[Mapcss] Layering model enhancements

[Komяpa]

> E.g. turning circles in Mapnik require rendering an icon - the turning
> circle casing - below the highway line. Then the turning circle fill
> comes on top. This is not possible, if you draw lines in a first pass
> and icons in a second pass.

There was an idea to support rendering nodes with line styles, just of
horizontal zero length.
Then it comes: linecap:round makes a circle, linecap:square makes a
square, width: defines size of the icon and so on.
Mapnik's turning circles go well with this concept. Any other ideas
for what you will need icons under ways?

> In MapCSS, you have to assign explicit z-index and in addition have a
> reasonable order for casing, text, etc. I'm not sure if background-* is
> the ultimate answer for all these issues, but it might solve the problem
> at hand. For better backwards compatibility, I'd keep fill-color and add
> an additional property, like
>
> fill-elevation: background;

This is probably a better solution, yes. "elevation" sounds not that
good for me, any other ideas?

-- 
Darafei "Komяpa" Praliaskouski
OSM BY Team
xmpp:me at komzpa.net mailto:me at komzpa.net