RE: [css3-2d-transforms][css3-images] <position> grammar is duplicated or points to the wrong spec

Tab:
> Your proposal for <complex-anchor> appears to roughly the same as what
> I'm suggesting, except that it additionally allows a bare
> "background-position: 50% + 5px;", and it still makes

My proposal doesn't say that.  That's one incarnation you *could* specify in the (new) 4th and 5th clauses.

Some simple variations could be...
	Background-position: complex-anchor(50% + 5px);
	Background-position: (50% + 5px);


Brian:
> The following approach is significantly better:
> 1. Backgrounds: Introduce <complex-anchor>
>	<complex-anchor> = <percentage> [+ | -] <length>
> 2. Backgrounds: Introduce 4th (and maybe 5th) clause(s) to <bg-position> that show when <complex-anchor>
> can be used.  Note that it's probably desirable to only > support this in background-position not anywhere else
> that <position> is now being used.
> 3. Backgrounds: Define how <complex-anchor> behaves when used within a background-position value
> 4. Values: Describe how "calc(<complex-anchor>)" resolves to "<complex-anchor>" when found within
> background-position values
> Result:  Backgrounds module remains the definitive authority on how background-position behaves and there is no ambiguity.

Tab:
> "background-position: 50%" and "background-position: calc(50%)"
> resolve to different values (I think).

If you only did steps 1-3, yes.  If you also do step 4, no.