Clean up background processes when changing tutorial in fyne_demo

cmd/fyne_demo/main.go

@@ -228,6 +228,11 @@ func makeNav(setTutorial func(tutorial tutorials.Tutorial), loadPrevious bool) f
 		},
 		OnSelected: func(uid string) {
 			if t, ok := tutorials.Tutorials[uid]; ok {
+				for _, f := range tutorials.OnChangeFuncs {
+					f(uid)
+				}
+				tutorials.OnChangeFuncs = nil // Loading a page registers a new cleanup.
+
 				a.Preferences().SetString(preferenceCurrentTutorial, uid)
 				setTutorial(t)
 			}

cmd/fyne_demo/tutorials/advanced.go

@@ -36,8 +36,16 @@ func advancedScreen(win fyne.Window) fyne.CanvasObject {
 		&widget.FormItem{Text: "Texture Scale", Widget: tex},
 	))
 
+	ticker := time.NewTicker(time.Second)
+
+	OnChangeFuncs = append(OnChangeFuncs, func(page string) {
+		if page != "advanced" {
+			ticker.Stop()
+		}
+	})
+
 	go func(canvas fyne.Canvas) {
-		for range time.NewTicker(time.Second).C {
+		for range ticker.C {
 			fyne.Do(func() {
 				scale.SetText(scaleToString(canvas))
 				tex.SetText(textureScaleToString(canvas))

cmd/fyne_demo/tutorials/animation.go

@@ -46,6 +46,13 @@ func makeAnimationCanvas() fyne.CanvasObject {
 	a2.Curve = fyne.AnimationLinear
 	a2.Start()
 
+	OnChangeFuncs = append(OnChangeFuncs, func(page string) {
+		if page != "animations" {
+			a.Stop()
+			a2.Stop()
+		}
+	})
+
 	running := true
 	var toggle *widget.Button
 	toggle = widget.NewButton("Stop", func() {
@@ -71,6 +78,15 @@ func makeAnimationCurves() fyne.CanvasObject {
 	label3, box3, a3 := makeAnimationCurveItem("EaseOut", fyne.AnimationEaseOut, 60+theme.Padding()*2)
 	label4, box4, a4 := makeAnimationCurveItem("Linear", fyne.AnimationLinear, 90+theme.Padding()*3)
 
+	OnChangeFuncs = append(OnChangeFuncs, func(page string) {
+		if page != "animations" {
+			a1.Stop()
+			a2.Stop()
+			a3.Stop()
+			a4.Stop()
+		}
+	})
+
 	start := widget.NewButton("Compare", func() {
 		a1.Start()
 		a2.Start()

cmd/fyne_demo/tutorials/canvas.go

@@ -20,8 +20,16 @@ func rgbGradient(x, y, w, h int) color.Color {
 // canvasScreen loads a graphics example panel for the demo app
 func canvasScreen(_ fyne.Window) fyne.CanvasObject {
 	gradient := canvas.NewHorizontalGradient(color.NRGBA{0x80, 0, 0, 0xff}, color.NRGBA{0, 0x80, 0, 0xff})
+	ticker := time.NewTicker(time.Second)
+
+	OnChangeFuncs = append(OnChangeFuncs, func(page string) {
+		if page != "canvas" {
+			ticker.Stop()
+		}
+	})
+
 	go func() {
-		for range time.NewTicker(time.Second).C {
+		for range ticker.C {
 			fyne.Do(func() {
 				gradient.Angle += 45
 				if gradient.Angle >= 360 {

cmd/fyne_demo/tutorials/data.go

@@ -4,6 +4,10 @@ import (
 	"fyne.io/fyne/v2"
 )
 
+// OnChangeFuncs is a slice of functions that can be registered
+// to run when the user switches tutorial.
+var OnChangeFuncs []func(string)
+
 // Tutorial defines the data structure for a tutorial
 type Tutorial struct {
 	Title, Intro string

cmd/fyne_demo/tutorials/widget.go

@@ -405,7 +405,25 @@ func makeProgressTab(_ fyne.Window) fyne.CanvasObject {
 	}
 
 	infProgress := widget.NewProgressBarInfinite()
-	startProgress(progress, fprogress)
+
+	progressAnimation := fyne.Animation{
+		Curve:    fyne.AnimationLinear,
+		Duration: 10 * time.Second,
+		Tick: func(percentage float32) {
+			value := float64(percentage)
+			progress.SetValue(value)
+			fprogress.SetValue(value)
+		},
+	}
+
+	progressAnimation.Start()
+
+	OnChangeFuncs = append(OnChangeFuncs, func(page string) {
+		if page != "progress" {
+			progressAnimation.Stop()
+			infProgress.Stop()
+		}
+	})
 
 	return container.NewVBox(
 		widget.NewLabel("Percent"), progress,
@@ -463,20 +481,6 @@ func makeToolbarTab(_ fyne.Window) fyne.CanvasObject {
 	return container.NewBorder(t, nil, nil, nil)
 }
 
-func startProgress(progress, fprogress *widget.ProgressBar) {
-	progressAnimation := fyne.Animation{
-		Curve:    fyne.AnimationLinear,
-		Duration: 10 * time.Second,
-		Tick: func(percentage float32) {
-			value := float64(percentage)
-			progress.SetValue(value)
-			fprogress.SetValue(value)
-		},
-	}
-
-	progressAnimation.Start()
-}
-
 // widgetScreen shows a panel containing widget demos
 func widgetScreen(_ fyne.Window) fyne.CanvasObject {
 	content := container.NewVBox(