Animated Saucer Head

examples/pacman/main.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/k0kubun/go-ansi"
+	"github.com/schollz/progressbar/v3"
+)
+
+func main() {
+	doneCh := make(chan struct{})
+
+	bar := progressbar.NewOptions(1000,
+		progressbar.OptionSetWriter(ansi.NewAnsiStdout()),
+		progressbar.OptionEnableColorCodes(true),
+		progressbar.OptionSetWidth(50),
+		progressbar.OptionSetTheme(progressbar.Theme{
+			Saucer:        " ",
+			AltSaucerHead: "[yellow]<[reset]",
+			SaucerHead:    "[yellow]-[reset]",
+			SaucerPadding: "[white]•",
+			BarStart:      "[blue]|[reset]",
+			BarEnd:        "[blue]|[reset]",
+		}),
+		progressbar.OptionOnCompletion(func() {
+			doneCh <- struct{}{}
+		}),
+	)
+
+	go func() {
+		for i := 0; i < 1000; i++ {
+			bar.Add(1)
+			time.Sleep(10 * time.Millisecond)
+		}
+	}()
+
+	// got notified that progress bar is complete.
+	<-doneCh
+	fmt.Println("\n ======= progress bar completed ==========\n")
+}

progressbar.go

@@ -39,6 +39,7 @@ type state struct {
 	currentPercent    int
 	lastPercent       int
 	currentSaucerSize int
+	isAltSaucerHead   bool
 
 	lastShown time.Time
 	startTime time.Time
@@ -104,6 +105,7 @@ type config struct {
 // Theme defines the elements of the bar
 type Theme struct {
 	Saucer        string
+	AltSaucerHead string
 	SaucerHead    string
 	SaucerPadding string
 	BarStart      string
@@ -655,6 +657,7 @@ func renderProgressBar(c config, s *state) (int, error) {
 	leftBrac := ""
 	rightBrac := ""
 	saucer := ""
+	saucerHead := ""
 	bytesString := ""
 	str := ""
 
@@ -754,11 +757,18 @@ func renderProgressBar(c config, s *state) (int, error) {
 		} else {
 			saucer = strings.Repeat(c.theme.Saucer, s.currentSaucerSize-1)
 		}
-		saucerHead := c.theme.SaucerHead
-		if saucerHead == "" || s.currentSaucerSize == c.width {
+
+		// Check if an alternate saucer head is set for animation
+		if c.theme.AltSaucerHead != "" && s.isAltSaucerHead {
+			saucerHead = c.theme.AltSaucerHead
+			s.isAltSaucerHead = false
+		} else if c.theme.SaucerHead == "" || s.currentSaucerSize == c.width {
 			// use the saucer for the saucer head if it hasn't been set
 			// to preserve backwards compatibility
 			saucerHead = c.theme.Saucer
+		} else {
+			saucerHead = c.theme.SaucerHead
+			s.isAltSaucerHead = true
 		}
 		saucer += saucerHead
 	}