Add a new widget for activity indication

cmd/fyne_demo/tutorials/data.go

@@ -88,6 +88,11 @@ var (
 			makeAccordionTab,
 			true,
 		},
+		"activity": {"Activity",
+			"A spinner indicating activity used in buttons etc.",
+			makeActivityTab,
+			true,
+		},
 		"button": {"Button",
 			"Simple widget for user tap handling.",
 			makeButtonTab,
@@ -182,6 +187,6 @@ var (
 		"":            {"welcome", "canvas", "animations", "icons", "widgets", "collections", "containers", "dialogs", "windows", "binding", "advanced"},
 		"collections": {"list", "table", "tree", "gridwrap"},
 		"containers":  {"apptabs", "border", "box", "center", "doctabs", "grid", "scroll", "split"},
-		"widgets":     {"accordion", "button", "card", "entry", "form", "input", "progress", "text", "toolbar"},
+		"widgets":     {"accordion", "activity", "button", "card", "entry", "form", "input", "progress", "text", "toolbar"},
 	}
 )

cmd/fyne_demo/tutorials/widget.go

@@ -55,6 +55,53 @@ func makeAccordionTab(_ fyne.Window) fyne.CanvasObject {
 	return ac
 }
 
+func makeActivityTab(_ fyne.Window) fyne.CanvasObject {
+	a1 := widget.NewActivity()
+	a2 := widget.NewActivity()
+	a3 := widget.NewActivity()
+
+	prop := canvas.NewRectangle(color.Transparent)
+	prop.SetMinSize(fyne.NewSize(160, 80))
+
+	var button *widget.Button
+	start := func() {
+		button.Disable()
+		a1.Start()
+		a1.Show()
+		a2.Start()
+		a2.Show()
+		a3.Start()
+		a3.Show()
+
+		defer func() {
+			go func() {
+				time.Sleep(time.Second * 10)
+				a1.Stop()
+				a1.Hide()
+				a2.Stop()
+				a2.Hide()
+				a3.Stop()
+				a3.Hide()
+
+				button.Enable()
+			}()
+		}()
+	}
+
+	button = widget.NewButton("Animate", start)
+	start()
+
+	fakeDialog := container.NewStack(canvas.NewRectangle(theme.OverlayBackgroundColor()),
+		container.NewVBox(widget.NewLabelWithStyle("Dialog, e.g.", fyne.TextAlignLeading, fyne.TextStyle{Bold: true}),
+			container.NewStack(prop, a3)))
+
+	return container.NewCenter(container.NewGridWithColumns(1,
+		container.NewCenter(container.NewVBox(
+			container.NewHBox(widget.NewLabel("Working..."), a1),
+			container.NewStack(button, a2))),
+		container.NewCenter(fakeDialog)))
+}
+
 func makeButtonTab(_ fyne.Window) fyne.CanvasObject {
 	disabled := widget.NewButton("Disabled", func() {})
 	disabled.Disable()

widget/activity.go

@@ -0,0 +1,145 @@
+package widget
+
+import (
+	"image/color"
+	"time"
+
+	"fyne.io/fyne/v2"
+	"fyne.io/fyne/v2/canvas"
+	"fyne.io/fyne/v2/internal/cache"
+	"fyne.io/fyne/v2/theme"
+)
+
+var _ fyne.Widget = (*Activity)(nil)
+
+// Activity is used to indicate that something is happening that should be waited for,
+// or is in the background (depending on usage).
+type Activity struct {
+	BaseWidget
+}
+
+// NewActivity returns a widget for indicating activity
+func NewActivity() *Activity {
+	a := &Activity{}
+	a.ExtendBaseWidget(a)
+	return a
+}
+
+func (a *Activity) MinSize() fyne.Size {
+	a.ExtendBaseWidget(a)
+
+	return fyne.NewSquareSize(theme.IconInlineSize())
+}
+
+// Start the activity indicator animation
+func (a *Activity) Start() {
+	if r, ok := cache.Renderer(a.super()).(*activityRenderer); ok {
+		r.start()
+	}
+}
+
+// Stop the activity indicator animation
+func (a *Activity) Stop() {
+	if r, ok := cache.Renderer(a.super()).(*activityRenderer); ok {
+		r.stop()
+	}
+}
+
+func (a *Activity) CreateRenderer() fyne.WidgetRenderer {
+	dots := make([]fyne.CanvasObject, 3)
+	for i := range dots {
+		dots[i] = canvas.NewCircle(theme.ForegroundColor())
+	}
+	r := &activityRenderer{dots: dots}
+	r.anim = &fyne.Animation{
+		//		Curve: fyne.AnimationEaseOut,
+		Duration:    time.Second * 2,
+		RepeatCount: fyne.AnimationRepeatForever,
+		Tick:        r.animate}
+	r.updateColor()
+	return r
+}
+
+var _ fyne.WidgetRenderer = (*activityRenderer)(nil)
+
+type activityRenderer struct {
+	anim *fyne.Animation
+	dots []fyne.CanvasObject
+
+	bound  fyne.Size
+	maxCol color.NRGBA
+	maxRad float32
+}
+
+func (a *activityRenderer) Destroy() {
+	a.stop()
+}
+
+func (a *activityRenderer) Layout(size fyne.Size) {
+	a.maxRad = fyne.Min(size.Width, size.Height) / 2
+	a.bound = size
+}
+
+func (a *activityRenderer) MinSize() fyne.Size {
+	return fyne.NewSquareSize(theme.IconInlineSize())
+}
+
+func (a *activityRenderer) Objects() []fyne.CanvasObject {
+	return a.dots
+}
+
+func (a *activityRenderer) Refresh() {
+	a.updateColor()
+}
+
+func (a *activityRenderer) animate(done float32) {
+	off := done * 2
+	if off > 1 {
+		off = 2 - off
+	}
+
+	off1 := (done + 0.25) * 2
+	if done >= 0.75 {
+		off1 = (done - 0.75) * 2
+	}
+	if off1 > 1 {
+		off1 = 2 - off1
+	}
+
+	off2 := (done + 0.75) * 2
+	if done >= 0.25 {
+		off2 = (done - 0.25) * 2
+	}
+	if off2 > 1 {
+		off2 = 2 - off2
+	}
+
+	a.scaleDot(a.dots[0].(*canvas.Circle), off)
+	a.scaleDot(a.dots[1].(*canvas.Circle), off1)
+	a.scaleDot(a.dots[2].(*canvas.Circle), off2)
+}
+
+func (a *activityRenderer) scaleDot(dot *canvas.Circle, off float32) {
+	rad := a.maxRad - a.maxRad*off/1.2
+	mid := fyne.NewPos(a.bound.Width/2, a.bound.Height/2)
+
+	dot.Move(mid.Subtract(fyne.NewSquareOffsetPos(rad)))
+	dot.Resize(fyne.NewSquareSize(rad * 2))
+
+	alpha := uint8(0 + int(float32(a.maxCol.A)*off))
+	dot.FillColor = color.NRGBA{R: a.maxCol.R, G: a.maxCol.G, B: a.maxCol.B, A: alpha}
+	dot.Refresh()
+}
+
+func (a *activityRenderer) start() {
+	a.anim.Start()
+}
+
+func (a *activityRenderer) stop() {
+	a.anim.Stop()
+}
+
+func (a *activityRenderer) updateColor() {
+	rr, gg, bb, aa := theme.ForegroundColor().RGBA()
+	a.maxCol = color.NRGBA{R: uint8(rr >> 8), G: uint8(gg >> 8), B: uint8(bb >> 8), A: uint8(aa >> 8)}
+}