[XeTeX] Syriac in Polyglossia

[Gareth Hughes]

François Charette wrote:
> 
>> I can't manage to get numerals=eastern or abjadsyriac to work. 
> The option numerals=eastern affects the numerals generated from counters 
> (pagination, footnotes, etc.) To display 2008 in Syriac according to the 
> above option, you need to type \syriacnumber{2008}. I agree that this is 
> not very clear in the documentation. I'll improve that! For abjadsyriac 
> see below. But if you want the numbers 0123456789 to appear 
> automatically as ٠١٢٣٤٥٦٧٨٩ you can define \syriacfont as follows:
> 
> \newfontfamily\syriacfont[Script=Syriac,Mapping=arabicdigits]{Estrangelo 
> Edessa}
> 
> I know, this is undocumented. Should this occur by default? Some 
> rendering engines (e.g. Pango) appear to do that substitution 
> automatically with Syriac. I should look further into this.

This is really helpful to know. What the default should be is difficult 
to say. I think western numerals will be the better default as most 
modern writers would prefer to write numbers that way. If I'm 
reproducing classical texts, I would use abjad numerals. I'm looking at 
a large volume of classical Syriac poetry printed in Mosul in 1905, and 
it uses abjad numerals throughout, for page numbering too. However, 
there are still plenty of writers who'll want to use eastern numerals, 
especially for rendering garshuni.

>>  there doesn't seem to be documentation on how to use Polyglossia with 
>> Fontspec: that is, how to name font declarations so that Polyglossia 
>> can read them.
>>   
> In your example below you did it correctly.
> 
> In general, it works as this: if for language lingua one defines 
> \linguafont with \newfontfamily, then this font is automatically chosen 
> for that language. If it is undefined, polyglossia checks in the current 
> font for the availability of the relevant script and/or language (via 
> OpenType tags) and makes the appropriate switch with \addfontfeature. 
> Otherwise an error message is displayed.

It's good to know exactly how polyglossia goes about picking its font. 
How does this work if one has a number of fonts that could be used; does 
polyglossia just choose the main font if that works, or first/last other 
to be declared that fits the bill?

> According to my sources the maximal abjad number in Syriac is 499: if 
> you look at your log file you'll notice that polyglossia issued a 
> warning about 2008 being too large. However, if you know how to 
> represent numbers larger than 499, I would be grateful to have the 
> information!

No, Syriac abjads are not limited to 499 (taw+sadhe+teth). The largest 
unmodified numeral, taw, is 400, but the letters can be combined for 
higher values. Some people would write taw+qoph (400+100) for 500, but 
the classical system places a dot (possibly U+0741) over nun (50) to 
increase its value tenfold. This system can then represent numbers to 
999 (sadhe+sadhe+teth), then 1000 is represented by alaph with a 
diagonal stroke (U+0748) below it (and beth for 2000 and so forth). In 
practice, these dots and strokes are omitted as a small value before a 
large has to be modified to make sense. Thus, 2008 is often written 
beth+heth without any modifying marks; anyone knowing the system will 
know that the beth has to stand for 2000 rather than 2. To complicate 
things, so very old manuscripts use a variant of the old Aramaic numerals.

Thanks for the pointers,

Gareth.