add throttle

examples/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"os"
 	"time"
 
 	ansi "github.com/k0kubun/go-ansi"
@@ -17,15 +18,16 @@ func main() {
 		time.Sleep(2 * time.Millisecond)
 	}
 
-	// // bar with options
-	// bar = progressbar.NewOptions(1000,
-	// 	progressbar.OptionSetWriter(os.Stderr),
-	// 	progressbar.OptionSetTheme(progressbar.Theme{Saucer: "~", SaucerPadding: "-", BarStart: "|", BarEnd: "|"}),
-	// )
-	// for i := 0; i < 1000; i++ {
-	// 	bar.Add(1)
-	// 	time.Sleep(2 * time.Millisecond)
-	// }
+	// bar with options
+	bar = progressbar.NewOptions(1000,
+		progressbar.OptionSetWriter(os.Stderr),
+		progressbar.OptionSetTheme(progressbar.Theme{Saucer: "~", SaucerPadding: "-", BarStart: "|", BarEnd: "|"}),
+		progressbar.OptionThrottle(100*time.Millisecond),
+	)
+	for i := 0; i < 1000; i++ {
+		bar.Add(1)
+		time.Sleep(2 * time.Millisecond)
+	}
 
 	bar = progressbar.NewOptions(100,
 		progressbar.OptionSetWriter(ansi.NewAnsiStdout()),

progressbar.go

@@ -57,6 +57,9 @@ type config struct {
 	maxBytes   int
 	// show the iterations per second
 	showIterationsPerSecond bool
+
+	// minimum time to wait in between updates
+	throttleDuration time.Duration
 }
 
 // Theme defines the elements of the bar
@@ -128,17 +131,25 @@ func OptionShowIts() Option {
 	}
 }
 
+// OptionShowIts will also print the iterations/second
+func OptionThrottle(duration time.Duration) Option {
+	return func(p *ProgressBar) {
+		p.config.throttleDuration = duration
+	}
+}
+
 var defaultTheme = Theme{Saucer: "█", SaucerPadding: " ", BarStart: "|", BarEnd: "|"}
 
 // NewOptions constructs a new instance of ProgressBar, with any options you specify
 func NewOptions(max int, options ...Option) *ProgressBar {
 	b := ProgressBar{
 		state: getBlankState(),
 		config: config{
-			writer: os.Stdout,
-			theme:  defaultTheme,
-			width:  40,
-			max:    max,
+			writer:           os.Stdout,
+			theme:            defaultTheme,
+			width:            40,
+			max:              max,
+			throttleDuration: 0 * time.Nanosecond,
 		},
 	}
 
@@ -226,8 +237,16 @@ func (p *ProgressBar) Clear() error {
 // rendered line width. this function is not thread-safe,
 // so it must be called with an acquired lock.
 func (p *ProgressBar) render() error {
+	// make sure that the rendering is not happening too quickly
+	if time.Since(p.state.lastShown).Nanoseconds() < p.config.throttleDuration.Nanoseconds() {
+		return nil
+	}
+
 	// first, clear the existing progress bar
 	err := clearProgressBar(p.config, p.state)
+	if err != nil {
+		return err
+	}
 
 	// then, re-render the current progress bar
 	w, err := renderProgressBar(p.config, p.state)
@@ -239,6 +258,8 @@ func (p *ProgressBar) render() error {
 		p.state.maxLineWidth = w
 	}
 
+	p.state.lastShown = time.Now()
+
 	return nil
 }
 

progressbar_test.go

@@ -16,6 +16,16 @@ func ExampleProgressBar() {
 	// 10% |█         |  [1s:9s]
 }
 
+func ExampleThrottle() {
+	bar := NewOptions(100, OptionSetWidth(10), OptionSetRenderBlankState(false), OptionThrottle(100*time.Millisecond))
+	bar.Reset()
+	bar.Add(5)
+	time.Sleep(150 * time.Millisecond)
+	bar.Add(5)
+	bar.Add(10)
+	// Output:
+	// 10% |█         |  [0s:1s]
+}
 func ExampleFinish() {
 	bar := NewOptions(100, OptionSetWidth(10), OptionSetRenderBlankState(false))
 	bar.Reset()
@@ -102,7 +112,6 @@ func TestOptionSetTheme(t *testing.T) {
 		OptionSetWidth(10),
 		OptionSetWriter(&buf),
 	)
-
 	bar.Add(5)
 	result := strings.TrimSpace(buf.String())
 	expect := "50% >#####-----<  [0s:0s]"