[XeTeX] XeTeX and microtype-package…

[Michael Lynch]

Dear Jess,

OpenType fonts (and possibly AAT fonts too) allow the inclusion of 
different features. One of these is an optical bounds table which can be 
included as part of OpenType fonts by the developer (see 
http://www.microsoft.com/OpenType/otspec/features_ko.htm#opbd), which 
would describe for individual glyphs how far they should protrude to 
achieve proper optical margins. Currently, I believe very few fonts 
(possibly none!) support this feature. Certainly, none of the fonts I 
have seem to have these tables.

The second half of the problem is that the layout engine needs to 
support this feature. XeTeX does not currently allow for this, and as I 
understand, there is no simple way to port the code used in pdfTeX due 
to the different internals of XeTeX. I've seen mention that LuaTeX will 
support this feature and the micro-typographic features currently 
available in pdfTeX, but I'm not sure what it'll do when fonts don't 
contain the required features.

(At the moment, pdfTeX with the microtype package is in the advantageous 
position that typically, a relatively small set of fonts are used. It 
comes with settings for a basic set of fonts (see 
http://www.tex.ac.uk/tex-archive/macros/latex/contrib/microtype/microtype.pdf, 
page 21), and if other fonts are used, I think generic values are used 
instead. I don't think this would be a reasonable option for XeTeX given 
the variety of fonts often used.
The only other program that I know of that supports optical margins is 
Adobe InDesign (excepting the hz-program, which I don't think is widely 
available). Looking at it, it clearly implements them somehow, but since 
the tables don't exist in fonts I don't know what it does. By way of 
pure speculation, it may also use generic values or possibly try to 
calculate its own values for the optical bounds from the glyphs 
themselves. I don't even know if it uses the correct values if the font 
happens to provide them, but I guess that at least could be tested 
relatively easily.)

I'm afraid none of this is very much help for you. Unfortunately the 
feature you want is not currently supported by XeTeX, and even if it was 
added to tomorrow, most fonts don't support it anyway. Sorry for the 
rather long response but I hope this clears it up at least.

Regards,

Mike

(If you have the expertise to add it, from previous responses on the 
list, I think you'd make a lot of people happy! We'd also need some sort 
of mechanism to specify a mechanism where these values could be 
specified separately. This would rather complicate the situation, but 
given that not all fonts' licenses allow modifications to be made, I 
think it's the only reasonable way to make it work. Even if these 
modifications were allowed, it would make documents dramatically less 
portable, as they would depend on locally modified fonts with the added 
opbd tables, rather than just specifying extra settings which made it 
clear that these were additional features.)

On 02/01/2010 08:04, jezZiFeR wrote:
> Dear Pete,
>
> thank you. The reason why I want to use micro-typography is because I 
> want to have the margins aligned. I especially don´t like the hyphens 
> inside of the text. You mentioned the »opbd table« which would allow 
> optical alignment – is it the optical alignment of the outer margin, 
> which is meant? What is »opbd table«, and how could I use it?
>
> Thanks again, best
> Jess
>
>
>
>
>
>
>
> Am 01.01.2010 um 23:25 schrieb Peter Dyballa:
>
>>
>> Am 01.01.2010 um 22:18 schrieb jezZiFeR:
>>
>>> Is there any solution to this?
>>
>> Somewhen in this millennium, presumingly earlier.
>>
>>> Are there any more information on this topic?
>>
>>
>> Yes, there might be a dozen threads on this topic in XeTeX mailings 
>> archive, I think here: http://tug.org/mailman/listinfo/xetex. XeTeX 
>> uses features built into the font while the microtype package uses 
>> some "external" information. Almost a year ago, in February, Adam 
>> Twardowsky mentioned the opbd table, which, if implemented, would 
>> allow font protrusion and the rand table "optical/grey value alignment."
>>
>>
>> Why would you like to use XeTeX with micro-typography?
>>
>> -- 
>> Greetings
>>
>> Pete
>>
>> There are very few jobs that actually require a penis or vagina. All 
>> other jobs should be open to everybody.
>>                 – Florynce Kennedy
>>
>>
>>
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