Fix coloring of items with zero-width characters

This commit fixes incorrect coloring for items that contain zero-width
characters. It also makes ellipsis coloring consistent when text is
trimmed from either the left or the right.

Fix #4620
Close #4646

src/terminal.go

@@ -3475,20 +3475,74 @@ func (t *Terminal) displayWidthWithLimit(runes []rune, prefixWidth int, limit in
 func (t *Terminal) trimLeft(runes []rune, width int, ellipsisWidth int) ([]rune, int32) {
 	width = max(0, width)
 	var trimmed int32
-	// Assume that each rune takes at least one column on screen
-	if len(runes) > width {
-		diff := len(runes) - width
-		trimmed = int32(diff)
-		runes = runes[diff:]
+
+	str := string(runes)
+	runningSum := 0
+	runningSumAdjusted := 0
+	// We can't just subtract the width on each segment because there might be
+	// a tab character afterwards. For example, with the tabstop = 8:
+	//   1234____5678
+	//   234_____5678
+	//   34______5678
+	//   4_______5678
+	//   ________5678
+	//   5678
+	//   678
+	//   78
+	//   8
+	// We need to look ahead, but not to the end to avoid performance hit.
+	type queuedSegment struct {
+		rs []rune
+		w  int
+	}
+	allQueue := []queuedSegment{}
+	queuedWidth := 0
+	limit := width - ellipsisWidth
+	processQueue := func() {
+		for idx, item := range allQueue {
+			if runningSumAdjusted <= limit {
+				allQueue = allQueue[idx:]
+				return
+			}
+			runningSumAdjusted -= item.w
+			runes = runes[len(item.rs):]
+			trimmed += int32(len(item.rs))
+		}
+		allQueue = []queuedSegment{}
 	}
 
-	currentWidth := t.displayWidth(runes)
+	gr := uniseg.NewGraphemes(str)
+	queue := []queuedSegment{}
+	for gr.Next() {
+		s := gr.Str()
+		rs := gr.Runes()
 
-	for currentWidth > width-ellipsisWidth && len(runes) > 0 {
-		runes = runes[1:]
-		trimmed++
-		currentWidth = t.displayWidthWithLimit(runes, ellipsisWidth, width)
+		var w int
+		if len(rs) == 1 && rs[0] == '\t' {
+			w = t.tabstop - runningSum%t.tabstop
+		} else {
+			w = util.StringWidth(string(rs))
+		}
+		runningSum += w
+		runningSumAdjusted += w
+		queue = append(queue, queuedSegment{rs: rs, w: w})
+		queuedWidth += w
+		if queuedWidth >= t.tabstop || s == "\t" {
+			queuedWidth = 0
+
+			if s == "\t" {
+				queue[len(queue)-1].w = t.tabstop
+				for idx := range queue[:len(queue)-1] {
+					queue[idx].w = 0
+				}
+			}
+			allQueue = append(allQueue, queue...)
+			queue = []queuedSegment{}
+			processQueue()
+		}
 	}
+	allQueue = append(allQueue, queue...)
+	processQueue()
 	return runes, trimmed
 }
 
@@ -3506,9 +3560,16 @@ func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMat
 	}
 	charOffsets := matchOffsets
 	if pos != nil {
+		runes := item.text.ToRunes()
 		charOffsets = make([]Offset, len(*pos))
 		for idx, p := range *pos {
-			offset := Offset{int32(p), int32(p + 1)}
+			gr := uniseg.NewGraphemes(string(runes[p:]))
+			w := 1
+			for gr.Next() {
+				w = len(gr.Runes())
+				break
+			}
+			offset := Offset{int32(p), int32(p + w)}
 			charOffsets[idx] = offset
 		}
 		sort.Sort(ByOrder(charOffsets))
@@ -3767,24 +3828,16 @@ func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMat
 			displayWidth = t.displayWidthWithLimit(runes, 0, adjustedMaxWidth)
 			if !t.wrap && displayWidth > adjustedMaxWidth {
 				maxe = util.Constrain(maxe+min(maxWidth/2-ellipsisWidth, t.hscrollOff), 0, len(runes))
-				transformOffsets := func(diff int32, rightTrim bool) {
-					for idx, offset := range offs {
-						b, e := offset.offset[0], offset.offset[1]
-						el := int32(len(ellipsis))
-						b += el - diff
-						e += el - diff
-						b = max(b, el)
-						if rightTrim {
-							e = min(e, int32(maxWidth-ellipsisWidth))
-						}
-						offs[idx].offset[0] = b
-						offs[idx].offset[1] = max(b, e)
+				transformOffsets := func(diff int32) {
+					for idx := range offs {
+						offs[idx].offset[0] -= diff
+						offs[idx].offset[1] -= diff
 					}
 				}
 				if t.hscroll {
 					if fidx == 1 || fidx == 2 && t.keepRight && pos == nil {
 						trimmed, diff := t.trimLeft(runes, maxWidth, ellipsisWidth)
-						transformOffsets(diff, false)
+						transformOffsets(diff - int32(len(ellipsis)))
 						runes = append(ellipsis, trimmed...)
 					} else if fidx == 0 || !t.overflow(runes[:maxe], maxWidth-ellipsisWidth) {
 						// Stri..
@@ -3792,27 +3845,20 @@ func (t *Terminal) printHighlighted(result Result, colBase tui.ColorPair, colMat
 						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)
+						transformOffsets(diff - int32(len(ellipsis)))
 						runes = append(ellipsis, runes...)
 					}
 				} else {
 					runes, _ = t.trimRight(runes, maxWidth-ellipsisWidth)
 					runes = append(runes, ellipsis...)
-
-					for idx, offset := range offs {
-						offs[idx].offset[0] = min(offset.offset[0], int32(maxWidth-len(ellipsis)))
-						offs[idx].offset[1] = min(offset.offset[1], int32(maxWidth))
-					}
 				}
 				displayWidth = t.displayWidthWithLimit(runes, 0, maxWidth)
 			}

src/util/util.go

@@ -18,8 +18,13 @@ func StringWidth(s string) int {
 
 // RunesWidth returns runes width
 func RunesWidth(runes []rune, prefixWidth int, tabstop int, limit int) (int, int) {
+	return StringsWidth(string(runes), prefixWidth, tabstop, limit)
+}
+
+// StringsWidth returns the width of the string
+func StringsWidth(str string, prefixWidth int, tabstop int, limit int) (int, int) {
 	width := 0
-	gr := uniseg.NewGraphemes(string(runes))
+	gr := uniseg.NewGraphemes(str)
 	idx := 0
 	for gr.Next() {
 		rs := gr.Runes()

test/test_core.rb

@@ -2175,4 +2175,13 @@ class TestCore < TestInteractive
       assert_equal 1, it.match_count
     end
   end
+
+  def test_zero_width_characters
+    tmux.send_keys %(for i in {1..1000}; do string+="a̱$i"; printf '\\e[43m%s\\e[0m\\n' "$string"; done | #{FZF} --ansi --query a500 --ellipsis XX), :Enter
+    tmux.until do |lines|
+      assert_equal 981, lines.match_count
+      assert_match(/^> XX.*a̱500/, lines[-3])
+      assert(lines.reverse.drop(5).all? { it.match?(/^  XX.*a̱500.*XX/) })
+    end
+  end
 end