widget/material: add ProgressCircle

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/material/progresscircle.go

@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package material
+
+import (
+	"image"
+	"image/color"
+	"math"
+
+	"gioui.org/f32"
+	"gioui.org/layout"
+	"gioui.org/op"
+	"gioui.org/op/paint"
+	"gioui.org/unit"
+)
+
+type ProgressCircleStyle struct {
+	Color    color.NRGBA
+	Progress float32
+}
+
+func ProgressCircle(th *Theme, progress float32) ProgressCircleStyle {
+	return ProgressCircleStyle{
+		Color:    th.Palette.ContrastBg,
+		Progress: progress,
+	}
+}
+
+func (p ProgressCircleStyle) Layout(gtx layout.Context) layout.Dimensions {
+	diam := gtx.Constraints.Min.X
+	if minY := gtx.Constraints.Min.Y; minY > diam {
+		diam = minY
+	}
+	if diam == 0 {
+		diam = gtx.Px(unit.Dp(24))
+	}
+	sz := gtx.Constraints.Constrain(image.Pt(diam, diam))
+	radius := float32(sz.X) * .5
+	defer op.Save(gtx.Ops).Load()
+	op.Offset(f32.Pt(radius, radius)).Add(gtx.Ops)
+
+	clipLoader(gtx.Ops, -math.Pi/2, -math.Pi/2+math.Pi*2*p.Progress, radius)
+	paint.ColorOp{
+		Color: p.Color,
+	}.Add(gtx.Ops)
+	op.Offset(f32.Pt(-radius, -radius)).Add(gtx.Ops)
+	paint.PaintOp{}.Add(gtx.Ops)
+	return layout.Dimensions{
+		Size: sz,
+	}
+}