Maximum width and height of drawing, in inches. If only a single number is given, this is used for both the width and the height.

If defined and the drawing is larger than the given size, the drawing is uniformly scaled down so that it fits within the given size.

If size ends in an exclamation point (!), then it is taken to be the desired size. In this case, if both dimensions of the drawing are less than size, the drawing is scaled up uniformly until at least one dimension equals its dimension in size.

Note that there is some interaction between the size and ratio attributes.