func newBox(cvs *canvas.Canvas, r draw.Rectangle) *box {
var b box
red := image.Uniform{image.Red}
b.n = canvas.NewLine(red, r.Min, draw.Pt(r.Max.X, r.Min.Y), 1)
b.e = canvas.NewLine(red, draw.Pt(r.Max.X, r.Min.Y), r.Max, 1)
b.s = canvas.NewLine(red, r.Max, draw.Pt(r.Min.X, r.Max.Y), 1)
b.w = canvas.NewLine(red, draw.Pt(r.Min.X, r.Max.Y), r.Min, 1)
cvs.AddItem(b.n)
cvs.AddItem(b.e)
cvs.AddItem(b.s)
cvs.AddItem(b.w)
return &b
}
func dragRect(cvs *canvas.Canvas, m draw.Mouse, mc <-chan draw.Mouse) draw.Rectangle {
m0 := m
r := draw.Rectangle{m0.Point, m0.Point}
b := newBox(cvs, r)
cvs.Flush()
for m.Buttons != 0 {
m = <-mc
b.setRect(draw.Rectangle{m0.Point, m.Point}.Canon())
cvs.Flush()
}
b.delete(cvs)
cvs.Flush()
return draw.Rectangle{m0.Point, m.Point}.Canon()
}
func (b *box) delete(cvs *canvas.Canvas) {
cvs.Delete(b.n)
cvs.Delete(b.e)
cvs.Delete(b.s)
cvs.Delete(b.w)
}