[mkgmap-dev] Line direction flag, merging etc

Mon May 17 11:29:28 BST 2021

Hi Gerd and others

I'm starting a dedicated thread as previous posts are split between
various svn commits.

Looking at the current trunk code and ignore-oneway-for-lines.patch,
there are bits I don't understand or didn't expect.

This is what I hope for:

--line-types-with-direction lists the lineTypes for which the initial
state of the hasDirection flag is considered true. It should be
independent of --allow-reverse-merge (see later). The purpose of this
is to reduce the need to edit styles and clarity as to which lineTypes
are displayed with direction. 

In the following, road means line with [road_class, road_speed], so
includes ferries.

Style processing, having produced a line/road, sets hasDirection, in
order of precedence:
1/ value of mkgmap:has-direction if tag exists
2/ true if oneway road
3/ true if in line-types-with-direction list

RoadMerger merges roads with same lineType, names, class, speed, oneway
and hasDirection. It must not reverse oneway or hasDirection=true roads
when doing this.

I don't think we need --allow-reverse-merge.

LineMergeFilter operates for level > 0. It merges any line/road with
the same lineType, names, hasDirection. It must not reverse
hasDirection=true.

Ticker