[Mapcss] Making it approachable

Richard Fairhurst richard at systemeD.net
Mon Feb 7 18:11:25 GMT 2011

Thomas Davie wrote:
> I don't really see how the layers proposal would change the above
> example (or any simple example), with a good quality default style
> sheet (that maps layers into z-indexes nicely).

Because the task has suddenly jumped from "newbie, just write some stuff 
that looks like the CSS you already know!" to "newbie, you've got to 
copy-and-paste this stuff in order for things to work as they should. 
Don't worry that you don't understand it".

If any renderer wants to internally take that approach for its layer 
support, that's cool: MapCSS doesn't dictate how your renderer's 
internals should work. And if you can think of a clever way of 
facilitating overrides, that's cool too. But not at the cost of adding 
an extra hurdle for newbie stylesheet writers.

 > A practical example to justify why this is something we'd want: when
 > selecting ways in an editor it would be useful to make those ways
 > appear on top of un-selected ways, with highlit casings (Potlatch
 > does exactly this in fact).

P2 does it [1] simply by saying
	way :selected { layer: 5; }
and I would commend that approach to the house. :)


[1] Actually, it doesn't: only the nodes in the selected way appear on 
top, the way doesn't. But if we did want the way to appear on top, 
that'd be how we did it.

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