Sebastian Spaeth wrote:
On 2010-07-07, Richard Fairhurst wrote:
Sebastian Spaeth wrote:
[things about z-index]
Well, the z-index inheritance stuff is probably the thing I got most
wrong with the original spec. :)
Pfeww, I was doubting my sanity, so happy to hear that :). Yes, let's work it
out.
My current thinking is that we start with:
way[highway=footway]::highlight { width: 3; z-index: 2; }
way[highway=footway]::centreline { width: 2; z-index: 3; }
way[highway=footway]::centreline { color: green; }
In other words, you can define a new stroke(/fill) using the CSS
subpart (double colon) syntax.
Arrg, that is another part that I did not get and wanted to postpone to
another day (life?) :-). OK, so subparts we have. Are the names for
subparts arbitrary labels? If yes, things are much clearer again.
Here we have two strokes. One
(highlight) is width 3, z-index 2, green; the other (centreline) is
width 2, -index 3, green.
Hold on, why is highlight green? It is not defined above, right? Green
only applies to "centreline". Would that work as intended?
way[highway=footway]::highlight { width: 3; z-index: 2; }
way[highway=footway]::centreline { width: 2; z-index: 3; }
way[highway=footway] { color: green; }
Let's say we want to apply opacity 0.5 to all the ways above. Should we say
way[highway=footway] { opacity: 0.5; }
way[highway=footway]::* { opacity: 0.5; }
I'm tempted towards the latter.
I see your point, but I would lean towards the first option, I see these
as filters in a hierarchical stack that filter elements gradually out. So each
of
the bullet points below is a superset of elements to the next:
- way
- way|z12
- way|z12 [highway=footway]
- way|z12 [highway=footway][horse=yes]
- way|z12 [highway=footway][horse=yes]::centreline
Your proposal would make the second last line behave different from all
the others. It would make sense to support only __unnamed__ subparts
somehow, but that could happen with
way [highway=footway]:: {color: strawberry;}
I would agree that supporting "::*" would make sense and is very
intuitive. In the end, I am fine with both, but find your preferred
solution a bit awkward for the above reason.
It might be a good idea to stick to the css spec for the most part [1]
and introduce new syntax and semantic only where it is needed. The
canonical example for subpart is
p::first-letter {...}
which addresses the first letter of the paragraph, but you can still
style the entire paragraph (including the first letter) with
p {...}.
This would suggest to use the interpretation favoured by Sebastian Speath.
The difference here: The first letter of the paragraph is always
visible, but a highlight of a way is an optional/exceptional feature.
For simplicity, I would prefer to write
way[highway=footway] {width:3; color: orange; antialiasing:none}
way[highway=footway][bicycle=yes] {dashes: 2, 2}
way[highway=footway][bicycle=yes]::highlight {width:5; color: blue}
This should draw non-antialiased orange way for normal footway. If it
has the tag bicycle=yes, it should be dashed and have a blue highlight
(also not antialiased).
So my interpretation would be: way[highway=footway] applies to the way
element itself (whatever that is) and all its subparts (::centerline,
::highlight, ...) However, some subparts are defined as default
(::centerline) and others as optional (::highlight, ... the rest).
Optional subparts are not rendered unless they are declared. (I.e. there
exists at least one selector for them.) Each subpart can have a
different default value. (E.g. default z-index should be lower for
::highlight than for ::centerline.)
Does this make sense? Basically, I'm fine with any solution that removes
the "magic" from z-index property. This would make stacked rules (way
{...} {...}) obsolete, right?
[1] <http://www.w3.org/TR/2005/WD-css3-selectors-20051215/#pseudo-elements>
--
Sebastian
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