Merge branch 'johan/scroll-hints'

Fixes #94.

m/ansiTokenizer.go

@@ -30,8 +30,8 @@ type Line struct {
 }
 
 // NewLine creates a new Line from a (potentially ANSI / man page formatted) string
-func NewLine(raw string) *Line {
-	return &Line{
+func NewLine(raw string) Line {
+	return Line{
 		raw:   raw,
 		plain: nil,
 	}

m/pager.go

@@ -69,6 +69,10 @@ type Pager struct {
 
 	WrapLongLines bool
 
+	// Ref: https://github.com/walles/moar/issues/94
+	ScrollLeftHint  twin.Cell
+	ScrollRightHint twin.Cell
+
 	// If true, pager will clear the screen on return. If false, pager will
 	// clear the last line, and show the cursor.
 	DeInit bool
@@ -143,6 +147,8 @@ func NewPager(r *Reader) *Pager {
 		ShowLineNumbers: true,
 		ShowStatusBar:   true,
 		DeInit:          true,
+		ScrollLeftHint:  twin.NewCell('<', twin.StyleDefault.WithAttr(twin.AttrReverse)),
+		ScrollRightHint: twin.NewCell('>', twin.StyleDefault.WithAttr(twin.AttrReverse)),
 		scrollPosition:  newScrollPosition(name),
 	}
 }

m/reader.go

@@ -191,7 +191,7 @@ func (reader *Reader) readStream(stream io.Reader, originalFileName *string, fro
 			reader.lock.Unlock()
 			break
 		}
-		reader.lines = append(reader.lines, newLine)
+		reader.lines = append(reader.lines, &newLine)
 		reader.lock.Unlock()
 		completeLine = completeLine[:0]
 
@@ -263,8 +263,9 @@ func NewReaderFromText(name string, text string) *Reader {
 	noExternalNewlines := strings.Trim(text, "\n")
 	lines := []*Line{}
 	if len(noExternalNewlines) > 0 {
-		for _, line := range strings.Split(noExternalNewlines, "\n") {
-			lines = append(lines, NewLine(line))
+		for _, lineString := range strings.Split(noExternalNewlines, "\n") {
+			line := NewLine(lineString)
+			lines = append(lines, &line)
 		}
 	}
 	done := make(chan bool, 1)
@@ -540,8 +541,9 @@ func (r *Reader) getLinesUnlocked(firstLineOneBased int, wantedLineCount int) *I
 // Replace reader contents with the given text and mark as done
 func (reader *Reader) setText(text string) {
 	lines := []*Line{}
-	for _, line := range strings.Split(text, "\n") {
-		lines = append(lines, NewLine(line))
+	for _, lineString := range strings.Split(text, "\n") {
+		line := NewLine(lineString)
+		lines = append(lines, &line)
 	}
 
 	if len(lines) > 0 && strings.HasSuffix(text, "\n") {

m/screenLines.go

@@ -211,18 +211,12 @@ func (p *Pager) decorateLine(lineNumberToShow *int, contents []twin.Cell) []twin
 		}
 
 		// Add can-scroll-left marker
-		newLine[0] = twin.Cell{
-			Rune:  '<',
-			Style: twin.StyleDefault.WithAttr(twin.AttrReverse),
-		}
+		newLine[0] = p.ScrollLeftHint
 	}
 
 	// Add scroll right indicator
 	if len(contents)+numberPrefixLength-p.leftColumnZeroBased > width {
-		newLine[width-1] = twin.Cell{
-			Rune:  '>',
-			Style: twin.StyleDefault.WithAttr(twin.AttrReverse),
-		}
+		newLine[width-1] = p.ScrollRightHint
 	}
 
 	return newLine

m/screenLines_test.go

@@ -9,13 +9,15 @@ import (
 )
 
 func testHorizontalCropping(t *testing.T, contents string, firstIndex int, lastIndex int, expected string) {
-	pager := Pager{
-		screen:              twin.NewFakeScreen(1+lastIndex-firstIndex, 99),
-		leftColumnZeroBased: firstIndex,
-		scrollPosition:      newScrollPosition("testHorizontalCropping"),
-	}
+	pager := NewPager(nil)
+	pager.ShowLineNumbers = false
+
+	pager.screen = twin.NewFakeScreen(1+lastIndex-firstIndex, 99)
+	pager.leftColumnZeroBased = firstIndex
+	pager.scrollPosition = newScrollPosition("testHorizontalCropping")
+
 	lineContents := NewLine(contents)
-	screenLine := pager.renderLine(lineContents, 0)
+	screenLine := pager.renderLine(&lineContents, 0)
 	assert.Equal(t, rowToString(screenLine[0].cells), expected)
 }
 

moar.1

@@ -51,6 +51,24 @@ Hide the status bar, toggle with
 \fB\-\-render\-unprintable\fR={\fBhighlight\fR | \fBwhitespace\fR}
 How unprintable characters are rendered
 .TP
+\fB\-\-scroll\-left\-hint\fR=string
+UTF-8 character indicating the view can scroll left, defaults to an inverse \fB<\fR.
+This can be a string containing ANSI formatting.
+The word
+.B ESC
+in caps will be interpreted as one escape character.
+Example value for faint (using ANSI SGR code 2) tilde characters:
+.B ESC[2m~
+.TP
+\fB\-\-scroll\-right\-hint\fR=string
+UTF-8 character indicating the view can scroll right, defaults to an inverse \fB>\fR.
+This can be a string containing ANSI formatting.
+The word
+.B ESC
+in caps will be interpreted as one escape character.
+Example value for faint (using ANSI SGR code 2) tilde characters:
+.B ESC[2m~
+.TP
 \fB\-\-statusbar\fR={\fBinverse\fR | \fBplain\fR | \fBbold\fR}
 Status bar style
 .TP

moar.go

@@ -216,6 +216,23 @@ func parseUnprintableStyle(styleOption string, flagSet *flag.FlagSet) m.Unprinta
 	panic("os.Exit(1) just failed")
 }
 
