Fix #327: show loading dots when search in progress but no results yet

ui/widgets/loadingdots.go

@@ -0,0 +1,118 @@
+package widgets
+
+import (
+	"context"
+	"image/color"
+	"sync/atomic"
+	"time"
+
+	"fyne.io/fyne/v2"
+	"fyne.io/fyne/v2/canvas"
+	"fyne.io/fyne/v2/container"
+	"fyne.io/fyne/v2/theme"
+	"fyne.io/fyne/v2/widget"
+	"github.com/dweymouth/supersonic/ui/layouts"
+)
+
+type LoadingDots struct {
+	widget.BaseWidget
+
+	running    atomic.Bool
+	animCancel context.CancelFunc
+
+	dots      [3]minSizeCircle
+	animPos   int
+	container *fyne.Container
+}
+
+func NewLoadingDots() *LoadingDots {
+	l := &LoadingDots{}
+	for i := range l.dots {
+		l.dots[i] = minSizeCircle{Circle: canvas.Circle{
+			FillColor: theme.DisabledColor()},
+		}
+	}
+	l.ExtendBaseWidget(l)
+	l.Hide()
+	return l
+}
+
+func (l *LoadingDots) Start() {
+	if !l.running.CompareAndSwap(false, true) {
+		return // already started
+	}
+	for i := range l.dots {
+		l.dots[i].Circle.FillColor = theme.DisabledColor()
+	}
+	l.animPos = 0
+	l.Show()
+	var ctx context.Context
+	ctx, l.animCancel = context.WithCancel(context.Background())
+	go l.animate(ctx)
+}
+
+func (l *LoadingDots) Stop() {
+	if !l.running.Load() {
+		return
+	}
+	l.Hide()
+	l.animCancel()
+}
+
+func (l *LoadingDots) animate(ctx context.Context) {
+	foreground := theme.ForegroundColor()
+	disabled := theme.DisabledColor()
+	l.doTick(foreground, disabled)
+	ticker := time.NewTicker(333 * time.Millisecond)
+	for {
+		select {
+		case <-ctx.Done():
+			ticker.Stop()
+			l.running.Store(false)
+			return
+		case <-ticker.C:
+			l.doTick(foreground, disabled)
+		}
+	}
+}
+
+func (l *LoadingDots) doTick(foreground, disabled color.Color) {
+	oldDot := l.animPos - 1
+	if oldDot == -1 {
+		oldDot = len(l.dots) - 1
+	}
+	l.dots[l.animPos].Circle.FillColor = foreground
+	l.dots[oldDot].Circle.FillColor = disabled
+	l.Refresh()
+	l.animPos += 1
+	if l.animPos >= len(l.dots) {
+		l.animPos = 0
+	}
+}
+
+func (l *LoadingDots) CreateRenderer() fyne.WidgetRenderer {
+	if l.container == nil {
+		layout := &layouts.CenterPadLayout{
+			PadLeftRight: 3,
+		}
+		l.container = container.NewHBox(
+			container.New(layout, &l.dots[0]),
+			container.New(layout, &l.dots[1]),
+			container.New(layout, &l.dots[2]),
+		)
+	}
+	return widget.NewSimpleRenderer(l.container)
+}
+
+type minSizeCircle struct {
+	widget.BaseWidget
+	Circle canvas.Circle
+}
+
+func (m *minSizeCircle) CreateRenderer() fyne.WidgetRenderer {
+	return widget.NewSimpleRenderer(&m.Circle)
+}
+
+func (m *minSizeCircle) MinSize() fyne.Size {
+	return fyne.NewSquareSize(theme.IconInlineSize() / 2)
+}