Clear to end of screen before redrawing prompt

multiline.go

@@ -2,8 +2,6 @@ package survey
 
 import (
 	"strings"
-
-	"github.com/AlecAivazis/survey/v2/terminal"
 )
 
 type Multiline struct {
@@ -28,12 +26,12 @@ var MultilineQuestionTemplate = `
 {{- color .Config.Icons.Question.Format }}{{ .Config.Icons.Question.Text }} {{color "reset"}}
 {{- color "default+hb"}}{{ .Message }} {{color "reset"}}
 {{- if .ShowAnswer}}
-  {{- "\n"}}{{color "cyan"}}{{.Answer}}{{color "reset"}}
-  {{- if .Answer }}{{ "\n" }}{{ end }}
+  {{- if .Answer}}{{"\n"}}{{color "cyan"}}{{.Answer}}{{color "reset"}}{{end}}
 {{- else }}
   {{- if .Default}}{{color "white"}}({{.Default}}) {{color "reset"}}{{end}}
   {{- color "cyan"}}[Enter 2 empty lines to finish]{{color "reset"}}
-{{- end}}`
+{{- end}}
+`
 
 func (i *Multiline) Prompt(config *PromptConfig) (interface{}, error) {
 	// render the template
@@ -70,13 +68,6 @@ func (i *Multiline) Prompt(config *PromptConfig) (interface{}, error) {
 
 		if string(line) == "" {
 			if emptyOnce {
-				numLines := len(multiline) + 2
-				cursor.PreviousLine(numLines)
-				for j := 0; j < numLines; j++ {
-					terminal.EraseLine(i.Stdio().Out, terminal.ERASE_LINE_ALL)
-					cursor.NextLine(1)
-				}
-				cursor.PreviousLine(numLines)
 				break
 			}
 			emptyOnce = true
@@ -86,17 +77,19 @@ func (i *Multiline) Prompt(config *PromptConfig) (interface{}, error) {
 		multiline = append(multiline, string(line))
 	}
 
-	val := strings.Join(multiline, "\n")
-	val = strings.TrimSpace(val)
+	// adjust for terminating newlines
+	cursor.PreviousLine(2)
 
-	// if the line is empty
+	// render the displayed value or use the default
+	val := strings.Join(multiline, "\n")
 	if len(val) == 0 {
-		// use the default value
 		return i.Default, err
 	}
-
 	i.AppendRenderedText(val)
-	return val, err
+
+	// remove the extra newline from the answer
+	ans := strings.TrimSuffix(val, "\n")
+	return ans, err
 }
 
 func (i *Multiline) Cleanup(config *PromptConfig, val interface{}) error {

renderer.go

@@ -42,14 +42,7 @@ func (r *Renderer) NewCursor() *terminal.Cursor {
 }
 
 func (r *Renderer) Error(config *PromptConfig, invalid error) error {
-	// cleanup the currently rendered errors
-	r.resetPrompt(r.countLines(r.renderedErrors))
-	r.renderedErrors.Reset()
-
-	// cleanup the rest of the prompt
-	r.resetPrompt(r.countLines(r.renderedText))
-	r.renderedText.Reset()
-
+	// create a formatted and plain error template with data
 	userOut, layoutOut, err := core.RunTemplate(ErrorTemplate, &ErrorTemplateData{
 		Error: invalid,
 		Icon:  config.Icons.Error,
@@ -58,7 +51,14 @@ func (r *Renderer) Error(config *PromptConfig, invalid error) error {
 		return err
 	}
 
-	// send the message to the user
+	// erase the currently rendered error and prompt
+	r.resetPrompt(r.countLines(r.renderedErrors))
+	r.renderedErrors.Reset()
+
+	r.resetPrompt(r.countLines(r.renderedText))
+	r.renderedText.Reset()
+
+	// print the formatted prompt
 	if _, err := fmt.Fprint(terminal.NewAnsiStdout(r.stdio.Out), userOut); err != nil {
 		return err
 	}
@@ -78,18 +78,17 @@ func (r *Renderer) OffsetCursor(offset int) {
 }
 
 func (r *Renderer) Render(tmpl string, data interface{}) error {
-	// cleanup the currently rendered text
-	lineCount := r.countLines(r.renderedText)
-	r.resetPrompt(lineCount)
-	r.renderedText.Reset()
-
-	// render the template summarizing the current state
+	// create a formatted and plain template with data
 	userOut, layoutOut, err := core.RunTemplate(tmpl, data)
 	if err != nil {
 		return err
 	}
 
-	// print the summary
+	// erase the currently rendered prompt
+	r.resetPrompt(r.countLines(r.renderedText))
+	r.renderedText.Reset()
+
+	// print the formatted prompt
 	if _, err := fmt.Fprint(terminal.NewAnsiStdout(r.stdio.Out), userOut); err != nil {
 		return err
 	}
@@ -130,16 +129,11 @@ func (r *Renderer) AppendRenderedText(text string) {
 	r.renderedText.WriteString(text)
 }
 
