func Grid(canvas *pdf.Canvas, x, y, w, h, step float64) {
canvas.Push()
canvas.SetColor(0.75, 0.75, 0.75)
canvas.Translate(unit(x), unit(y))
rowCount := int(math.Floor(h / step))
for row := 0; row < rowCount; row++ {
bottom := float64(row) * step
top := bottom + step
start := 0.0
if row%2 == 0 {
start += step
}
for left := start; left < w; left += (2 * step) {
right := left + step
bottomLeft := point(left, bottom)
topRight := point(right, top)
path := new(pdf.Path)
path.Rectangle(pdf.Rectangle{bottomLeft, topRight})
canvas.Fill(path)
}
}
canvas.Pop()
}
