- From: Bert Bos <bert@w3.org>
- Date: Thu, 21 Jan 2010 17:11:58 +0100
- To: public-webapps@w3.org, "www-style@w3.org" <www-style@w3.org>
On Wednesday 20 January 2010, Andrew Fedoniouk wrote: > Daniel Glazman wrote: > > I would recommend dropping the pseudo-class :scope and make a > > simpler model where a fictional :scope pseudo-class and a > > descendant combinator are prepended to all selectors passed as the > > argument of the corresponding APIs. > > There are cases where you will need to match only immediate children > using such queryScopedSelector() function. > > Possible solutions: > > element.$("> .child"); > element.$(":root > .child"); > > :root here is the element itself - root of the lookup. > > BTW: the name of the function queryScopedSelectorAll() has at least > one technical and one grammatical error. Can we rename it somehow? If I read the WD correctly, not only ':scope' is redundant, but queryScopedSelector() and queryScopedSelectorAll() are, too. So I'd suggest: 1) Drop the keyword ':scope'. - It's redundant. The spec says that everywhere you are allowed to use it, you can also omit it and it will be implied. So why not omit it? - It's confusing. You are not allowed to use it everywhere, so it is an opportunity to make mistakes. - It makes the syntax that querySelector() accepts almost the same but not quite as the selectors syntax that CSS allows. Better to either have a completely different syntax or one that is exactly the same, otherwise you just invite errors. 2) Drop queryScopedSelector() and queryScopedSelectorAll(). It is trivially easy to replace a call to queryScopedSelector() by a call to querySelector(). All you have to do is replace e.queryScopedSelector(x) by e.ownerDocument.querySelector(x) where e is an Element. And for documents d the functions are even exactly the same: d.queryScopedSelector(x) == d.querySelector(x) for all documents d and selectors x. - Smaller API means less to implement, - less to test, - less to learn for users. - less variation in programs, - thus easier to understand other people's code. Somebody somewhere else was wondering about the selector ':root + *'. I would say it's a valid selector that just happens to never match anything, because a tree by definition has only one root. The same holds for selectors like '#foo #foo' (valid, but guaranteed to return nothing, because IDs are by definition unique), '*:first-child:even' (the first child is obviously odd, not even), and ':root:first-child' (the root is not a child of anything). Here are some examples of relations that always hold. (Assume e is an element != NULL.) e.querySelector("*") == e.querySelector(":root") e.querySelector("*") == e e.querySelector(":root + *") == NULL e.querySelector(":root:first-child") == NULL e.querySelector("* *") == e.querySelector(":root > :first-child") e.querySelector(":odd") == e.querySelector(":root > :first-child") Bert -- Bert Bos ( W 3 C ) http://www.w3.org/ http://www.w3.org/people/bos W3C/ERCIM bert@w3.org 2004 Rt des Lucioles / BP 93 +33 (0)4 92 38 76 92 06902 Sophia Antipolis Cedex, France
Received on Thursday, 21 January 2010 16:12:33 UTC