Returns the best ratio of Width/Height to display this layer.

Some layer types look best at their original aspect ratio (i.e. the ratio of Height:Width).

This is particularly true of images and some shapes.

Result is 0 if this layer type does not have a preferred aspect ratio.

Typical results:

Portrait image: 0.67

Landscape image: 1.33

Star shape: 1

Text box: 0 (i.e. no preferred ratio)