Merge pull request #17589 from kchibisov/add-dashed-dotted-underline

Add support for double, dashed, and dotted underlines 

3 files changed, 36 insertions, 20 deletions

diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 03a5f98c6d..b0859d1cea 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -7937,8 +7937,11 @@ synIDattr({synID}, {what} [, {mode}])			*synIDattr()*
 		"inverse"	"1" if inverse (= reverse)
 		"standout"	"1" if standout
 		"underline"	"1" if underlined
+		"underlineline"	"1" if double underlined
 		"undercurl"	"1" if undercurled
-		"strikethrough"	"1" if struckthrough
+		"underdot"	"1" if dotted underlined
+		"underdash"	"1" if dashed underlined
+		"strikethrough" "1" if struckthrough
 
 		Example (echoes the color of the syntax item under the
 		cursor): >
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 778f829a4e..9084c5315a 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -4875,7 +4875,8 @@ the same syntax file on all UIs.
 
 1. TUI highlight arguments
 
-					*bold* *underline* *undercurl*
+					*bold* *underline* *underlineline*
+					*undercurl* *underdot* *underdash*
 					*inverse* *italic* *standout*
 					*nocombine* *strikethrough*
 cterm={attr-list}			*attr-list* *highlight-cterm* *E418*
@@ -4883,7 +4884,10 @@ cterm={attr-list}			*attr-list* *highlight-cterm* *E418*
 	following items (in any order):
 		bold
 		underline
+		underlineline	double underline
 		undercurl	curly underline
+		underdot	dotted underline
+		underdash	dashed underline
 		strikethrough
 		reverse
 		inverse		same as reverse
@@ -4894,8 +4898,9 @@ cterm={attr-list}			*attr-list* *highlight-cterm* *E418*
 
 	Note that "bold" can be used here and by using a bold font.  They
 	have the same effect.
-	"undercurl" falls back to "underline" in a terminal that does not
-	support it.  The color is set using |highlight-guisp|.
+	"underlineline", "undercurl", "underdot", and "underdash" fall back
+	to "underline" in a terminal that does not support them. The color is
+	set using |highlight-guisp|.
 
 start={term-list}				*highlight-start* *E422*
 stop={term-list}				*term-list* *highlight-stop*
@@ -5028,8 +5033,8 @@ guifg={color-name}					*highlight-guifg*
 guibg={color-name}					*highlight-guibg*
 guisp={color-name}					*highlight-guisp*
 	These give the foreground (guifg), background (guibg) and special
-	(guisp) color to use in the GUI.  "guisp" is used for undercurl
-	and underline.
+	(guisp) color to use in the GUI.  "guisp" is used for various
+	underlines.
 	There are a few special names:
 		NONE		no color (transparent)
 		bg		use normal background color
diff --git a/runtime/doc/ui.txt b/runtime/doc/ui.txt
index e7be14e732..c5e3b60079 100644
--- a/runtime/doc/ui.txt
+++ b/runtime/doc/ui.txt
@@ -283,19 +283,24 @@ numerical highlight ids to the actual attributes.
 	attributes specified by the `rgb_attr` and `cterm_attr` dicts, with the
 	following (all optional) keys.
 
-	`foreground`:	foreground color.
-	`background`:	background color.
-	`special`:	color to use for underline and undercurl, when present.
-	`reverse`:	reverse video. Foreground and background colors are
-			switched.
-	`italic`:	italic text.
-	`bold`:		bold text.
-	`strikethrough`:  struckthrough text.
-	`underline`:	underlined text. The line has `special` color.
-	`undercurl`:	undercurled text. The curl has `special` color.
-	`blend`:	Blend level (0-100). Could be used by UIs to support
-			blending floating windows to the background or to
-			signal a transparent cursor.
+	`foreground`:		foreground color.
+	`background`:		background color.
+	`special`:		color to use for various underlines, when
+				present.
+	`reverse`:		reverse video. Foreground and background colors
+				are switched.
+	`italic`:		italic text.
+	`bold`:			bold text.
+	`strikethrough`:	struckthrough text.
+	`underline`:		underlined text. The line has `special` color.
+	`underlineline`:	double underlined text. The lines have `special`
+				color.
+	`undercurl`:		undercurled text. The curl has `special` color.
+	`underdot`:		underdotted text. The dots have `special` color.
+	`underdash`:		underdashed text. The dashes have `special` color.
+	`blend`:		Blend level (0-100). Could be used by UIs to
+				support blending floating windows to the
+				background or to signal a transparent cursor.
 
 	For absent color keys the default color should be used. Don't store
 	the default value in the table, rather a sentinel value, so that
@@ -444,14 +449,17 @@ is not active. New UIs should implement |ui-linegrid| instead.
 
 	`foreground`:	foreground color.
 	`background`:	background color.
-	`special`:	color to use for underline and undercurl, when present.
+	`special`:	color to use for various underlines, when present.
 	`reverse`:	reverse video. Foreground and background colors are
 			switched.
 	`italic`:	italic text.
 	`bold`:		bold text.
 	`strikethrough`:  struckthrough text.
 	`underline`:	underlined text. The line has `special` color.
+	`underlineline`:  double underlined text. The lines have `special` color.
 	`undercurl`:	undercurled text. The curl has `special` color.
+	`underdot`:	underdotted text. The dots have `special` color.
+	`underdash`:	underdashed text. The dashes have `special` color.
 
 ["put", text]
 	The (utf-8 encoded) string `text` is put at the cursor position