package gioui

import (
	"image/color"

	"gioui.org/layout"
	"gioui.org/op/clip"
	"gioui.org/op/paint"
)

type Surface struct {
	Height int
	Inset  layout.Inset
	Focus  bool
}

func (s Surface) Layout(gtx C, widget layout.Widget) D {
	t := TrackerFromContext(gtx)
	t.surfaceHeight += s.Height
	bg := func(gtx C) D {
		gray := s.Height * 8
		if s.Focus {
			gray += 8
		}
		gray8 := uint8(min(max(gray, 0), 255))
		color := color.NRGBA{R: gray8, G: gray8, B: gray8, A: 255}
		paint.FillShape(gtx.Ops, color, clip.Rect{Max: gtx.Constraints.Min}.Op())
		return D{Size: gtx.Constraints.Min}
	}
	fg := func(gtx C) D { return s.Inset.Layout(gtx, widget) }
	dims := layout.Background{}.Layout(gtx, bg, fg)
	t.surfaceHeight -= s.Height
	return dims
}