+func parseScrollHint(scrollHint string, flagSet *flag.FlagSet) twin.Cell {
+	scrollHint = strings.ReplaceAll(scrollHint, "ESC", "\x1b")
+	hintParser := m.NewLine(scrollHint)
+	parsedTokens := hintParser.HighlightedTokens(nil)
+	if len(parsedTokens) == 1 {
+		return parsedTokens[0]
+	}
+
+	fmt.Fprintln(os.Stderr,
+		"ERROR: Scroll hint must be exactly one (optionally highlighted) character. For example: 'ESC[2m…'")
+	fmt.Fprintln(os.Stderr)
+	printUsage(os.Stderr, flagSet, true)
+
+	os.Exit(1)
+	panic("os.Exit(1) just failed")
+}
+
 func main() {
 	// FIXME: If we get a CTRL-C, get terminal back into a useful state before terminating
 
@@ -244,7 +261,12 @@ func main() {
 	noStatusBar := flagSet.Bool("no-statusbar", false, "Hide the status bar, toggle with '='")
 	noClearOnExit := flagSet.Bool("no-clear-on-exit", false, "Retain screen contents when exiting moar")
 	statusBarStyleOption := flagSet.String("statusbar", "inverse", "Status bar style: inverse, plain or bold")
-	UnprintableStyleOption := flagSet.String("render-unprintable", "highlight", "How unprintable characters are rendered: highlight or whitespace")
+	UnprintableStyleOption := flagSet.String("render-unprintable", "highlight",
+		"How unprintable characters are rendered: highlight or whitespace")
+	scrollLeftHintOption := flagSet.String("scroll-left-hint", "ESC[7m<",
+		"Shown when view can scroll left. One character with optional ANSI highlighting.")
+	scrollRightHintOption := flagSet.String("scroll-right-hint", "ESC[7m>",
+		"Shown when view can scroll right. One character with optional ANSI highlighting.")
 
 	// Combine flags from environment and from command line
 	flags := os.Args[1:]
@@ -275,6 +297,9 @@ func main() {
 	statusBarStyle := parseStatusBarStyle(*statusBarStyleOption, flagSet)
 	unprintableStyle := parseUnprintableStyle(*UnprintableStyleOption, flagSet)
 
+	scrollLeftHint := parseScrollHint(*scrollLeftHintOption, flagSet)
+	scrollRightHint := parseScrollHint(*scrollRightHintOption, flagSet)
+
 	log.SetLevel(log.InfoLevel)
 	if *trace {
 		log.SetLevel(log.TraceLevel)
@@ -343,7 +368,9 @@ func main() {
 	if stdinIsRedirected {
 		// Display input pipe contents
 		reader := m.NewReaderFromStream("", os.Stdin)
-		startPaging(reader, *wrap, *noLineNumbers, *noStatusBar, *noClearOnExit, statusBarStyle, unprintableStyle)
+		startPaging(reader,
+			*wrap, *noLineNumbers, *noStatusBar, *noClearOnExit, statusBarStyle, unprintableStyle,
+			scrollLeftHint, scrollRightHint)
 		return
 	}
 
@@ -353,13 +380,17 @@ func main() {
 		fmt.Fprintf(os.Stderr, "ERROR: %v\n", err)
 		os.Exit(1)
 	}
-	startPaging(reader, *wrap, *noLineNumbers, *noStatusBar, *noClearOnExit, statusBarStyle, unprintableStyle)
+	startPaging(reader,
+		*wrap, *noLineNumbers, *noStatusBar, *noClearOnExit, statusBarStyle, unprintableStyle,
+		scrollLeftHint, scrollRightHint)
 }
 
 func startPaging(reader *m.Reader,
 	wrapLongLines, noLineNumbers, noStatusBar, noClearOnExit bool,
 	statusBarStyle m.StatusBarStyle,
 	unprintableStyle m.UnprintableStyle,
+	scrollLeftHint twin.Cell,
+	scrollRightHint twin.Cell,
 ) {
 	screen, e := twin.NewScreen()
 	if e != nil {
@@ -374,6 +405,8 @@ func startPaging(reader *m.Reader,
 	pager.ShowStatusBar = !noStatusBar
 	pager.StatusBarStyle = statusBarStyle
 	pager.UnprintableStyle = unprintableStyle
+	pager.ScrollLeftHint = scrollLeftHint
+	pager.ScrollRightHint = scrollRightHint
 
 	defer func() {
 		// Restore screen...

moar_test.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/walles/moar/twin"
+	"gotest.tools/assert"
+)
+
+func TestParseScrollHint(t *testing.T) {
+	token := parseScrollHint("ESC[7m>", nil)
+	assert.Equal(t, token, twin.Cell{
+		Rune:  '>',
+		Style: twin.StyleDefault.WithAttr(twin.AttrReverse),
+	})
+}