Is undercurl supportted?

[eeeXun]

I add set cursorparentfmt "\033[4:3m" in lfrc. But cursor is not showing.

[joelim-work]

lf doesn't directly write escape sequences to the terminal, because it uses the tcell module for drawing the UI. Instead it parses escape sequences and constructs a Style object containing the relevant settings.

lf/colors.go

Lines 101 to 164 in f04401b

	// ECMA-48 details the standard
	// TODO: should we support turning off attributes?
	// Probably because this is used for previewers too
	for i := 0; i < len(nums); i++ {
	n := nums[i]
	switch {
	case n == 0:
	st = tcell.StyleDefault
	case n == 1:
	st = st.Bold(true)
	case n == 2:
	st = st.Dim(true)
	case n == 3:
	st = st.Italic(true)
	case n == 4:
	st = st.Underline(true)
	case n == 5 || n == 6:
	st = st.Blink(true)
	case n == 7:
	st = st.Reverse(true)
	case n == 8:
	// TODO: tcell PR for proper conceal
	_, bg, _ := st.Decompose()
	st = st.Foreground(bg)
	case n == 9:
	st = st.StrikeThrough(true)
	case n >= 30 && n <= 37:
	st = st.Foreground(tcell.PaletteColor(n - 30))
	case n >= 90 && n <= 97:
	st = st.Foreground(tcell.PaletteColor(n - 82))
	case n == 38:
	if i+3 <= len(nums) && nums[i+1] == 5 {
	st = st.Foreground(tcell.PaletteColor(nums[i+2]))
	i += 2
	} else if i+5 <= len(nums) && nums[i+1] == 2 {
	st = st.Foreground(tcell.NewRGBColor(
	int32(nums[i+2]),
	int32(nums[i+3]),
	int32(nums[i+4])))
	i += 4
	} else {
	log.Printf("unknown ansi code or incorrect form: %d", n)
	}
	case n >= 40 && n <= 47:
	st = st.Background(tcell.PaletteColor(n - 40))
	case n >= 100 && n <= 107:
	st = st.Background(tcell.PaletteColor(n - 92))
	case n == 48:
	if i+3 <= len(nums) && nums[i+1] == 5 {
	st = st.Background(tcell.PaletteColor(nums[i+2]))
	i += 2
	} else if i+5 <= len(nums) && nums[i+1] == 2 {
	st = st.Background(tcell.NewRGBColor(
	int32(nums[i+2]),
	int32(nums[i+3]),
	int32(nums[i+4])))
	i += 4
	} else {
	log.Printf("unknown ansi code or incorrect form: %d", n)
	}
	default:
	log.Printf("unknown ansi code: %d", n)
	}
	}

For undercurl to work, support would have to be added to tcell, and I think it's unlikely to happen since it's not exactly standard.

[eeeXun]

Ok, I get it. Thank you for your reply.

[joelim-work]

With the release of tcell 2.8.0, this should now be supported, but the code still needs to be changed to handle the non-standard terminal escape sequences. The implementation should look something like below:

Rewrite applyAnsiCodes function to support 4:x tokens in colors.go:

Click to expand

func applyAnsiCodes(s string, st tcell.Style) tcell.Style {
	toks := strings.Split(s, ";")

