[css-color] What to do if there's no valid fallback?

[tabatkins]

The current spec doesn't define what color to resolve color() to when all the options cause fallback. For example, what do you get from color(nonsense-colorspace .1 .2 .3)?

I think the only two reasonable options are opaque black, or transparent black. Given that the opacity defaults to 100% if omitted, I'm leaning toward opaque black.

On the other hand, we default to "transparent" in similar cases, like image(), which represents a transparent image with no intrinsic dimensions if all the alternatives are invalid, exactly as if you'd put image("nonsense", transparent). This might be explainable by the different assumed contexts - most elements don't have background images so defaulting to invisible is fine, but most colors are used to make things visible so defaulting to an opaque color is better.

[svgeesus]

I agree there should be a defined fallback and that black is the obvious one. On balance, I like the opaque black better - if it is an authoring mistake, it is easily spotted and corrected by them. Invisible ink is just mysterious to the author trying to debug their stylesheet..

[tabatkins]

k, i used opaque black

[frivoal]

I don't know if it would be the right answer, but I think there are more alternatives to consider than black and transparent black.

What about using currentColor? This might not be a great fallback when used as a background color, but neither is black, and when used as a foreground color, it might end up being useful more often than black is.

[Crissov]

I believe @frivoal is right, currentcolor would be the desired fallback for foreground properties like color and border-color, but transparent would be more appropriate for background-color etc. Using black (or white or transparent) everywhere would be harmful in more cases. What you really want is something like partial inherit or default.

[frivoal]

Maybe we want to define something like current-background-color. In general, that'd be useful. and if we had that, maybe the fallback of color() should be context sensitive, be either currentColor or current-background-color depending on the property it's used it. Or maybe that's overkill, I'm not sure.