triangle.go

package main

import (
	"image/color"

	"gioui.org/app"
	"gioui.org/f32"
	"gioui.org/io/system"
	"gioui.org/op"
	"gioui.org/op/clip"
	"gioui.org/op/paint"
)

func main() {
	go func() {
		w := app.NewWindow()

		ops := new(op.Ops)
		for e := range w.Events() {
			if e, ok := e.(system.FrameEvent); ok {
				ops.Reset()
				r := f32.Rectangle{
					Max: f32.Point{X: 400, Y: 400},
				}

				p := &clip.Path{}
				p.Begin(ops)
				//<svg height="210" width="400">
				//  <path d="M150 0 L75 200 L225 200 Z" />
				//</svg>
				p.Move(f32.Point{X: 150, Y: 0})
				p.Line(f32.Point{X: 75, Y: 200})
				p.Line(f32.Point{X: 225, Y: 200})
				p.Line(f32.Point{X: 150, Y: 0})
				p.End().Add(ops)

				paint.ColorOp{Color: color.RGBA{A: 0xff}}.Add(ops)
				paint.PaintOp{Rect: r}.Add(ops)

				e.Frame(ops)
			}
		}
	}()
	app.Main()
}