	// ECMA-48 details the standard
	// TODO: should we support turning off attributes?
	//    Probably because this is used for previewers too
	tokslen := len(toks)
	for i := 0; i < tokslen; i++ {
		switch toks[i] {
		case "", "0":
			st = tcell.StyleDefault
		case "1":
			st = st.Bold(true)
		case "2":
			st = st.Dim(true)
		case "3":
			st = st.Italic(true)
		case "4:0":
			st = st.Underline(false)
		case "4", "4:1":
			st = st.Underline(true)
		case "4:2":
			st = st.Underline(tcell.UnderlineStyleDouble)
		case "4:3":
			st = st.Underline(tcell.UnderlineStyleCurly)
		case "4:4":
			st = st.Underline(tcell.UnderlineStyleDotted)
		case "4:5":
			st = st.Underline(tcell.UnderlineStyleDashed)
		case "5", "6":
			st = st.Blink(true)
		case "7":
			st = st.Reverse(true)
		case "8":
			// TODO: tcell PR for proper conceal
			_, bg, _ := st.Decompose()
			st = st.Foreground(bg)
		case "9":
			st = st.StrikeThrough(true)
		case "30", "31", "32", "33", "34", "35", "36", "37":
			n, _ := strconv.Atoi(toks[i])
			st = st.Foreground(tcell.PaletteColor(n - 30))
		case "90", "91", "92", "93", "94", "95", "96", "97":
			n, _ := strconv.Atoi(toks[i])
			st = st.Foreground(tcell.PaletteColor(n - 82))
		case "38":
			if toks[i+1] == "5" && i+2 < tokslen {
				n, err := strconv.Atoi(toks[i+2])
				if err != nil {
					log.Printf("unknown ansi code: %s", toks[i+2])
					continue
				}
				st = st.Foreground(tcell.PaletteColor(n))
				i += 2
			} else if toks[i+1] == "2" && i+4 < tokslen {
				r, err := strconv.Atoi(toks[i+2])
				if err != nil {
					log.Printf("unknown ansi code: %s", toks[i+2])
					continue
				}
				g, err := strconv.Atoi(toks[i+3])
				if err != nil {
					log.Printf("unknown ansi code: %s", toks[i+3])
					continue
				}
				b, err := strconv.Atoi(toks[i+4])
				if err != nil {
					log.Printf("unknown ansi code: %s", toks[i+4])
					continue
				}
				st = st.Foreground(tcell.NewRGBColor(int32(r), int32(g), int32(b)))
				i += 4
			} else {
				log.Printf("unknown ansi code or incorrect form: %s", toks[i])
			}
		case "40", "41", "42", "43", "44", "45", "46", "47":
			n, _ := strconv.Atoi(toks[i])
			st = st.Background(tcell.PaletteColor(n - 40))
		case "100", "101", "102", "103", "104", "105", "106", "107":
			n, _ := strconv.Atoi(toks[i])
			st = st.Background(tcell.PaletteColor(n - 92))
		case "48":
			if toks[i+1] == "5" && i+2 < tokslen {
				n, err := strconv.Atoi(toks[i+2])
				if err != nil {
					log.Printf("unknown ansi code: %s", toks[i+2])
					continue
				}
				st = st.Background(tcell.PaletteColor(n))
				i += 2
			} else if toks[i+1] == "2" && i+4 < tokslen {
				r, err := strconv.Atoi(toks[i+2])
				if err != nil {
					log.Printf("unknown ansi code: %s", toks[i+2])
					continue
				}
				g, err := strconv.Atoi(toks[i+3])
				if err != nil {
					log.Printf("unknown ansi code: %s", toks[i+3])
					continue
				}
				b, err := strconv.Atoi(toks[i+4])
				if err != nil {
					log.Printf("unknown ansi code: %s", toks[i+4])
					continue
				}
				st = st.Background(tcell.NewRGBColor(int32(r), int32(g), int32(b)))
				i += 4
			} else {
				log.Printf("unknown ansi code or incorrect form: %s", toks[i])
			}
		default:
			log.Printf("unknown ansi code: %s", toks[i])
		}
	}

	return st
}

Additional test cases in colors_test.go:

{"4:0", none, none},
{"4:0", none.Underline(true), none},
{"4:1", none, none.Underline(true)},
{"4:2", none, none.Underline(tcell.UnderlineStyleDouble)},
{"4:3", none, none.Underline(tcell.UnderlineStyleCurly)},
{"4:4", none, none.Underline(tcell.UnderlineStyleDotted)},
{"4:5", none, none.Underline(tcell.UnderlineStyleDashed)},

Example lfrc config for demo:

cmd test &{{
    lf -remote "send $id set cursorpreviewfmt \"\033[4:0m\""
    sleep 1
    lf -remote "send $id set cursorpreviewfmt \"\033[4:1m\""
    sleep 1
    lf -remote "send $id set cursorpreviewfmt \"\033[4:2m\""
    sleep 1
    lf -remote "send $id set cursorpreviewfmt \"\033[4:3m\""
    sleep 1
    lf -remote "send $id set cursorpreviewfmt \"\033[4:4m\""
    sleep 1
    lf -remote "send $id set cursorpreviewfmt \"\033[4:5m\""
    sleep 1
    lf -remote "send $id set cursorpreviewfmt \"\033[4m\""
}}

---

That being said, I'm not sure how much interest there is in this kind of feature so I plan to leave it here for now.

[eeeXun]

I want this feature 👀 That would be great if this feature could be implemented

[joelim-work]

Can you try #1896 to see if the patch works for you?

[eeeXun]

Yes, it works for me