Adding showchars option

internal/config/settings.go

@@ -70,7 +70,7 @@ var defaultCommonSettings = map[string]interface{}{
 	"hltrailingws":    false,
 	"ignorecase":      true,
 	"incsearch":       true,
-	"indentchar":      " ",
+	"indentchar":      " ", // Deprecated
 	"keepautoindent":  false,
 	"matchbrace":      true,
 	"matchbraceleft":  true,
@@ -88,6 +88,7 @@ var defaultCommonSettings = map[string]interface{}{
 	"scrollbar":       false,
 	"scrollmargin":    float64(3),
 	"scrollspeed":     float64(2),
+	"showchars":       "",
 	"smartpaste":      true,
 	"softwrap":        false,
 	"splitbottom":     true,
@@ -210,6 +211,7 @@ func validateParsedSettings() error {
 			}
 			continue
 		}
+
 		if _, ok := defaults[k]; ok {
 			if e := verifySetting(k, v, defaults[k]); e != nil {
 				err = e

internal/display/bufwindow.go

@@ -2,6 +2,7 @@ package display
 
 import (
 	"strconv"
+	"strings"
 
 	runewidth "github.com/mattn/go-runewidth"
 	"github.com/micro-editor/tcell/v2"
@@ -450,6 +451,30 @@ func (w *BufWindow) displayBuffer() {
 	cursors := b.GetCursors()
 
 	curStyle := config.DefStyle
+
+	// Parse showchars which is in the format of key1=val1,key2=val2,...
+	spacechars := " "
+	tabchars := b.Settings["indentchar"].(string)
+	var indentspacechars string
+	var indenttabchars string
+	for _, entry := range strings.Split(b.Settings["showchars"].(string), ",") {
+		split := strings.SplitN(entry, "=", 2)
+		if len(split) < 2 {
+			continue
+		}
+		key, val := split[0], split[1]
+		switch key {
+		case "space":
+			spacechars = val
+		case "tab":
+			tabchars = val
+		case "ispace":
+			indentspacechars = val
+		case "itab":
+			indenttabchars = val
+		}
+	}
+
 	for ; vloc.Y < w.bufHeight; vloc.Y++ {
 		vloc.X = 0
 
@@ -495,7 +520,7 @@ func (w *BufWindow) displayBuffer() {
 		bloc.X = bslice
 
 		// returns the rune to be drawn, style of it and if the bg should be preserved
-		getRuneStyle := func(r rune, style tcell.Style, isplaceholder bool) (rune, tcell.Style, bool) {
+		getRuneStyle := func(r rune, style tcell.Style, showoffset int, linex int, isplaceholder bool) (rune, tcell.Style, bool) {
 			if nColsBeforeStart > 0 || vloc.Y < 0 || isplaceholder {
 				return r, style, false
 			}
@@ -518,19 +543,33 @@ func (w *BufWindow) displayBuffer() {
 				return r, style, false
 			}
 
-			var drawrune rune
-			if r == '\t' {
-				indentrunes := []rune(b.Settings["indentchar"].(string))
-				// if empty indentchar settings, use space
-				if len(indentrunes) == 0 {
-					indentrunes = []rune{' '}
+			var indentrunes []rune
+			switch r {
+			case '\t':
+				if bloc.X < leadingwsEnd && indenttabchars != "" {
+					indentrunes = []rune(indenttabchars)
+				} else {
+					indentrunes = []rune(tabchars)
 				}
+			case ' ':
+				if linex%tabsize == 0 && bloc.X < leadingwsEnd && indentspacechars != "" {
+					indentrunes = []rune(indentspacechars)
+				} else {
+					indentrunes = []rune(spacechars)
+				}
+			}
 
