fix(readline): flickering on line refresh (#288)

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 ### Fixed
+- Line refresh fixes (less flicker)
 - Do more checks for a TTY
   - Panic if ENOTTY is thrown from readline
   - use `x/term` function to check if a terminal

go.mod

@@ -1,6 +1,6 @@
 module hilbish
 
-go 1.17
+go 1.18
 
 require (
 	github.com/arnodel/golua v0.0.0-20220221163911-dfcf252b6f86

readline/codes.go

@@ -76,6 +76,8 @@ const (
 	seqCursorTopLeft    = "\x1b[H"  // Clears screen and places cursor on top-left
 
 	seqGetCursorPos = "\x1b6n" // response: "\x1b{Line};{Column}R"
+	seqHideCursor = "\x1b[?25l"
+	seqUnhideCursor = "\x1b[?25h"
 
 	seqCtrlLeftArrow  = "\x1b[1;5D"
 	seqCtrlRightArrow = "\x1b[1;5C"

readline/cursor.go

@@ -1,6 +1,7 @@
 package readline
 
 import (
+//	"fmt"
 	"os"
 	"regexp"
 	"strconv"
@@ -68,6 +69,40 @@ func (rl *Instance) getCursorPos() (x int, y int) {
 // This means that they are not used to keep any reference point when
 // when we internally move around clearning and printing things
 
+/*
+func moveCursorUpBuffered(i int) {
+	if i < 1 {
+		return
+	}
+
+	fmt.Fprintf(rl.bufferedOut, "\x1b[%dA", i)
+}
+
+func moveCursorDownBuffered(i int) {
+	if i < 1 {
+		return
+	}
+
+	fmt.Fprintf(rl.bufferedOut, "\x1b[%dB", i)
+}
+
+func moveCursorForwardsBuffered(i int) {
+	if i < 1 {
+		return
+	}
+
+	fmt.Fprintf(rl.bufferedOut, "\x1b[%dC", i)
+}
+
+func moveCursorUpBuffered(i int) {
+	if i < 1 {
+		return
+	}
+
+	fmt.Fprintf(rl.bufferedOut, "\x1b[%dD", i)
+}
+*/
+
 func moveCursorUp(i int) {
 	if i < 1 {
 		return
@@ -100,6 +135,14 @@ func moveCursorBackwards(i int) {
 	printf("\x1b[%dD", i)
 }
 
+func hideCursor() {
+	print(seqHideCursor)
+}
+
+func unhideCursor() {
+	print(seqUnhideCursor)
+}
+
 func (rl *Instance) backspace(forward bool) {
 	if len(rl.line) == 0 || rl.pos == 0 {
 		return

readline/go.mod

@@ -1,6 +1,6 @@
 module github.com/maxlandon/readline
 
-go 1.16
+go 1.18
 
 require (
 	github.com/acarl005/stripansi v0.0.0-20180116102854-5a71ef0e047d

readline/instance.go

@@ -1,6 +1,7 @@
 package readline
 
 import (
+	"bufio"
 	"os"
 	"regexp"
 	"sync"
@@ -203,6 +204,8 @@ type Instance struct {
 	ViActionCallback func(ViAction, []string)
 
 	RawInputCallback func([]rune) // called on all input
+
+	bufferedOut *bufio.Writer
 }
 
 // NewInstance is used to create a readline instance and initialise it with sane defaults.
@@ -251,6 +254,8 @@ func NewInstance() *Instance {
 		return suggs
 	}
 
+	rl.bufferedOut = bufio.NewWriter(os.Stdout)
+
 	// Registers
 	rl.initRegisters()
 

readline/line.go

@@ -33,19 +33,20 @@ func (rl *Instance) GetLine() []rune {
 func (rl *Instance) echo() {
 
 	// Then we print the prompt, and the line,
+	hideCursor()
 	switch {
 	case rl.PasswordMask != 0:
 	case rl.PasswordMask > 0:
-		print(strings.Repeat(string(rl.PasswordMask), len(rl.line)) + " ")
+		rl.bufprint(strings.Repeat(string(rl.PasswordMask), len(rl.line)) + " ")
 
 	default:
+
 		// Go back to prompt position, and clear everything below
 		moveCursorBackwards(GetTermWidth())
 		moveCursorUp(rl.posY)
-		print(seqClearScreenBelow)
 
 		// Print the prompt
-		print(string(rl.realPrompt))
+		rl.bufprint(string(rl.realPrompt))
 
 		// Assemble the line, taking virtual completions into account
 		var line []rune
@@ -57,11 +58,14 @@ func (rl *Instance) echo() {
 
