On Fri, Sep 19, 2008 at 8:07 PM, Mohamed Bana wrote:
  

Hi guys,

Why doesn't this definition use the old style numerals that come with the font?
 It seems to use the latin modern font when I try to use \os.  Small caps are
working fine.

I'd like all the numbers in the document to be typeset in old style numerals
unless I tell it otherwise, btw how do I achieve the latter?
    

I didn't tell you that:

\definefontfeature
 [default]
 [script=latn,language=dflt,liga=yes,kern=yes,tlig=yes,onum=yes]

(the important setting is only "onum=yes")

The problem is that that's only a dirty trick that is not supposed to
work and might stop working in the future, so I would rather try not
to rely on it. A better interface for XeTeX typescripts (something
similar to fontspec) is missing heavily.

------------

Concerning your first problem: I have tried patching Xsans definitions with

\definefontfeature
  [oldstyle]
  [script=latn,language=dflt,liga=yes,kern=yes,tlig=yes,onum=yes]

\starttypescript[Xserif][all][name]
\definefontsynonym [DummyOldStyle]  [name:\typescripttwo]   [features=oldstyle]
%\definefontsynonym [DummyOldStyle]  [name:'\typescripttwo']
[features=oldstyle]
\definefontsynonym [OldStyle]       [DummyOldStyle]
\stoptypescript

\definetypeface[myface][rm][Xserif][Warnock Pro]
\setupbodyfont[myface, 11pt]

\starttext
{\os 123456789}
\stoptext

but I have no idea why it fails.

kpathsea: Invalid fontname `name:Warnock', contains ':'
! Font \thedefinedfont=name:Warnock not loadable: Metric (TFM) file or installe
d font not found.
<to be read again>
                   P
<argument> name:Warnock P
                         ro
\dotruefontname ... #1\endcsname *#2#3\fi \else #1
                                                  \ifx #2\empty \else *#2#3\...

\dotruefontname ... \??ff \fontclass #1\endcsname
                                                  \else \@EA \redotruefontna...

\dotruefontname ... \??ff \fontclass #1\endcsname
                                                  \else \@EA \redotruefontna...

\symbolicsizedfont ...ntname {\glyphfontfile {#3}}
                                                   at \currentfontbodyscale ...
l.32 {\os
          123456789}

The alternative fails with

kpathsea: Invalid fontname `name:Warnock Pro*oldstyle', contains ':'
! Font \thedefinedfont="name:Warnock Pro*oldstyle" at 11.0pt not loadable: Metr
ic (TFM) file or installed font not found.
<recently read> \scaledfont

\symbolicsizedfont ...ntfontbodyscale \scaledfont
                                                  \thedefinedfont
l.32 {\os
          123456789}


Mojca