    # File lib/rubygame/gfx.rb, line 555
      def zoom_to( width, height, smooth=false )
        zoomx = case width
                when nil;      1.0
                when Numeric;  width.to_f / @struct.w
                end

        zoomy = case height
                when nil;      1.0
                when Numeric;  height.to_f / @struct.h
                end

        return self.zoom( [zoomx, zoomy], smooth )
      end