Port wcswidth to use grapheme segmentation

tools/wcswidth/wcswidth.go

@@ -12,21 +12,12 @@ import (
 
 var _ = fmt.Print
 
-func IsFlagCodepoint(ch rune) bool {
-	return 0x1F1E6 <= ch && ch <= 0x1F1FF
-}
-
-func IsFlagPair(a rune, b rune) bool {
-	return IsFlagCodepoint(a) && IsFlagCodepoint(b)
-}
-
-type ecparser_state uint8
-
 type WCWidthIterator struct {
 	prev_ch                   rune
 	prev_width, current_width int
+	seg                       GraphemeSegmentationResult
+	can_combine               bool
 	parser                    EscapeCodeParser
-	state                     ecparser_state
 	rune_count                uint
 }
 
@@ -34,6 +25,12 @@ func CreateWCWidthIterator() *WCWidthIterator {
 	var ans WCWidthIterator
 	ans.parser.HandleRune = ans.handle_rune
 	ans.parser.HandleCSI = ans.handle_csi
+	ans.parser.HandleOSC = ans.handle_st_terminated
+	ans.parser.HandleDCS = ans.handle_st_terminated
+	ans.parser.HandlePM = ans.handle_st_terminated
+	ans.parser.HandleSOS = ans.handle_st_terminated
+	ans.parser.HandleAPC = ans.handle_st_terminated
+
 	return &ans
 }
 
@@ -42,6 +39,8 @@ func (self *WCWidthIterator) Reset() {
 	self.prev_width = 0
 	self.current_width = 0
 	self.rune_count = 0
+	self.can_combine = false
+	self.seg = 0
 	self.parser.Reset()
 }
 
@@ -58,54 +57,47 @@ func (self *WCWidthIterator) handle_csi(csi []byte) error {
 			}
 		}
 	}
+	self.can_combine = false
+	self.seg = 0
+	return nil
+}
+
+func (self *WCWidthIterator) handle_st_terminated(data []byte) error {
+	self.can_combine = false
+	self.seg = 0
 	return nil
 }
 
 func (self *WCWidthIterator) handle_rune(ch rune) error {
 	self.rune_count += 1
-	const (
-		normal            ecparser_state = 0
-		flag_pair_started ecparser_state = 3
-	)
-	switch self.state {
-	case flag_pair_started:
-		self.state = normal
-		if IsFlagPair(self.prev_ch, ch) {
-			break
-		}
-		fallthrough
-	case normal:
+	cp := CharPropsFor(ch)
+	self.seg = self.seg.Step(cp)
+	if self.can_combine && self.seg.Add_to_current_cell() == 1 {
 		switch ch {
 		case 0xfe0f:
-			if IsEmojiPresentationBase(self.prev_ch) && self.prev_width == 1 {
+			if CharPropsFor(self.prev_ch).Is_emoji_presentation_base() == 1 && self.prev_width == 1 {
 				self.current_width += 1
 				self.prev_width = 2
-			} else {
-				self.prev_width = 0
 			}
 		case 0xfe0e:
-			if IsEmojiPresentationBase(self.prev_ch) && self.prev_width == 2 {
+			if CharPropsFor(self.prev_ch).Is_emoji_presentation_base() == 1 && self.prev_width == 2 {
 				self.current_width -= 1
 				self.prev_width = 1
-			} else {
-				self.prev_width = 0
 			}
-		default:
-			if IsFlagCodepoint(ch) {
-				self.state = flag_pair_started
-			}
-			w := Runewidth(ch)
-			switch w {
-			case -1:
-			case 0:
-				self.prev_width = 0
-			case 2:
-				self.prev_width = 2
-			default:
-				self.prev_width = 1
-			}
-			self.current_width += self.prev_width
 		}
+	} else {
+		width := cp.Width()
+		switch width {
+		case -1:
+		case 0:
+			self.prev_width = 0
+		case 2:
+			self.prev_width = 2
+		default:
+			self.prev_width = 1
+		}
+		self.current_width += self.prev_width
+		self.can_combine = true
 	}
 	self.prev_ch = ch
 	return nil