@artix: I've slightly extended the MapStructure article to also contain a few more details on using styling+caching in conjunction, which is something that Philosopher worked out last year using pretty fancy Nasal code - this is one of these things that is really useful but not yet widely used in many layers (refer to VOR.symbol and DME.symbol for examples), but it can greatly improve performance and flexibility of your layers, because many layers can simplify their symbols to textured quads instead of having dozens of OpenVG-drawn symbols (which used to be the case in the original ND code).
Even the Avidyne Entegra R9 developers ended up copying this method due to its superior performance.
To learn more about the reasons for doing this, see: http://wiki.flightgear.org/Canvas_MapStructure#Symbols
To learn how to create layers with styling + caching support, see: http://wiki.flightgear.org/Canvas_MapSt ... ymbolCache
Let us know if you have any questions or need help - I'm sure Philosopher will also check back here (or the wiki) and respond to any open questions you may have.