Merge pull request #88 from Kirides/master

add option to support ANSI escape code compatible environments

Author: schollz

progressbar.go

@@ -93,6 +93,9 @@ type config struct {
 	invisible bool
 
 	onCompletion func()
+
+	// whether the render function should make use of ANSI codes to reduce console I/O
+	useANSICodes bool
 }
 
 // Theme defines the elements of the bar
@@ -229,6 +232,15 @@ func OptionShowBytes(val bool) Option {
 	}
 }
 
+// OptionUseANSICodes will use more optimized terminal i/o.
+//
+// Only useful in environments with support for ANSI escape sequences.
+func OptionUseANSICodes(val bool) Option {
+	return func(p *ProgressBar) {
+		p.config.useANSICodes = val
+	}
+}
+
 var defaultTheme = Theme{Saucer: "█", SaucerPadding: " ", BarStart: "|", BarEnd: "|"}
 
 // NewOptions constructs a new instance of ProgressBar, with any options you specify
@@ -496,10 +508,12 @@ func (p *ProgressBar) render() error {
 		return nil
 	}
 
-	// first, clear the existing progress bar
-	err := clearProgressBar(p.config, p.state)
-	if err != nil {
-		return err
+	if !p.config.useANSICodes {
+		// first, clear the existing progress bar
+		err := clearProgressBar(p.config, p.state)
+		if err != nil {
+			return err
+		}
 	}
 
 	// check if the progress bar is finished
@@ -514,6 +528,13 @@ func (p *ProgressBar) render() error {
 		}
 	}
 	if p.state.finished {
+		// when using ANSI codes we don't pre-clean the current line
+		if p.config.useANSICodes {
+			err := clearProgressBar(p.config, p.state)
+			if err != nil {
+				return err
+			}
+		}
 		return nil
 	}
 
@@ -724,11 +745,18 @@ func renderProgressBar(c config, s state) (int, error) {
 	// character count of the string, as some runes span multiple characters.
 	// see https://stackoverflow.com/a/12668840/2733724
 	stringWidth := runewidth.StringWidth(cleanString)
-
+	if c.useANSICodes {
+		// append the "clear rest of line" ANSI escape sequence
+		str = str + "\033[0K"
+	}
 	return stringWidth, writeString(c, str)
 }
 
 func clearProgressBar(c config, s state) error {
+	if c.useANSICodes {
+		// write the "clear current line" ANSI escape sequence
+		return writeString(c, "\033[2K\r")
+	}
 	// fill the current line with enough spaces
 	// to overwrite the progress bar and jump
 	// back to the beginning of the line