Options, allArgs []string) error {
 			if opts.Nth, err = splitNth(str); err != nil {
 				return err
 			}
+		case "--freeze-left":
+			if opts.FreezeLeft, err = nextInt("number of fields required"); err != nil {
+				return err
+			}
 		case "--with-nth":
 			str, err := nextString("nth expression required")
 			if err != nil {
@@ -3338,6 +3344,10 @@ func parseOptions(index *int, opts *Options, allArgs []string) error {
 		return errors.New("empty jump labels")
 	}
 
+	if opts.FreezeLeft < 0 {
+		return errors.New("number of fields to freeze must be a non-negative integer")
+	}
+
 	if validateJumpLabels {
 		for _, r := range opts.JumpLabels {
 			if r < 32 || r > 126 {

src/terminal.go

@@ -331,6 +331,7 @@ type Terminal struct {
 	scrollbar          string
 	previewScrollbar   string
 	ansi               bool
+	freezeLeft         int
 	nthAttr            tui.Attr
 	nth                []Range
 	nthCurrent         []Range
@@ -1050,6 +1051,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox, executor *util.Executor
 		footer:             opts.Footer,
 		header0:            opts.Header,
 		ansi:               opts.Ansi,
+		freezeLeft:         opts.FreezeLeft,
 		nthAttr:            opts.Theme.Nth.Attr,
 		nth:                opts.Nth,
 		nthCurrent:         opts.Nth,
@@ -3525,6 +3527,18 @@ func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMat
 	}
 	allOffsets := result.colorOffsets(charOffsets, nthOffsets, t.theme, colBase, colMatch, t.nthAttr, hidden)
 
+	// Determine split offset for horizontal scrolling with freeze
+	splitOffset := -1
+	if t.hscroll && !t.wrap && t.freezeLeft > 0 {
+		tokens := Tokenize(item.text.ToString(), t.delimiter)
+		if len(tokens) == 0 {
+			splitOffset = 0
+		} else {
+			token := tokens[util.Min(t.freezeLeft, len(tokens))-1]
+			splitOffset = int(token.prefixLength) + token.text.Length() - token.text.TrailingWhitespaces()
+		}
+	}
+
 	maxLines := 1
 	if t.canSpanMultiLines() {
 		maxLines = maxLineNum - lineNum + 1
@@ -3594,6 +3608,10 @@ func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMat
 				break
 			}
 		}
+		splitOffsetLocal := 0
+		if splitOffset >= 0 && splitOffset > from && splitOffset < from+len(line) {
+			splitOffsetLocal = splitOffset - from
+		}
 		from += len(line)
 		if lineOffset < skipLines {
 			continue
@@ -3667,69 +3685,88 @@ func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMat
 			wrapped = true
 		}
 
