[XeTeX] fontspec and scaling

[Mike Maxwell]

On 1/17/2015 9:08 AM, Zdenek Wagner wrote:
> Fontspec does not do any magic. It just provides human friendly
> interface to the raw commands. It is somewhere in between the raw
> commands and GUI selection. It cannot in principle emulate optical
> sizes but it has properties for selecting them if they are available
> in the font.

Thanks for the response.  I guess my question is: _If_ a font provides optical 
sizes, then presumably telling Fontspec which point size to use causes it to 
choose the optical size provided in the font (assuming one exists for the 
requested point size).  If this is correct, then to re-phrase my original 
question: If instead of specifying a point size for a particular font/stretch of 
text, I tell Fontspec to use scaling, then does it choose the closest optical 
point size provided in the font (and maybe magnify/demagnify it slightly if the 
scaling doesn't result in an exact optical point size)?  Or does Fontspec 
instead magnify/demagnify the glyphs from the document's default point size?
-- 
	Mike Maxwell
	maxwell at umiacs.umd.edu
	"My definition of an interesting universe is
	one that has the capacity to study itself."
         --Stephen Eastmond