[PDFBOX-5603] Support GSUB LookupType 2 (Multiple Substitution Format 1)

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.0 PDFBox
• Component/s: FontBox
• Labels: gsub
• Assignee: Tilman Hausherr
• Reporter: Tilman Hausherr
• Created: 14/May/23 08:47
• Updated: 18/Aug/23 05:46
• Resolved: 11/Aug/23 15:34

Description

This table is the reverse of ligatures, i.e. replace one glyph with several glyphs. I don't know if this is useful at all for us, except understanding the current implementation.

This will be implemented in two steps. Reading these tables is one thing, actually doing anything with it is another, because MapBackedGsubData has a Map<List<Integer>, Integer> which is not useful here. Either we'd have to introduce a second map, or extend the map so that the value is also a list. I'll do just the first part for now, which I expect to stay regardless of changes for the second part.

Issue Links

• is depended upon by: PDFBOX-5648 Support GSUB LookupType 2 (Multiple Substitution Format 1), part 2