widget/material: use clip.Circle to draw circles

Signed-off-by: Egon Elbre <egonelbre@gmail.com>

widget/material/checkable.go

@@ -5,7 +5,6 @@ package material
 import (
 	"image"
 	"image/color"
-	"math"
 
 	"gioui.org/f32"
 	"gioui.org/internal/f32color"
@@ -52,10 +51,12 @@ func (c *checkable) layout(gtx layout.Context, checked, hovered bool) layout.Dim
 
 					background := f32color.MulAlpha(c.IconColor, 70)
 
-					var p clip.Path
-					p.Begin(gtx.Ops)
-					addCircle(&p, float32(size)/2)
-					paint.FillShape(gtx.Ops, background, clip.Outline{Path: p.End()}.Op())
+					radius := float32(size) / 2
+					paint.FillShape(gtx.Ops, background,
+						clip.Circle{
+							Center: f32.Point{X: radius, Y: radius},
+							Radius: radius,
+						}.Op(gtx.Ops))
 
 					return dims
 				}),
@@ -85,14 +86,3 @@ func (c *checkable) layout(gtx layout.Context, checked, hovered bool) layout.Dim
 	pointer.Rect(image.Rectangle{Max: dims.Size}).Add(gtx.Ops)
 	return dims
 }
-
-// addCircle adds the outline of a circle to a path.
-func addCircle(p *clip.Path, r float32) {
-	// https://pomax.github.io/bezierinfo/#circles_cubic.
-	const c = 4 * (math.Sqrt2 - 1) / 3 // 4*(sqrt(2)-1)/3
-	p.Move(f32.Point{X: 2 * r, Y: 2*r - r})
-	p.Cube(f32.Point{X: 0, Y: r * c}, f32.Point{X: -r + r*c, Y: r}, f32.Point{X: -r, Y: r})
-	p.Cube(f32.Point{X: -r * c, Y: 0}, f32.Point{X: -r, Y: -r + r*c}, f32.Point{X: -r, Y: -r})
-	p.Cube(f32.Point{X: 0, Y: -r * c}, f32.Point{X: r - r*c, Y: -r}, f32.Point{X: r, Y: -r})
-	p.Cube(f32.Point{X: r * c, Y: 0}, f32.Point{X: r, Y: r - r*c}, f32.Point{X: r, Y: r})
-}

widget/material/slider.go

@@ -6,6 +6,7 @@ import (
 	"image"
 	"image/color"
 
+	"gioui.org/f32"
 	"gioui.org/internal/f32color"
 	"gioui.org/layout"
 	"gioui.org/op"
@@ -83,16 +84,12 @@ func (s SliderStyle) Layout(gtx layout.Context) layout.Dimensions {
 	st.Load()
 
 	// Draw thumb.
-	st = op.Save(gtx.Ops)
 	pt := axis.Convert(image.Pt(thumbPos, sizeCross/2))
-	rpt := image.Pt(thumbRadius, thumbRadius)
-	thumb := image.Rectangle{
-		Min: pt.Sub(rpt),
-		Max: pt.Add(rpt),
-	}
-	clip.UniformRRect(layout.FRect(thumb), float32(thumbRadius)).Add(gtx.Ops)
-	paint.Fill(gtx.Ops, color)
-	st.Load()
+	paint.FillShape(gtx.Ops, color,
+		clip.Circle{
+			Center: f32.Point{X: float32(pt.X), Y: float32(pt.Y)},
+			Radius: float32(thumbRadius),
+		}.Op(gtx.Ops))
 
 	return layout.Dimensions{Size: size}
 }

widget/material/switch.go

@@ -88,30 +88,34 @@ func (s SwitchStyle) Layout(gtx layout.Context) layout.Dimensions {
 		op.Offset(f32.Point{X: float32(off)}).Add(gtx.Ops)
 	}
 
+	thumbRadius := float32(thumbSize) / 2
+
 	// Draw hover.
 	if s.Switch.Hovered() {
-		var p clip.Path
-		r := 1.7 * float32(thumbSize) / 2
-		p.Begin(gtx.Ops)
-		//p.Move(f32.Pt(-float32(thumbSize)/2, -float32(thumbSize)/2))
-		p.Move(f32.Pt(-r+float32(thumbSize)/2, -r+float32(thumbSize)/2))
-		addCircle(&p, r)
+		r := 1.7 * thumbRadius
 		background := f32color.MulAlpha(s.Color.Enabled, 70)
-		paint.FillShape(gtx.Ops, background, clip.Outline{Path: p.End()}.Op())
+		paint.FillShape(gtx.Ops, background,
+			clip.Circle{
+				Center: f32.Point{X: thumbRadius, Y: thumbRadius},
+				Radius: r,
+			}.Op(gtx.Ops))
 	}
 
 	// Draw thumb shadow, a translucent disc slightly larger than the
 	// thumb itself.
-	shadowStack := op.Save(gtx.Ops)
-	shadowSize := float32(2)
 	// Center shadow horizontally and slightly adjust its Y.
-	op.Offset(f32.Point{X: -shadowSize / 2, Y: -.75}).Add(gtx.Ops)
-	drawDisc(gtx.Ops, float32(thumbSize)+shadowSize, argb(0x55000000))
-	shadowStack.Load()
+	paint.FillShape(gtx.Ops, argb(0x55000000),
+		clip.Circle{
+			Center: f32.Point{X: thumbRadius, Y: thumbRadius + .25},
+			Radius: thumbRadius + 1,
+		}.Op(gtx.Ops))
 
 	// Draw thumb.
-	drawDisc(gtx.Ops, float32(thumbSize), col)
-	stack.Load()
+	paint.FillShape(gtx.Ops, col,
+		clip.Circle{
+			Center: f32.Point{X: thumbRadius, Y: thumbRadius},
+			Radius: thumbRadius,
+		}.Op(gtx.Ops))
 
 	// Set up click area.
 	stack = op.Save(gtx.Ops)
@@ -130,11 +134,3 @@ func (s SwitchStyle) Layout(gtx layout.Context) layout.Dimensions {
 	dims := image.Point{X: trackWidth, Y: thumbSize}
 	return layout.Dimensions{Size: dims}
 }
-
-func drawDisc(ops *op.Ops, sz float32, col color.NRGBA) {
-	defer op.Save(ops).Load()
-	rr := sz / 2
-	clip.UniformRRect(f32.Rectangle{Max: f32.Pt(sz, sz)}, rr).Add(ops)
-	paint.ColorOp{Color: col}.Add(ops)
-	paint.PaintOp{}.Add(ops)
-}