From: Richard Wordingham (firstname.lastname@example.org)
Date: Mon Aug 22 2005 - 21:11:18 CDT
John Hudson wrote:
> In the OpenType model re-ordering is specifically NOT handled at the glyph
> level, but at the character level. This is why it only works with standard
> Unicode characters, and not codepoints in what I've come to regard as the
> 'Pretty Useless Area'.
Do you mean 'OpenType' or something like 'Uniscribe/OpenType' or
'Microsoft'? For example, the OpenType Layout page (
http://www.microsoft.com/typography/otspec/TTOCHAP1.htm ) says:
'A text-processing client follows a standard process to convert the string
of characters entered by a user into positioned glyphs. To produce text with
OpenType Layout fonts:
'1. Using the cmap table in the font, the client converts the character
codes into a string of glyph indices.
'2. Using information in the GSUB table, the client modifies the resulting
string, substituting positional or vertical glyphs, ligatures, or other
alternatives as appropriate.
There's no mention of re-ordering by Uniscribe (or equivalent) or of
breaking into runs by script - Step 0!. You have to read higher level
documentation to realise that the characters may be re-ordered (or even
changed!) before the font tables can affect them. (The separation between
Steps 0 and 1 is not as clean as I imply.)
This archive was generated by hypermail 2.1.5 : Mon Aug 22 2005 - 21:12:13 CDT