 		// Print the input line with optional syntax highlighting
 		if rl.SyntaxHighlighter != nil {
-			print(rl.SyntaxHighlighter(line))
+			rl.bufprint(rl.SyntaxHighlighter(line))
 		} else {
-			print(string(line))
+			rl.bufprint(string(line))
 		}
+		rl.bufprint(seqClearScreenBelow)
+
 	}
+	rl.bufflush()
 
 	// Update references with new coordinates only now, because
 	// the new line may be longer/shorter than the previous one.
@@ -72,6 +76,7 @@ func (rl *Instance) echo() {
 	moveCursorUp(rl.fullY)
 	moveCursorDown(rl.posY)
 	moveCursorForwards(rl.posX)
+	unhideCursor()
 }
 
 func (rl *Instance) insert(r []rune) {
@@ -159,7 +164,7 @@ func (rl *Instance) clearLine() {
 	moveCursorForwards(rl.promptLen)
 
 	// Clear everything after & below the cursor
-	print(seqClearScreenBelow)
+	//print(seqClearScreenBelow)
 
 	// Real input line
 	rl.line = []rune{}

readline/prompt.go

@@ -48,7 +48,7 @@ func (rl *Instance) RefreshPromptLog(log string) (err error) {
 	rl.stillOnRefresh = true
 	moveCursorUp(rl.infoY + rl.tcUsedY)
 	moveCursorBackwards(GetTermWidth())
-	print("\r\n" + seqClearScreenBelow)
+	//print("\r\n" + seqClearScreenBelow)
 
 	// Print the log
 	fmt.Printf(log)
@@ -97,7 +97,7 @@ func (rl *Instance) RefreshPromptInPlace(prompt string) (err error) {
 	print(seqClearLine)
 	moveCursorUp(rl.infoY + rl.tcUsedY)
 	moveCursorBackwards(GetTermWidth())
-	print("\r\n" + seqClearScreenBelow)
+	//print("\r\n" + seqClearScreenBelow)
 
 	// Add a new line if needed
 	if rl.Multiline {
@@ -137,7 +137,7 @@ func (rl *Instance) RefreshPromptCustom(prompt string, offset int, clearLine boo
 	moveCursorUp(offset)
 
 	// Then clear everything below our new position
-	print(seqClearScreenBelow)
+	//print(seqClearScreenBelow)
 
 	// Update the prompt if a special has been passed.
 	if prompt != "" {

readline/tab.go

@@ -276,13 +276,14 @@ func (rl *Instance) writeTabCompletion() {
 	// than what their MaxLength allows them to, cycling sometimes occur,
 	// but does not fully clears itself: some descriptions are messed up with.
 	// We always clear the screen as a result, between writings.
-	print(seqClearScreenBelow)
+	//rl.bufprint(seqClearScreenBelow)
 
 	// Crop the completions so that it fits within our MaxTabCompleterRows
 	completions, rl.tcUsedY = rl.cropCompletions(completions)
 
 	// Then we print all of them.
-	fmt.Printf(completions)
+	rl.bufprintF(completions)
+	rl.bufflush()
 }
 
 // cropCompletions - When the user cycles through a completion list longer

readline/update.go

@@ -1,6 +1,7 @@
 package readline
 
 import (
+	"fmt"
 	"strings"
 
 	"golang.org/x/text/width"
@@ -10,7 +11,7 @@ import (
 // it should coordinate reprinting the input line, any Infos and completions
 // and manage to get back to the current (computed) cursor coordinates
 func (rl *Instance) updateHelpers() {
-
+	print(seqHideCursor)
 	// Load all Infos & completions before anything.
 	// Thus overwrites anything having been dirtily added/forced/modified, like rl.SetInfoText()
 	rl.getInfoText()
@@ -27,6 +28,7 @@ func (rl *Instance) updateHelpers() {
 	// We are at the prompt line (with the latter
 	// not printed yet), then reprint everything
 	rl.renderHelpers()
+	print(seqUnhideCursor)
 }
 
 const tabWidth = 4
@@ -119,7 +121,7 @@ func (rl *Instance) clearHelpers() {
 	moveCursorForwards(rl.fullX)
 
 	// Clear everything below
-	print(seqClearScreenBelow)
+	//print(seqClearScreenBelow)
 
 	// Go back to current cursor position
 	moveCursorBackwards(GetTermWidth())
@@ -194,3 +196,15 @@ func (rl *Instance) renderHelpers() {
 	moveCursorUp(rl.fullY - rl.posY)
 	moveCursorForwards(rl.posX)
 }
+
+func (rl *Instance) bufprintF(format string, a ...any) {
+	fmt.Fprintf(rl.bufferedOut, format, a...)
+}
+
+func (rl *Instance) bufprint(text string) {
+	fmt.Fprint(rl.bufferedOut, text)
+}
+
+func (rl *Instance) bufflush() {
+	rl.bufferedOut.Flush()
+}