[mkgmap-dev] Commit 4710

Fri May 14 15:51:38 BST 2021

Hi all,

reading the discussion, I think it would be good to separate 2 cases:
- routable roads with one-way attribute,
- all lines which have direction.

As for routing, I would assume, that all problems are resolved 
automatically and correctly by mkgmap. Routing is only valid at level 0. 
On lower resolution one-way attribute can be ignored by default. I don't 
see any problems here and I hope we could drop this case.

Second case is more general an it include roads too. It is about 
preserving direction of a line to get a correct drawing on a map. This 
is dependent on a style and TYP. Basically style defines, which objects 
should preserve direction because graphics defined in TYP is not 
symmetrical. It seems obvious, that direction should be preserved at all 
levels.

Now, if we get one-way road, we have 2 option. Leave it at default and 
allow for reverse merging at lower resolution. Or we can add 
"preserve-direction" attribute, and make it behave like any other line, 
that has direction. Which means no revers merging at lower resolution.

I don't get the idea of a list of types with preserved direction. For me 
this attribute is defined in style and separate list, or even list as a 
part of style doesn't make sens. I would prefer to have all attributes 
directly in style at place, where I define object. It seems tedious to 
sync list, whenever I do a change to object in style.

@Ticker
My nuvi 3540 shows direction arrows on roads, when TYP doesn't override 
graphics. Older nuvis don't and I got no newer one to check.
I have looked more carefully and I found that arrows are present on 
railroads too. This is probably due to mkgmap processing oneway=yes for 
railroad (actually tramway). I can't see anything on rivers, but river 
is a thin line and it is difficult to tell if anything is drawn over it.

-- 
Best regards,
Andrzej