Hi, 2011/7/28 Frederik Ramm <[email protected]>: >> The suggestion to "fix tilemill to support MapCSS like everyone else >> does" is laughable, really. I would certainly promote convergence in >> the syntaxes, but that's more likely to be by MapCSS tacking towards >> everyone else than the other way around. > > I guess that's the kind of skewed view one gets when one deals only with OSM > software - after all, recent months have seen MapCSS used in all major OSM > editors, a JavaScript based rendering engine, an Android map client...
It's rather hard to fully support MapCSS in Mapnik - it has been made by people sick of some mapnik's limitations :) The "simple way to make MapCSS renderer" is different from what we've got in mapnik, so when trying to make converters from mapcss to mapnik, you've got to chose the hard ways. For instance, in Komap, I had to skip "cascading" part of MapCSS - single statement in stylesheet becomes a number of symbolizers (up to ~15 for now). MapCSS-based renderers and Mapnik-like ones have different ideology of rendering: in mapnik, you: - take out of database these things; - render with this rules, in order they come from db; - repeat with other query and rules. in mapcss-like renderers, - take out of database everything you need, or a bit more if it's easier; - map a style to each of the elements from database; - sort them by z-index property; - render each elements with applied stylesheet. Mapnik's approach is more memory-effective, and is good enough for most GIS data (without all those layer= tags and such things that are hell to handle in mapnik really correct). MapCSS-like approach is good for OSM specifically, as it is in fact just a set of human-recognized tags mapped into a set of machine-readable tags. I think MapCSS can be also used for defining routing engine rules, and probably for defining transformations between OSM tags and mapping standards/shapefiles used by others. MapCSS can easily be used in mapnik-like way, just add different subpart names to different rules. And it's not that easy to make cascading work in mapnik-like renderers. Personally, I wish there was mapcss-enabled (even in limited way, like Komap) version of tilemill - then probably I won't have to continue development of user interface with map style editor and switch to some more interesting things, like realigning imagery with traces :) -- Darafei "Komяpa" Praliaskouski OSM BY Team xmpp:[email protected] mailto:[email protected] _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
