[FOP-2938] Incomplete TTF subset files for mutibyte fonts - incomplete mapping between CIDs and codepoints when having two codepoints associated to the same glyph

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.5
• Component/s: font/opentype
• Assignee: Unassigned
• Reporter: Dan Caprioara
• Created: 18/May/20 08:56
• Updated: 21/Apr/22 10:59

Description

A generic problem appears for MultiByte CID fonts.

Because of a limitation of the CIDSubset implemenatation, once a glyph has been used for a code point, next usages of the same glyph for other codepoints are discarded. This results in incomplete tables in the TTF sub set file. The structures from CIDSubset class are maps, limiting expressiveness.

 

In the next diagram I used hyphens and soft hyphens, just as an example, any text with two different characters that map to the same glyph is affected.

See this attached sketch for details:

The solution would be to avoid usage of hash maps, and create some associative lists (currently the uniqueness of the keys breaks things).