On Mon, 2007-05-28 at 23:48 +0200, Werner LEMBERG wrote: > > [...] I believe that any OpenType Layout engine should do its own > > validation, > > Why? What is bad about letting FreeType doing that? Afterwards you > can omit any error handling...
For one thing, FreeType is not necessarily available. We are removing FreeType dependency from HarfBuzz, and Qt wants to use HarfBuzz on Windows too. The other reason is that, for example, HarfBuzz is forgiving about some problems. A nonexistent lookup index for example is automatically ignored. Or a subtable that is not ever referenced can have an (invalid) offset of zero and it will still work. These kind of exceptions were added to make fonts that already worked with Windows work with Pango too. My plan for the rewrite I'm doing is, whenever I see a problem in a table, instead of rejecting the font, or having to check for validity all the time, just modify the data in place to make it valid. That will partically defeat the idea of using mmap()ed fonts, but it's not a big deal. > Werner -- behdad http://behdad.org/ "Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." -- Benjamin Franklin, 1759 _______________________________________________ Freetype-devel mailing list Freetype-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/freetype-devel