-				drawrune = indentrunes[0]
-				if s, ok := config.Colorscheme["indent-char"]; ok {
-					fg, _, _ := s.Decompose()
-					style = style.Foreground(fg)
-				}
+			var drawrune rune
+			if showoffset < len(indentrunes) {
+				drawrune = indentrunes[showoffset]
+			} else {
+				// use space if no showchars or after we showed showchars
+				drawrune = ' '
+			}
+
+			if s, ok := config.Colorscheme["indent-char"]; ok {
+				fg, _, _ := s.Decompose()
+				style = style.Foreground(fg)
 			}
 
 			preservebg := false
@@ -692,6 +731,7 @@ func (w *BufWindow) displayBuffer() {
 
 			width := 0
 
+			linex := totalwidth
 			switch r {
 			case '\t':
 				ts := tabsize - (totalwidth % tabsize)
@@ -732,15 +772,15 @@ func (w *BufWindow) displayBuffer() {
 			}
 
 			for _, r := range word {
-				drawrune, drawstyle, preservebg := getRuneStyle(r.r, r.style, false)
+				drawrune, drawstyle, preservebg := getRuneStyle(r.r, r.style, 0, linex, false)
 				draw(drawrune, r.combc, drawstyle, true, true, preservebg)
 
 				// Draw extra characters for tabs or wide runes
 				for i := 1; i < r.width; i++ {
 					if r.r == '\t' {
-						drawrune, drawstyle, preservebg = getRuneStyle('\t', r.style, false)
+						drawrune, drawstyle, preservebg = getRuneStyle('\t', r.style, i, linex+i, false)
 					} else {
-						drawrune, drawstyle, preservebg = getRuneStyle(' ', r.style, true)
+						drawrune, drawstyle, preservebg = getRuneStyle(' ', r.style, i, linex+i, true)
 					}
 					draw(drawrune, nil, drawstyle, true, false, preservebg)
 				}
@@ -787,7 +827,7 @@ func (w *BufWindow) displayBuffer() {
 
 		if vloc.X != maxWidth {
 			// Display newline within a selection
-			drawrune, drawstyle, preservebg := getRuneStyle(' ', config.DefStyle, true)
+			drawrune, drawstyle, preservebg := getRuneStyle(' ', config.DefStyle, 0, totalwidth, true)
 			draw(drawrune, nil, drawstyle, true, true, preservebg)
 		}
 

runtime/help/options.md

@@ -203,12 +203,8 @@ Here are the available options:
 
     default value: `true`
 
-* `indentchar`: sets the indentation character. This will not be inserted into
-   files; it is only a visual indicator that whitespace is present. If set to a
-   printing character, it functions as a subset of the "show invisibles"
-   setting available in many other text editors. The color of this character is
-   determined by the `indent-char` field in the current theme rather than the
-   default text color.
+* `indentchar`: sets the character to be shown to display tab characters.
+   This option is **deprecated**, use the `tab` key in `showchars` option instead.
 
     default value: ` ` (space)
 
@@ -386,6 +382,25 @@ Here are the available options:
 
     default value: `2`
 
+* `showchars`: sets what characters to be shown to display various invisible
+   characters in the file. The characters shown will not be inserted into files.
+   This option is specified in the form of `key1=value1,key2=value2,...`.
+
+   Here are the list of keys:
+   - `space`: space characters
+   - `tab`: tab characters. If set, overrides the `indentchar` option.
+   - `ispace`: space characters at indent position before the first visible
+               character in a line. If this is not set, `space` will be shown
+               instead.
+   - `itab`: tab characters before the first visible character in a line.
+             If this is not set, `tab` will be shown instead.
+   An example of this option value could be `tab=>,space=.,itab=|>,ispace=|`
+
+   The color of the shown character is determined by the `indent-char`
+   field in the current theme rather than the default text color.
+
+    default value: ``
+
 * `smartpaste`: add leading whitespace when pasting multiple lines.
    This will attempt to preserve the current indentation level when pasting an
    unindented block.
@@ -577,6 +592,7 @@ so that you can see what the formatting should look like.
     "scrollbarchar": "|",
     "scrollmargin": 3,
     "scrollspeed": 2,
+    "showchars": "",
     "smartpaste": true,
     "softwrap": false,
     "splitbottom": true,