This is related to Fonts for PolyTonic Greek. That post contains (supposedly) working example using the names of many fonts, and each font name contains a space. Names include: "CMU Serif", "EB Garamond", "GFS Artemisia". The post states that the fonts are all part of TeXLive 2013. I have a TeXLive updated 2013 distribution. I copied the code exactly and attempted to xelatex it. But it returned an error stating that a font cannot have a space in its name. How did the previous poster manage to run code in which all font names contain spaces?
fontspec
uses the name of the font as it would appear, e.g. in a regular application on your machine. This will typically include spaces. If you are requesting a font by filename, (which you must with XeTeX with fonts in yourtexmf
directories) it cannot contain spaces.texmf
directories are typically also made system fonts. At least, a lot of Linux distros do this if you install using their packages, and it is very easy to do this yourself if you use upstream's installer. I don't know, however, whether this works on Mac OS X or Windows. Perhaps that is what @AlanMunn is thinking of?