Copyright 2007 TeX Users Group.
You may freely use, modify and/or distribute this file.

===============================================================================
Adding extra f-ligatures to a `base' font from `expert' companion makeexptr.txt
===============================================================================

Some fonts (like Lucida Bright and Lucida Sans) have all five f-ligatures
(ff, fi, fl, ffi, ffl).  Most plain vanilla text fonts only have the two
basic f-ligatures (fi and fl).  In some cases companion `expert' fonts do
contain the extra f-ligatures.  This short note explains how to use utilities
in the Font Manipulation Package (and a plain text editor) to copy these
into the `base' font.

This is a sample protocol to add `ff', `ffi', `ffl' ligatures to a `regular'
font from a companion `expert' font.  The example here is for Adobe Garamond
Regular.  Just substitute the file names of the regular (base) font and the
`expert' font for `gdrg' and `gerg' respectively.

We start with the outline font files and corresponding metric files:

	gdrg____.pfb (Adobe Garamond Regular PFB file)
	gdrg____.afm (Adobe Garamond Regular AFM file)

	gerg____.pfb (Adobe Garamond Regular Expert PFB file)
	gerg____.afm (Adobe Garamond Regular Expert AFM file)

First we build the modified and merged outline font file (PFB) itself.
Make a file called `ligature.chr' with three lines containing ff, ffi, ffl
respectively (and perhaps fi and fl, since in this case the expert font seems
to contain `fi' and `fl' ligatures which appear to be slightly different from
the regular font - see note at end).

Convert the outline font files from PFB to PFA format:

	pfbtopfa gdrg
	pfbtopfa gerg

Extract subfont with just the chosen characters in it (result in subfont.pfa)

	subfont -c=ligature gerg

Merge regular font with subfont with glyphs to be added (result in merged.pfa).

	mergepfa gdrg subfont

To avoid conflict with the original Garamond, we need to change (i) the
file name(s), (ii) the PostScript FontName, and (iii) Windows Face name.
Edit the file `merged.pfa'.  Change `Garamond' to `GaramondX' in four
places:  First line of the file, FontName, FullName, and FamilyName.

To avoid conflict with the original Garamond in glyph caches of PS
interpreter we need to also inactivate the UniqueID.  Comment out the
line `/UniqueID 37598 def' (i.e. add % at the beginning of the line).

Change the name of the file from merged.pfa to `gxrg____.pfa' say.

Convert the resulting PFA file back to PFB format:

	pfatopfb gxrg

That is it for the actual outline font file (PFB) itself.  Now we have to
make a new Windows metric file (PFM).  Start by editing the gdrg____.afm
file.  Add lines from gerg____.afm for `ff', `ffi' and `ffl' (and perhaps
`fi' and `fl' - see note at end).  Change the character code of these new
lines to -1 (meaning unencoded).  Add lines just before `EndCharMetrics'
(although it doesn't really matter).

Change `Garamond' to `GaramondX' in the afm file also (in three places:
FontName, FullName and FamilyName).

Change the name of the AFM file to  `gxrg____.afm' say.
Make a Windows metrics (PFM) file for the new font:

	afmtopfm gxrg

That is it for the new Windows metric file (PFM).  Install the resulting PFB
and PFM files using ATM (`Add' in ATM control panel)

Finally, make a TeX metric file for your chosen encoding. For example:

	afmtotfm -vadjx -c=texnansi gxrg

Copy gxrg.tfm to a directory listed in the TEXFONTS environment variable.

NOTE: if you want to use the `fi' and `fl' ligatures from the expert font ---
rather than the glyphs on the `base' font --- then you need to first remove
the corresponding glyphs from the base font before merging. Make a `subfont'
of the base font with those two characters removed.  To do this, set up a
file called `noligs.chr' say, with two lines containing ~fi and ~fl, then

	subfont -c=noligs gdrg

You have to rename the subfont.pfa files to avoid conflict when you run
subfont a second time.  Suppose you named the subfont of the expert font
`subfonte.pfa' and the subfont of the regular (base) font `subfontb.pfa' 

	mergepfa subfontb subfonte

and proceed as before.  When editing the AFM file remember to also remove the
original lines for `fi' and `fl' and copy the corresponging lines from the
expert font AFM file. 

NOTE: instead of adding lines for the new ligatures to the CharMetrics
section in the AFM file, you could run PFAtoAFM on the merged PFA file.  
This will give the correct CharMetric section, but the kern pairs will need
to be copied over from the original AFM file (since there is no kerning
information in the PFA file), and the lines *before* `StartCharMetrics'
should also be copied from the original AFM file, since they may not be 
as accurate or complete in the output from PFAtoAFM.