[XeTeX] The future of XeTeX

[Joel C. Salomon]

On Mon, Jul 30, 2012 at 5:12 PM, Philip TAYLOR <P.Taylor at rhul.ac.uk> wrote:
> I have held back from experimenting with LuaTeX because I have
> been led to believe, from this list and elsewhere, that LuaTeX
> and XeTeX are not in 1:1 correspondence in terms of the syntax
> and semantics of some non-Lua-related features.  Are you able
> to comment on this from a position of knowledge ?  Or, from the
> converse perspective, would you be able to assure me and others
> that all extant XeTeX code will execute in LuaTeX without error
> and produce a PDF that is visually indistinguishable from the
> PDF that XeTeX would produce using the same source ?

I know for a fact that LuaTeX enables features of OpenType Math fonts
that XeTeX does not. See, e.g.,
<https://github.com/wspr/unicode-math/issues/40>.

And, of course, there are XeTeX-specific features (most prominently
interchartoks) which LuaTeX does not implement.

Avoiding math and engine-specific extensions, I personally have not
*noticed* any differences between the outputs, but given the
differences that exist I doubt anyone would care to guarantee
identical results.

--Joel