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<div class="gmail_quote">On Thu, May 14, 2009 at 11:40 PM, Sargon Hasso <span dir="ltr"><<a href="mailto:sargon.hasso@gmail.com">sargon.hasso@gmail.com</a>></span> wrote:<br>
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<div text="#000000" bgcolor="#ffffff">Gareth,<br>I don't have the Estrangelo Antioch font (I will check them after I find them), but recall I did mention that I worked on the meltho fonts. It appears that the ligature rules are not defined for lamad+alap or taw+alap. In my East Syriac Fonts, I do have them defined (see attached). <br>
You can see clearly the lamad+alap ligature (ignoring your rendered namedglyph: mine is mapped to a different glyph).<br><br>For taw+alap, in this version of the font, you might think it is not a ligature, in fact it is. This was a font that someone did not want to have a different taw+alap ligature. In East Syriac fonts, we have 3 different taw+alap ligatures. There are no rules which one should be active. Originally, we had a rule that always picked a ligature, but some people did not like that rule so we relaxed it. For those people who wanted the taw+alap rule imposed, they wanted to have an option to select among the 3 ligatures. In TTF specs, you could have have more than one alternative, but, unfortunately, Microsoft did not implement this ligature selection alternative in their rendering engine (uniscribe). So, we cheated, and created 3 different versions of the same font with obligatory taw+alap rule each with different ligature to cater to different audience. <br>
<br>The sade+nun: although you mentioned that it renders correctly, it is in fact wrong. This ligature should only renders if it falls at the end of the word. In my font, sade+nun at the beginning of a word is not ligated.<br>
In Syriac, we really don't have mandatory ligature rules (with the exception, I believe, of the lamad+alap, but this has other complications). Some people like the ligatures, others don't. Unfortunately, like I mentioned above, we don't have that option in the TTF implementation of Microsoft. If XeLaTeX can utilize that feature, I can certainly add those additional ligatures in the Syriac fonts and have the user control the selection. I will dig up my TTF specs and refresh my memory. <br>
In East Syriac: we have two other ligatures: the he+yud, and taw+yud. Again, these are optional ligatures and not all people like them. In West Syriac fonts, there some additional ligatures like: lamad+lamad+alap (it looks better with a ligature), alap+lamad, and I think few more that make the character combination aesthetically more pleasing in ligated form than their isolated form. <br>
<br>Look at the last row of this glyph table, and you will see several ligatures for taw+alap (forgive the print screen capture quality). <br><font color="#888888"><img alt="" src="cid:part1.09090907.05000103@gmail.com"><br>
<br>Sargon</font>
<div class="im"><br><br><br>Gareth Hughes wrote:
<blockquote type="cite"><pre>Estrangelo Antioch is one of the freely available Meltho fonts for
Syriac. I can see that the font has three ligature glyphs, but XeTeX is
only forming one of them, to access the others I need to make a special
glyph call. The minimal input and output are attached. When I use
Fontforge to read the lookups, the two ligatures are mentioned in
ligature substitution subtable 9 in joining and isolated forms. However,
I don't know how to get this table to be used.
Gareth.
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