Postprocessor: fallback opacity

[iamvdo]

Add a fallback opacity for IE.

This

.e {
    opacity: .5;
}

has to be converted like so:

.e {
    opacity: .5;
    filter: alpha(opacity=50);
}

https://developer.mozilla.org/fr/docs/Web/CSS/opacity

[7studio]

Vincent,
I think it is a very good idea. 👍

If you didn't edit your issue last night, I would have said you that IE8 seems to support the syntax filter: alpha(opacity=XX); 😉.

IMHO, this fallback should alert users when they use the property in the wrong way. According to this interesting answer, IE8 doesn't render opacity on pseudo-elements: Why does a filter gradient on a pseudo element not work in IE8?.
That could be interesting to throw an error in the case where this use is found.

What do you think about that?

[iamvdo]

I opened this issue based on your suggestion. ;)

I don't really know if the we have to inform users about pseudo-elements/IE8 issue, I mean, not the fallback by itself... Maybe this could be a linter job?