Philippe Verdy <[email protected]> wrote:
The computing order of features should not then be: - BiDi algorithm for reordering grapheme clusters - font search and font fallback (using cmap) - GSUB (lookups of ligatures or discretionary glyph variants) - GPOS
but really:
- font lookup and font fallback (using cmap) - GSUB (lookups of ligatures or discretionary glyph variants) - BiDi algorithm for reordering glyphs representing the grapheme clusters or ligatured grapheme clusters - GPOS
I can see the advantages of such an approach -- performing GSUB prior to BiDi would enable cross-directional contextual substitutions, which are currently impossible -- but the existing model in which BiDi is applied to characters *not glyphs* isn't likely to change. Switching from processing GSUB lookups in logical order rather than reading order would break too many things.
JH -- Tiro Typeworks www.tiro.com Gulf Islands, BC [email protected] The criminologist's definition of 'public order crimes' comes perilously close to the historian's description of 'working-class leisure-time activity.' - Sidney Harring, _Policing a Class Society_