-		displayWidth = t.displayWidthWithLimit(line, 0, maxWidth)
-		if !t.wrap && displayWidth > maxWidth {
-			ellipsis, ellipsisWidth := util.Truncate(t.ellipsis, maxWidth/2)
-			maxe = util.Constrain(maxe+util.Min(maxWidth/2-ellipsisWidth, t.hscrollOff), 0, len(line))
-			transformOffsets := func(diff int32, rightTrim bool) {
-				for idx, offset := range offsets {
-					b, e := offset.offset[0], offset.offset[1]
-					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)
-				}
+		frozen := line[:splitOffsetLocal]
+		rest := line[splitOffsetLocal:]
+		displayWidthSum := 0
+		for fidx, runes := range [][]rune{frozen, rest} {
+			if len(runes) == 0 {
+				continue
 			}
-			if t.hscroll {
-				if t.keepRight && pos == nil {
-					trimmed, diff := t.trimLeft(line, maxWidth, ellipsisWidth)
-					transformOffsets(diff, false)
-					line = append(ellipsis, trimmed...)
-				} else if !t.overflow(line[:maxe], maxWidth-ellipsisWidth) {
-					// Stri..
-					line, _ = t.trimRight(line, maxWidth-ellipsisWidth)
-					line = append(line, ellipsis...)
+			if splitOffsetLocal > 0 && fidx == 1 {
+				for idx := range offsets {
+					offsets[idx].offset[0] -= int32(splitOffsetLocal)
+					offsets[idx].offset[1] -= int32(splitOffsetLocal)
+				}
+				maxe -= splitOffsetLocal
+			}
+			displayWidth = t.displayWidthWithLimit(runes, 0, maxWidth)
+			if !t.wrap && displayWidth > maxWidth {
+				ellipsis, ellipsisWidth := util.Truncate(t.ellipsis, maxWidth/2)
+				maxe = util.Constrain(maxe+util.Min(maxWidth/2-ellipsisWidth, t.hscrollOff), 0, len(runes))
+				transformOffsets := func(diff int32, rightTrim bool) {
+					for idx, offset := range offsets {
+						b, e := offset.offset[0], offset.offset[1]
+						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 fidx > 0 && t.keepRight && pos == nil {
+						trimmed, diff := t.trimLeft(runes, maxWidth, ellipsisWidth)
+						transformOffsets(diff, false)
+						runes = append(ellipsis, trimmed...)
+					} else if fidx == 0 || !t.overflow(runes[:maxe], maxWidth-ellipsisWidth) {
+						// Stri..
+						runes, _ = t.trimRight(runes, maxWidth-ellipsisWidth)
+						runes = append(runes, ellipsis...)
+					} else {
+						// Stri..
+						rightTrim := false
+						if t.overflow(runes[maxe:], ellipsisWidth) {
+							runes = append(runes[:maxe], ellipsis...)
+							rightTrim = true
+						}
+						// ..ri..
+						var diff int32
+						runes, diff = t.trimLeft(runes, maxWidth, ellipsisWidth)
+
+						// Transform offsets
+						transformOffsets(diff, rightTrim)
+						runes = append(ellipsis, runes...)
+					}
 				} else {
-					// Stri..
-					rightTrim := false
-					if t.overflow(line[maxe:], ellipsisWidth) {
-						line = append(line[:maxe], ellipsis...)
-						rightTrim = true
+					runes, _ = t.trimRight(runes, maxWidth-ellipsisWidth)
+					runes = append(runes, ellipsis...)
+
+					for idx, offset := range offsets {
+						offsets[idx].offset[0] = util.Min32(offset.offset[0], int32(maxWidth-len(ellipsis)))
+						offsets[idx].offset[1] = util.Min32(offset.offset[1], int32(maxWidth))
 					}
-					// ..ri..
-					var diff int32
-					line, diff = t.trimLeft(line, maxWidth, ellipsisWidth)
-
-					// Transform offsets
-					transformOffsets(diff, rightTrim)
-					line = append(ellipsis, line...)
 				}
+				displayWidth = t.displayWidthWithLimit(runes, 0, displayWidth)
+			}
+			displayWidthSum += displayWidth
+
+			if maxWidth > 0 {
+				color := colBase
+				if hidden {
+					color = color.WithFg(t.theme.Nomatch)
+				}
+				t.printColoredString(t.window, runes, offsets, color)
 			} else {
-				line, _ = t.trimRight(line, maxWidth-ellipsisWidth)
-				line = append(line, ellipsis...)
-
-				for idx, offset := range offsets {
-					offsets[idx].offset[0] = util.Min32(offset.offset[0], int32(maxWidth-len(ellipsis)))
-					offsets[idx].offset[1] = util.Min32(offset.offset[1], int32(maxWidth))
-				}
+				break
 			}
-			displayWidth = t.displayWidthWithLimit(line, 0, displayWidth)
-		}
-
-		if maxWidth > 0 {
-			color := colBase
-			if hidden {
-				color = color.WithFg(t.theme.Nomatch)
-			}
-			t.printColoredString(t.window, line, offsets, color)
+			maxWidth -= displayWidth
 		}
 		if postTask != nil {
-			postTask(actualLineNum, displayWidth, wasWrapped, forceRedraw, lbg)
+			postTask(actualLineNum, displayWidthSum, wasWrapped, forceRedraw, lbg)
 		} else {
 			t.markOtherLine(actualLineNum)
 		}

test/test_core.rb

@@ -1190,6 +1190,17 @@ class TestCore < TestInteractive
     tmux.until { |lines| assert lines.any_include?('9999␊10000') }
   end
 
+  def test_freeze_left_keep_right
+    tmux.send_keys %[seq 10000 | #{FZF} --read0 --delimiter "\n" --freeze-left 3 --keep-right --ellipsis XX --no-multi-line --bind space:toggle-multi-line], :Enter
+    tmux.until { |lines| assert_match(/^> 1␊2␊3XX.*10000␊$/, lines[-3]) }
+    tmux.send_keys '5'
+    tmux.until { |lines| assert_match(/^> 1␊2␊3␊4␊5␊.*XX$/, lines[-3]) }
+    tmux.send_keys :Space
+    tmux.until { |lines| assert lines.any_include?('> 1') }
+    tmux.send_keys :Space
+    tmux.until { |lines| assert lines.any_include?('1␊2␊3␊4␊5␊') }
+  end
+
   def test_backward_eof
     tmux.send_keys "echo foo | #{FZF} --bind 'backward-eof:reload(seq 100)'", :Enter
     tmux.until { |lines| lines.item_count == 1 && lines.match_count == 1 }