package main

import (
	"image"
	"image/color"
	"log"
	"os"

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

func main() {
	go func() {
		w := app.NewWindow()
		err := run(w)
		if err != nil {
			log.Fatal(err)
		}
		os.Exit(0)
	}()
	app.Main()
}

func run(w *app.Window) error {
	var ops op.Ops
	for {
		e := <-w.Events()
		switch e := e.(type) {
		case system.DestroyEvent:
			return e.Err
		case system.FrameEvent:
			gtx := layout.NewContext(&ops, e)

			// Using clip.Rect
			{
				stack := op.Affine(f32.Affine2D{}.Offset(f32.Pt(50.3, 50.3))).Push(&ops)
				r1 := clip.Rect{Max: image.Pt(50, 50)}
				paint.FillShape(&ops, color.NRGBA{0xFF, 0, 0, 0xFF}, r1.Op())
				stack.Pop()
			}

			// Drawing our own rectangular path
			{
				stack := op.Affine(f32.Affine2D{}.Offset(f32.Pt(50.3, 150.3))).Push(&ops)
				r1 := FRect{Max: f32.Pt(50, 50)}
				paint.FillShape(&ops, color.NRGBA{0xFF, 0, 0, 0xFF}, r1.Op(&ops))
				stack.Pop()
			}

			e.Frame(gtx.Ops)
		}
	}
}

type FRect struct {
	Min f32.Point
	Max f32.Point
}

func (r FRect) Path(ops *op.Ops) clip.PathSpec {
	var p clip.Path
	p.Begin(ops)
	p.MoveTo(r.Min)
	p.LineTo(f32.Pt(r.Max.X, r.Min.Y))
	p.LineTo(r.Max)
	p.LineTo(f32.Pt(r.Min.X, r.Max.Y))
	p.LineTo(r.Min)
	return p.End()
}

func (r FRect) Op(ops *op.Ops) clip.Op {
	return clip.Outline{Path: r.Path(ops)}.Op()
}