[mkgmap-dev] [Patch v3] drive-on-left/drive-on-right handling

Tue Dec 2 10:00:14 GMT 2014

Hi all,

attached is v3 of the patch. I think we should finish this before 
we start with the coding for the non-rectangular tiles support.

1) I've tried to make sure that the flags in TRE and NOD are set to equal values.

2) The options --drive-on-left and --drive-on-right are deprecated but still
evaluated, for now a warning is printed when they are used.
The new option --drive-on=detect|right|left should be used instead.
The value detect enables a rather complex (but not CPU-intensive) algo:
1) For each roundabout it checks if the country is known and -- if so -- if the country 
is a drive-on-left country. 
2) If the number of "dol" roundabouts is larger than the rest, the internal drive-on switch is
set to "left", similar the internal drive-on switch is set to "right" if the number of "dor" roundabouts is 
larger than the rest.
This works only if either a complete bounds file is used or the default country is set with 
--country-abbr or --country-name.
3) If option --check-roundabouts is used and the internal drive-on switch is still "detect",
than the first found roundabout is used to set the internal drive--on switch.
4) Finally, If the internal drive-on switch is "left", the flags in the headers  are set to 1.
5) The polish fomat reader now recognizes the line
LeftSideTraffic=Y
in the mp file.
6) If the user specifies --drive-on=left, both header flags are set to 1, no matter what 
roundabouts are found.

@Steve, WanMil:
I've added a ThreadLocal<boolean> to TREHeader similar to that in NODHeader,
but I think it would be better to store that info only once for each thread,
I just don't know where, maybe MapMaker?
Besides that I am not sure how this works when we write two different TREHeader files
in one thread (one for the overview map data ovm_*.img)
(well, the flag in these files is ignored anyway)
Please suggest a better solution.

Gerd

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