bug#22923: [PATCH] Support completion of attribute values in CSS mode

[Dmitry Gutov <dgutov@yandex.ru>]

Hi again, Simen,

On 03/19/2016 02:42 PM, Simen Heggestøyl wrote:

> Yes, it allows us to stay close to the CSS spec, which is my view is
> very valuable when maintaining these lists.

Sure, but by "current approach" I meant what Company does. Please clarify:

> Here is a concrete example: the value class `image' is defined as
> follows in the CSS Image Values spec [1]:
>
>   <image> = <url> | <image-list> | <element-reference> | <gradient>
>
> Which translates naturally to:
>
>   ("image" uri image-list element-reference gradient)
>
> It is not a CSS property, so it should go into the value class alist. It
> is referenced by the `border-image-source' property as well as the
> `bg-image' value class (which in turn is referenced by the
> `background-image' property and `bg-layer' value class).

If you were adding it to company-css, wouldn't you just add it to 
company-css-value-classes? And then refer to it in background-image 
value inside company-css-property-alist?

What the limitation of that approach? Do value classes in the spec refer 
back to the actual properties sometimes?

> My point is that even though it would be possible to eliminate the need
> for this value class by expanding it where it is referenced, I think
> that by keeping it, it'll be much easier to make updates to it when the
> CSS spec changes. I think it is worth the added complexity.

I'm not sure I follow. Expanding it in company-css-property-alist?