[OSM-dev] What about sharing basic rendering rules and using SLD?

[Andy Allan]

On Mon, Jun 2, 2008 at 10:50 AM, Sven Laudel <s.laudel at googlemail.com> wrote:
> Andy Allan schrieb:
>>
>> So, as a cartographer, I can say "I want all station symbols drawn at
>> the expense of parking symbols" and control that through the rendering
>> rules, by putting the station symbols first.
>>
>
> So does this mean, the osm.xml file is evaluated bottom up? Or is it top
> down?

It is in the order that you read it, within each level of ordering. So
the first layer is drawn first, then the second etc. Within a style,
the first rule that is matches is drawn first, then the next. Within a
rule, the first linesymbolizer is drawn first, then the second.

But remember the mapnik has collision detection (osmarender doesn't,
AFAIK), so if you draw all the station icons first, then the parking
symbols won't draw over the top of them.

If there was no collision detection, you would draw the important
things last in order to be over the top of everything else - but then
you'd be wasting one of the best features of mapnik!

Cheers,
Andy