Add support vertical header and header column

Add command line options for vertical header and vertical header column.
The specified vertical header will be displayed fixedly.
Only one of vertical header or vertical header column can be applied.

main.go

@@ -438,6 +438,17 @@ func init() {
 		return []string{"1"}, cobra.ShellCompDirectiveNoFileComp
 	})
 
+	rootCmd.PersistentFlags().IntP("vertical-header", "y", 0, "number of characters to display as a vertical header")
+	_ = viper.BindPFlag("general.VerticalHeader", rootCmd.PersistentFlags().Lookup("vertical-header"))
+	_ = rootCmd.RegisterFlagCompletionFunc("vertical-header", func(_ *cobra.Command, _ []string, _ string) ([]string, cobra.ShellCompDirective) {
+		return []string{"1"}, cobra.ShellCompDirectiveNoFileComp
+	})
+	rootCmd.PersistentFlags().IntP("header-column", "Y", 0, "number of columns to display as a vertical header")
+	_ = viper.BindPFlag("general.VerticalHeaderColumn", rootCmd.PersistentFlags().Lookup("header-column"))
+	_ = rootCmd.RegisterFlagCompletionFunc("header-column", func(_ *cobra.Command, _ []string, _ string) ([]string, cobra.ShellCompDirective) {
+		return []string{"1"}, cobra.ShellCompDirectiveNoFileComp
+	})
+
 	rootCmd.PersistentFlags().IntP("skip-lines", "", 0, "skip the number of lines")
 	_ = viper.BindPFlag("general.SkipLines", rootCmd.PersistentFlags().Lookup("skip-lines"))
 	_ = rootCmd.RegisterFlagCompletionFunc("skip-lines", func(_ *cobra.Command, _ []string, _ string) ([]string, cobra.ShellCompDirective) {

oviewer/config.go

@@ -33,6 +33,8 @@ type Config struct {
 	StyleMarkLine OVStyle
 	// StyleSectionLine is a style that section delimiter line.
 	StyleSectionLine OVStyle
+	// StyleVerticalHeader is a style that applies to the vertical header.
+	StyleVerticalHeader OVStyle
 	// StyleJumpTargetLine is the line that displays the search results.
 	StyleJumpTargetLine OVStyle
 	// StyleAlternate is a style that applies line by line.
@@ -108,12 +110,10 @@ func NewConfig() Config {
 			Background: "gray",
 		},
 		StyleOverStrike: OVStyle{
-			Bold:           true,
-			UnderlineStyle: "3",
+			Bold: true,
 		},
 		StyleOverLine: OVStyle{
-			Underline:      true,
-			UnderlineStyle: "2",
+			Underline: true,
 		},
 		StyleLineNumber: OVStyle{
 			Bold: true,
@@ -130,6 +130,9 @@ func NewConfig() Config {
 		StyleSectionLine: OVStyle{
 			Background: "slateblue",
 		},
+		StyleVerticalHeader: OVStyle{
+			Reverse: true,
+		},
 		StyleMultiColorHighlight: []OVStyle{
 			{Foreground: "red"},
 			{Foreground: "aqua"},

oviewer/draw.go

@@ -165,7 +165,7 @@ func (root *Root) drawWrapLine(y int, lX int, lN int, lineC LineC) (int, int) {
 		log.Printf("Illegal lX:%d", lX)
 		return 0, 0
 	}
-
+	currentLX := lX
 	screen := root.Screen
 	for n := 0; ; n++ {
 		x := root.scr.startX + n
@@ -185,7 +185,9 @@ func (root *Root) drawWrapLine(y int, lX int, lN int, lineC LineC) (int, int) {
 		}
 		screen.SetContent(x, y, c.mainc, c.combc, c.style)
 	}
-
+	if currentLX == 0 {
+		root.drawVerticalHeader(y, lineC)
+	}
 	return lX, lN
 }
 
@@ -209,10 +211,34 @@ func (root *Root) drawNoWrapLine(y int, lX int, lN int, lineC LineC) (int, int)
 		screen.SetContent(x, y, c.mainc, c.combc, c.style)
 	}
 	lN++
-
+	root.drawVerticalHeader(y, lineC)
 	return lX, lN
 }
 
+func (root *Root) drawVerticalHeader(y int, lineC LineC) int {
+	vheader := 0
+	if root.General.VerticalHeaderColumn > 0 && len(lineC.columnRanges) > root.General.VerticalHeaderColumn {
+		vheader = lineC.columnRanges[root.General.VerticalHeaderColumn-1].end + 1
+	}
+	if root.General.VerticalHeader > 0 {
+		vheader = root.General.VerticalHeader
+	}
+	if vheader == 0 {
+		return 0
+	}
+	screen := root.Screen
+	for n := 0; n < vheader; n++ {
+		x := root.scr.startX + n
+		c := DefaultContent
+		if n < len(lineC.lc) {
+			c = lineC.lc[n]
+		}
+		style := applyStyle(c.style, root.StyleVerticalHeader)
+		screen.SetContent(x, y, c.mainc, c.combc, style)
+	}
+	return vheader
+}
+
 // blankLineNumber should be blank for the line number.
 func (root *Root) blankLineNumber(y int) {
 	if !root.Doc.LineNumMode {

oviewer/oviewer.go

@@ -147,6 +147,10 @@ type general struct {
 	TabWidth int
 	// Header is number of header lines to be fixed.
 	Header int
+	// VerticalHeader is the number of vertical header lines.
+	VerticalHeader int
+	// VerticalHeaderColumn is the number of vertical header columns.
+	VerticalHeaderColumn int
 	// SkipLines is the rows to skip.
 	SkipLines int
 	// WatchInterval is the watch interval (seconds).