'Projected rendering envelope (xmin, ymin, xmax, ymax) for a Coordinate.'

def envelope(self, coord):

    ul = self.projection.coordinateProj(coord)
    lr = self.projection.coordinateProj(coord.down().right())
    return (min(ul.x, lr.x), min(ul.y, lr.y), max(ul.x, lr.x), max(ul.y, lr.y))
