Just had a quick discussion about this in #osm – Komzpa (of Kothik and Kothik-JS fame), and RichardF (of Halcyon fame) agree that the order is undefined if z-indices are equal, and that z-indeces default to 0.
I've added a note on this to the MapCSS 0.2 page. http://wiki.openstreetmap.org/wiki/MapCSS/0.2#Rendering_Order Bob if (*ra4 != 0xffc78948) { return false; } On 27 Jan 2012, at 12:43, Peter Wendorff wrote: > Hi. > If you are right (and yes, that's possible, I can't prove the opposite), I > think this should be stated clearly in the documentation. > > On the other hand I'm not sure if this variant is really the best idea. > It leads to verbose, hard do maintain mapcss stylesheets if the developer > wants to set up a fixed rendering order, and usually at maps that's the case > for most rules, I think. > > I would change it in the wiki, but I would like to get more comments on that > from the list, so I don't change it now. > > regards (and thanks for the answer) > > Peter > > Am 27.01.2012 13:34, schrieb Thomas Davie: >> >> At least in my interpretation of MapCSS, the behaviour when two objects are >> defined to have the same z-index is undefined. The order of rendering here >> should (in my book) be effectively random. >> >> Bob >> if (*ra4 != 0xffc78948) { return false; } >> >> On 27 Jan 2012, at 12:24, Peter Wendorff wrote: >> >>> Hi. >>> I have to give a short introduction to someone who should implement a >>> mapcss renderer and looked into the docs availlable for that. >>> For that I especially looked into the sotm-eu presentation done by Maskim >>> [1], and I fear there is a small bug on slide 7 (and the following pages). >>> >>> The stylesheet presented does not contain any z-index or layer definitions. >>> To quote the slide, it's defined as: >>> >>> line[highway] { >>> color: orange; >>> width: 11; >>> } >>> >>> area[building] { >>> fill-color: gray; >>> } >>> >>> line[waterway] { >>> color: blue; >>> width:3; >>> } >>> >>> The image presented nearby shows a similar image, but the highway is >>> rendered on top of the river. >>> Shouldn't that be the other way around (according to the mapcss code, not >>> to "good maps")? >>> >>> regards >>> Peter >>> >>> [1] http://sotm-eu.org/slides/10_MaksimGurtovenko_MapCSS.pdf >>> >>> _______________________________________________ >>> Mapcss mailing list >>> [email protected] >>> http://lists.openstreetmap.org/listinfo/mapcss >> >> >> >> _______________________________________________ >> Mapcss mailing list >> [email protected] >> http://lists.openstreetmap.org/listinfo/mapcss > > _______________________________________________ > Mapcss mailing list > [email protected] > http://lists.openstreetmap.org/listinfo/mapcss
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