[xep-support] Ligature confusion (ae, etc.)

[David Nedrow]

OK, let's take a simple sample.

Given this Docbook snippet...

    <para>This is a test of the ligatures ae, &AElig;, &aelig;, &OElig;,
     &oelig;, ij, st, et, Et, ss, ng, ue, fs, fi, fj, fl, ff, ffi,  
ffl, fa,
     fe, fo, fr, fs, ft, du, fy, 'f.', 'f,', 'f-', and %0 .</para>

Note that this is a general list of ligatures and character  
combinations and I know that some may not be valid in all fonts/ 
contexts.

My Helvetica font has a ligature for small letter "ae" (Unicode U 
+00E6). However, if I define the ligature in the xep.xml file as ...

       <font-family name="Helvetica" ligatures="ae">
         <font>
           <font-data
             ttf="/Volumes/iDisk/local/fonts/TrueType/Helvetica- 
Bold.ttf"/>
         </font>

xep generates the following warning....

[warning] file:/Volumes/iDisk/local/xep-4.9-20070115/xep.xml:  
Character U+61 is not recognized as a ligature; character ignored
[warning] file:/Volumes/iDisk/local/xep-4.9-20070115/xep.xml:  
Character U+65 is not recognized as a ligature; character ignored

61 and 65 obviously refer to a and e separately.

Most of the expected ligatures (fi, fl, etc) work. ae does not get  
converted to a ligaturized presentation. ae is U+00E6 in the font.

In the reference doc, the only reference to ligatures is 2.4.1.3,  
where the doc notes...

"The characters must be a Unicode ligature codepoints." and  
"ligaturization does not work for characters that undergo contextual  
shaping"

I'm guessing ae falls into one of these two categories. Any ideas if  
I can simply type "ae" and expect it to work, or will I just need to  
use &aelig; going forward?

Also, are "Unicode ligature codepoints" an actual, defined list of  
ligatures somewhere in the Unicode spec?

-David


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