drafting

tracker/gioui/port.go

@@ -0,0 +1,66 @@
+package gioui
+
+import (
+	"image"
+	"image/color"
+	"math"
+
+	"gioui.org/f32"
+	"gioui.org/gesture"
+	"gioui.org/io/event"
+	"gioui.org/op/clip"
+	"gioui.org/op/paint"
+	"gioui.org/unit"
+)
+
+type (
+	PortState struct {
+		click gesture.Click
+	}
+
+	PortStyle struct {
+		Diameter    unit.Dp
+		StrokeWidth unit.Dp
+		Color       color.NRGBA
+	}
+
+	PortWidget struct {
+		Theme *Theme
+		Style *PortStyle
+		State *PortState
+	}
+)
+
+func Port(t *Theme, p *PortState) PortWidget {
+	return PortWidget{Theme: t, Style: &t.Port, State: p}
+}
+
+func (p *PortWidget) Layout(gtx C) D {
+	d := gtx.Dp(p.Style.Diameter)
+	defer clip.Rect(image.Rectangle{Max: image.Pt(d, d)}).Push(gtx.Ops).Pop()
+	event.Op(gtx.Ops, p.State)
+	p.State.click.Add(gtx.Ops)
+	p.strokeCircle(gtx)
+	return D{Size: image.Pt(d, d)}
+}
+
+func (p *PortState) Clicked(gtx C) bool {
+	ev, ok := p.click.Update(gtx.Source)
+	return ok && ev.Kind == gesture.KindClick
+}
+
+func (p *PortWidget) strokeCircle(gtx C) {
+	sw := float32(gtx.Dp(p.Style.StrokeWidth))
+	d := float32(gtx.Dp(p.Style.Diameter))
+	rad := d / 2
+	center := f32.Point{X: rad, Y: rad}
+	var path clip.Path
+	path.Begin(gtx.Ops)
+	path.MoveTo(f32.Pt(sw/2, rad))
+	path.ArcTo(center, center, float32(math.Pi*2))
+	paint.FillShape(gtx.Ops, p.Style.Color,
+		clip.Stroke{
+			Path:  path.End(),
+			Width: sw,
+		}.Op())
+}