[XeTeX] OpenType-info.tex

[Jonathan Kew]

On 5 Oct 2004, at 5:35 am, Dalyoung wrote:

> Dear all,
>
> I had no problem to use recently installed OT fonts in my simple tex 
> files.
> But I got an error message when I try to see the supporting features 
> of the same OT font.
> It may be a font problem.
> But it is curious that the same font work well in some file but not in 
> another file.
>
> Here is the error message in the terminal.
>
> This is XeTeXk, Version 3.14159-2.1-0.87 (Web2C 7.5.2)
>  %&-line parsing enabled.
> entering extended mode
> (./OpenType-info.tex
> ! Cannot use \XeTeXOTcountscripts with smType Medium; not an OpenType 
> font.
> l.51 \scriptcount=\XeTeXOTcountscripts\testfont
>
> ?
>

This error message may be a bit misleading. It indicates that the font 
was loaded for layout using ATSUI rather than ICU, even though it may 
be an OpenType font. This would mean that it doesn't contain any 
OpenType Layout features; it's a "simple" font in an OT package.

Currently, here's what XeTeX does when you ask it to use a font that's 
installed in OS X. It locates the font, and looks to see if there is a 
GSUB or GPOS table present (i.e., OpenType layout features). If so, the 
ICU-based OpenType layout engine will be used, and the \XeTeXOT.... 
commands will work to query the GSUB/GPOS features present in the font.

If there are no OT layout tables (even though the font file format may 
still be OpenType), the font will be used through ATSUI; if AAT tables 
are present, they'll automatically be used, and if not, ATSUI will do 
"simple" layout without any special features. In this case, the 
\XeTeXOT.... commands will fail, as above, regardless of the font file 
format.

In other words, when XeTeX refers to an OpenType font it means 
specifically a font that has OT Layout features; it does not refer to 
the font file format. This is confusing, I agree, and I should try to 
make things clearer.

Jonathan
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