[Mapcss] Layering model enhancements

[Thomas Davie]

On 16 Apr 2011, at 13:09, Komяpa wrote:

> Hi everyone,
> 
> Thinking of casings/polygons problem.
> 
> Imagine a linear road that finishes as asphalted surface inside a
> forest. Let the road be highway=service; the asphalted surface -
> highway=service area=yes, and forest - landuse=forest.
> 
> Currently, we draw:
> - forest as green;
> - highway=service area=yes polygon as white
> - casings for both highways. The casing for linear service overlaps
> with white area's polygon.
> - linear fill for highway.
> 
> That leads to rendering artifacts. We can omit them by rendering first
> casings, then polygons - but that leads to roads being casingsless in
> forests.
> 
> What I propose:
> - add background-*, same as fill-*, rendered before casings;
> - render fill-* in the same loop with lines.
> 
> Any objections / better ideas?

I'm not sure your solution is the correct one.  Instead, I propose a casing-z-index property.  This would allow you to specify that the road's casing should be drawn after the forest's fill.

Bob