Re: [RFC PATCH] Per-window face support

[Stefan Monnier]

>> Is there any chance we could allow running Elisp code there, i.e. allow
> I thought about that, but I worry that allowing arbitrary code to execute
> there would make any kind of caching invalidation or something much harder
> later.

Indeed.

>>      (:filter FUNCTION FACE-SPECIFICATION)
>> or even just
>>      (:filter FUNCTION)
>> where FUNCTION returns the FACE-SPECIFICATION (or nil, say).
> If we went this route, I'd probably want to call it :eval.

[ Based on the previous point, this might be moot, but it's a problem
  we have in many places in Elisp, so I find it's important to say it:  ]

I don't object to the name :eval BUT the argument should be a *function*
and not an *expression* (i.e. the implementation should involve
`funcall` rather than `eval`).

It's no accident that "eval" and "evil" sound so much alike.


        Stefan