[josm-dev] Combining mappaint styles

[Dirk Stöcker]

On Wed, 27 Aug 2008, Petr Nejedly wrote:

>>> My first thought was to use something like a specially dashed (dotted,
>>> ...) way, but that would be hard to distinguish from other dashed stuff
>>> (like tracks) and also probably hard to "visually get" for very short
>>> bridges (tunnels).
>>
>> What about alpha shaded lines? E.g. if you overlap a street with a 20%
>> black line for tunnel or 20% green for bridge or something like that.
>>
>>> Obviously, I haven't tried this out, so the best would be to have a
>>> prototype and have a look at it :-)
>>
>> Well, the design of the XML and the implementation depends a lot on the
>> fact how to display it later.
>
> In josm-ng, I'm experimenting with multistyle, where each tag can add
> a (list of) stroke(s) (painting primitives) to apply, and all the tags
> are processed for given primitive (not ony the first one that matches).

I thought about something like that too.

Ok, what about that suggestion:

- Using an additional type <lineover>, which equals line, but also has an
   alpha value.
- Drawing is done as it is now, but when over's are found, they get
   applied also. Supporting multiple over's is required.
- The over's are drawn over the basic line segment (so in general they
   should have alpha below 50).
- We add optional priority="number" to the element rules to define
   which one should be used in case of matches compared to the pure
   alphabetic matching as now.
   Used numbers should be 10000 for the start (so we always have the
   chance to go a level down and move something inbetween - learned from
   basic, where it was always a bad idea to number 1, 2, 3 ... :-)

So the general idea is to have main line styles as we have now and 
overlays. Drawing areas and icons does not change except the priority can 
be used there too.

Ciao
-- 
http://www.dstoecker.eu/ (PGP key available)