[gs-bugs] [Bug 690340] New: enhancement to CIDFont emulation with TrueType fonts

bugs.ghostscript.com-bugzilla-daemon at ghostscript.com bugs.ghostscript.com-bugzilla-daemon at ghostscript.com
Thu Mar 19 08:21:25 PDT 2009


           Summary: enhancement to CIDFont emulation with TrueType fonts
           Product: Ghostscript
           Version: HEAD
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P4
         Component: Font API
        AssignedTo: support at artifex.com
        ReportedBy: ken.sharp at artifex.com
         QAContact: gs-bugs at ghostscript.com

The current CIDFont emulation using native TrueType fonts is less than optimal
with respect to CMAP tables. The problem is that the character code is mapped by
the PostScript CMap to a CID, but this has no meaning in TrueType. We tackle
this by converting the CID to a Unicode code point (via the UCS2 CMaps ?) which
we then pass through the Font's own Unicode CMAP tbale to produce a glyph ID.

At present we create a dictionary called TT_cmap from the TrueType font's CMAP
table (preferring a 3,0 Unicode subtable). We then use this in a call to
.fillCIDMap in order to build a 'GIDmap'. which we use to convert CIDs via
Unicode code points to a TrueType GID (glyph ID).

We try to use similar code in the FAPI module to perform the same task, but
because the font client is handling the font, we haven't copied the CMAP table
and so the code fails (see issue #689826).

I'm in the process of adding work-around code to the FAPI to handle this for
FreeType, but in the long run it would be nice to do away with holding the
TT_cmap dictionary altogether. If we could rationalise the code so that it works
with the FAPI clients and our own code at the same time that would be ideal.

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