[csswg-drafts] [css-position-3] Circular definition of fixed positioning containing block (#5332)

zjopy has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-position-3] Circular definition of fixed positioning containing block ==
(For simplicity, I'll assume continuous media below.)

The definition of the fixed positioning containing block in [css-position-3](https://drafts.csswg.org/css-position-3/#fixed-positioning-containing-block) reads

> If no ancestor establishes [an fixed positioning containing block], the fixed positioning containing block is [...] the viewport.

This definition is circular. You can't define "fixed positioning containing block" assuming the existence of it in the preceeding condition "If no ancestor establishes [an fixed positioning containing block]".

This contradicts the definition above, which [says](https://drafts.csswg.org/css-position-3/#valdef-position-fixed)

> [...] a fixed positioning containing block (the viewport in continuous media, or the page area in paged media)

IMO the term "fixed positioning containing block" is a needless complication for defining the containing block of fixed positioned elements. The containing block for fixed positioned elements should be defined directly as viewport, instead of as "fixed positioning containing block" which is then defined as viewport. It introduces an additional term that just complicates the definition. Further, this term contains the very words that you are trying to define - "containing block" - which is either a logical error or at least bad practice.

It's as if you define the word "car" as "an object with a car door" and then leave out the definition of "car door".

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/5332 using your GitHub account

Received on Thursday, 16 July 2020 10:38:22 UTC