tds: Font file type location

 
 C.2.1 Font file type location
 -----------------------------
 
 We considered the supplier-first arrangement in use at many sites:
 
      texmf/fonts/SUPPLIER/TYPEFACE/TYPE/
 
    This improves the maintainability of the font tree, since all files
 comprising a given typeface are in one place, but unless all the
 programs that search this tree employ some form of caching, there are
 serious performance concerns.  For example, in order to find a `TFM'
 file, the simplest implementation would require TeX to search through
 all the directories that contain PK files in all modes and at all
 resolutions.
 
    In the end, a poll of developers revealed considerable resistance to
 implementing sufficient caching mechanisms, so this arrangement was
 abandoned.  The TDS arrangement allows the search tree to be restricted
 to the correct type of file, at least.  Concerns about efficiency
 remain, but there seems to be no more we can do without abandoning
 subdirectory searching entirely.
 
    We also considered segregating all font-related files strictly by
 file type, so that Metafont sources would be in a directory
 `texmf/fonts/mf', property list files in `texmf/fonts/pl', the various
 forms of Type 1 fonts separated, and so on. Although more blindly
 consistent, we felt that the drawback of more complicated path
 constructions outweighed this. The TDS merges file types (`mf' and `pl'
 under `source', `pfa' and `pfb' and `gsf' under `type1') where we felt
 this was beneficial.