JEP 253 webrev ready for review

[Michael Ennen]

I am trying to mentally digest the CSS API, but I am having trouble
answering the question of whether or not the following scenario is now
possible (using only public APIs). Imagine one wanted to create a new class
that was analogous to DeriveColorConverter.java, and that it worked "all
the way down" in terms of being parsed from CSS into a
StyleableProperty<Color>. For concreteness, say one wanted to implement a
fadein function:

fadein
fadein( <color> , <number>% )

The fadein function takes a color and computes a more opaque version of
that color.
The second parameter is the opacity, ranging from 0% to 100%. Has no effect
on
fully opaque colors.

Does the API allow for a way to hook this new function up into the CSS
parser? If one implemented FadeInColorConverter extends
StyleConverter<ParsedValue[], Color> that worked according to the above
specs, how would one hook this fadein function into the parser, so that one
can write CSS such as:

my-awesome-color: fadein(my-semi-transparent-color, 30%);

and have a StyleableObjectProperty<Color> come out the other side?

If this is possible using the new APIs, then this makes those APIs very
powerful in terms of the possibilities of extending the built-in CSS
capabilities in very powerful and interesting ways. If it is not possible,
would it be feasible to make it so in the scope of this JEP?

Thanks very much,
-- 
Michael Ennen