[mkgmap-dev] type/subtype of points and cities

Tue Oct 22 12:07:08 BST 2019

Hi Gerd

Here is the patch based on the current trunk

Ticker
On Tue, 2019-04-23 at 11:51 +0100, Ticker Berkin wrote:
> Hi
> 
> I think the mkgmap internal handling of types/subtypes of points is
> obscure.
> 
> In the points style file, the type code is always full, ie type << 8
> |
> subtype, but when the points are read back from the RGN file for the
> MDR processing, the representation is the same provided the subtype
> is
> not zero, otherwise it is just type! Logic then decides that if the
> value is <= 0xff it is because the subtype is zero.
> 
> It is simpler and much clearer to preserve the original
> representation.
> This also allows unambiguous use of type 0 with subtypes, and,
> possibly, city with subtypes.
> 
> It also allows the same function to be used to test a type for being
> in
> the 'city' range, regardless of the context. mkgmap wasn't consistent
> the ranges for the isCity test.
> 
> City POI are written in a different manner to the RGN file. The old
> range for this was:
>   type >= 0x0100 && type <= 0x1100
> which I've kept, except changing to: ...& type < 0x1200. A similar
> range was used for MDR5.
> 
> However, city POI are held in group 1 of MDR 9/10. This is used in
> Find
> > City 'By Name'. The old range was: type <= 0xf, where, if the
> > subtype
> was zero, type is right shifted by 8 (see above), non-zero subtypes
> messed up the testing. Now it uses the same range as above.
> 
> Actually neither of these ranges are correct for my Garmin devices.
> Find > City show nearby POI with types in the range 0x0100..0x0d1f,
> regardless of the img RGN or MDR. The eTrex Legend labels POIs in
> this
> range as {Large/Medium/Small} City/Town and points in the range
> 0x0e00..0x111f as "*".
> 
> Find > City 'by-name' returns POI if in group 1 of MDR 9/10. I find
> it
> a useful feature to have a POI that can be searched for but doesn't
> flood the list of nearby points.
> 
> Generally, non-zero subtypes for cities cause problems in the RGN
> structure and I've added a test for this to the style validation.
> 
> There is also a fix to --make-poi-index, but I can't detect any
> effect
> of this option.
> 
> This patch won't make any difference to the img output unless the
> there
> are points 0x1000, 0x1100.
> 
> If this patch is accepted, I'll do the equivalent to the img display
> system.
> 
> Regards
> Ticker
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