Re: [css3-text-layout] margin-before/after/start/end etc. and :ttb pseudo-classes

On Jun 4, 2010, at 2:07 PM, fantasai wrote:

> At no point in time has the Working Group seriously considered
>     a selector that keys off the value of another CSS property. *All*
>     such proposals have been rejected outright because of the kind of
>     problems Brad points out here.



The objection is :ltr/:rtl/:ttb would depend on the value of writing-direction determined for a given element in the document and similar proposals have been rejected before for good reasons.

Murata-san – I think – might be satisfied if there was a way to say 'when the user's preference is set to vertical text, the following rules apply'.

So is it reasonable to separate :ltr and :rtl to be a shorthand for inherited [dir] but to explicitly define :ttb as something entirely different? A selector whose matching solely depends on whether the user prefers this (part of?) the document to be vertical?

Quoting CSS 2 5.10: "CSS introduces the concepts of pseudo-elements and pseudo-classes to permit formatting based on information that lies outside the document tree."

Clearly it is one of the responsibilities of this group to consider first whether it is possible to reuse existing mechanisms and avoid the complexity and potential myriad interactions of a new concept. Are there serious implementation difficulties in defining :ttb to mean 'look at preferences'?

Or for that matter, someone proposed a media query... certainly one could argue a user preference for vertical layout is reasonably within that definition.

Finally, Murata-san, isn't there a need for the document author to specify 'vertical is the default' too? Should dir="ttb" be proposed for HTML 5?

AndyT (lordpixel - the cat who walks through walls)
A little bigger on the inside

	(see you later space cowboy, you can't take the sky from me)