+// resetPrompt clears the previous lines of the past prompt
 func (r *Renderer) resetPrompt(lines int) {
-	// clean out current line in case tmpl didnt end in newline
 	cursor := r.NewCursor()
-	cursor.HorizontalAbsolute(0)
-	terminal.EraseLine(r.stdio.Out, terminal.ERASE_LINE_ALL)
-	// clean up what we left behind last time
-	for i := 0; i < lines; i++ {
-		cursor.PreviousLine(1)
-		terminal.EraseLine(r.stdio.Out, terminal.ERASE_LINE_ALL)
-	}
+	cursor.PreviousLine(lines)
+	terminal.EraseScreen(r.stdio.Out, terminal.ERASE_SCREEN_END)
 }
 
 func (r *Renderer) termWidth() (int, error) {
@@ -161,8 +155,7 @@ func (r *Renderer) termWidthSafe() int {
 // countLines will return the count of `\n` with the addition of any
 // lines that have wrapped due to narrow terminal width
 func (r *Renderer) countLines(buf bytes.Buffer) int {
-	w := r.termWidthSafe()
-
+	termWidth := r.termWidthSafe()
 	bufBytes := buf.Bytes()
 
 	count := 0
@@ -179,10 +172,11 @@ func (r *Renderer) countLines(buf bytes.Buffer) int {
 		}
 
 		str := string(bufBytes[curr:delim])
-		if lineWidth := terminal.StringWidth(str); lineWidth > w {
+		lineWidth := terminal.StringWidth(str)
+		if lineWidth > termWidth {
 			// account for word wrapping
-			count += lineWidth / w
-			if (lineWidth % w) == 0 {
+			count += lineWidth / termWidth
+			if (lineWidth % termWidth) == 0 {
 				// content whose width is exactly a multiplier of available width should not
 				// count as having wrapped on the last line
 				count -= 1

terminal/cursor.go

@@ -47,18 +47,24 @@ func (c *Cursor) Back(n int) error {
 
 // NextLine moves cursor to beginning of the line n lines down.
 func (c *Cursor) NextLine(n int) error {
-	if err := c.Down(1); err != nil {
+	if err := c.HorizontalAbsolute(0); err != nil {
 		return err
 	}
-	return c.HorizontalAbsolute(0)
+	if n == 0 {
+		return nil
+	}
+	return c.Down(n)
 }
 
 // PreviousLine moves cursor to beginning of the line n lines up.
 func (c *Cursor) PreviousLine(n int) error {
-	if err := c.Up(1); err != nil {
+	if err := c.HorizontalAbsolute(0); err != nil {
 		return err
 	}
-	return c.HorizontalAbsolute(0)
+	if n == 0 {
+		return nil
+	}
+	return c.Up(n)
 }
 
 // HorizontalAbsolute moves cursor horizontally to x.

terminal/display.go

@@ -1,9 +1,16 @@
 package terminal
 
 type EraseLineMode int
+type EraseScreenMode int
 
 const (
 	ERASE_LINE_END EraseLineMode = iota
 	ERASE_LINE_START
 	ERASE_LINE_ALL
 )
+
+const (
+	ERASE_SCREEN_END EraseScreenMode = iota
+	ERASE_SCREEN_START
+	ERASE_SCREEN_ALL
+)

terminal/display_posix.go

@@ -11,3 +11,8 @@ func EraseLine(out FileWriter, mode EraseLineMode) error {
 	_, err := fmt.Fprintf(out, "\x1b[%dK", mode)
 	return err
 }
+
+func EraseScreen(out FileWriter, mode EraseScreenMode) error {
+	_, err := fmt.Fprintf(out, "\x1b[%dJ", mode)
+	return err
+}

terminal/display_windows.go

@@ -29,3 +29,22 @@ func EraseLine(out FileWriter, mode EraseLineMode) error {
 	_, _, err := procFillConsoleOutputCharacter.Call(uintptr(handle), uintptr(' '), uintptr(x), uintptr(*(*int32)(unsafe.Pointer(&cursor))), uintptr(unsafe.Pointer(&w)))
 	return normalizeError(err)
 }
+
+func EraseScreen(out FileWriter, mode EraseScreenMode) error {
+	handle := syscall.Handle(out.Fd())
+
+	var csbi consoleScreenBufferInfo
+	if _, _, err := procGetConsoleScreenBufferInfo.Call(uintptr(handle), uintptr(unsafe.Pointer(&csbi))); normalizeError(err) != nil {
+		return err
+	}
+
+	var w uint32
+	cursor := csbi.cursorPosition
+
+	lineCount := csbi.window.bottom - csbi.cursorPosition.Y
+	termWidth := csbi.size.X
+	screenSize := lineCount * termWidth
+
+	_, _, err := procFillConsoleOutputCharacter.Call(uintptr(handle), uintptr(' '), uintptr(screenSize), uintptr(*(*int32)(unsafe.Pointer(&cursor))), uintptr(unsafe.Pointer(&w)))
+	return normalizeError(err)
+}