[FOP-1349] [PATCH] ZWSP works as backspace when font is embedded

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 2.5
• Component/s: renderer/pdf
• Environment: Operating System: All; Platform: All
• External issue ID: 42109
• Assignee: fop-dev
• Reporter: Paul Vinkenoog
• Created: 12/Apr/07 16:28
• Updated: 14/Apr/07 09:32
• Resolved: 01/Apr/12 06:36

Description

When fonts are embedded in the PDF, zero-width spaces have a backspace effect:
the text following the ZWSP is left-shifted by about one character's width, so
it partly overprints the preceding text. At the end of a text area containing
ZWSPs there's extra whitespace, up to the point where the text would have ended
had it been rendered correctly.

Observed with Times, Verdana and MSMincho, but not with Courier, and only if the
font is embedded in the PDF file. It makes no difference whether the metrics
file has an entry for ZWSP (8203d) or not.

Attached are a FO and a PDF file demonstrating the effect. I also attach a patch
that intercepts non-stretchable ZWSPs before they are written to the PDF stream.
This doesn't address the cause of the problem so it's probably not the best
solution, but at least it cures the disease. And there's no point in writing
zero-dimension areas to the PDF anyway.