# File lib/rvg/stretchable.rb, line 132
        def viewbox(x, y, width, height)
            begin
                @vbx_x = Float(x)
                @vbx_y = Float(y)
                @vbx_width = Float(width)
                @vbx_height = Float(height)
            rescue ArgumentError
                raise ArgumentError, "arguments must be convertable to float (got #{x.class}, #{y.class}, #{width.class}, #{height.class})"
            end
            raise(ArgumentError, "viewbox width must be > 0 (#{width} given)") unless width >= 0
            raise(ArgumentError, "viewbox height must be > 0 (#{height} given)") unless height >= 0
            yield(self) if block_given?
            self
        end