[mkgmap-dev] patch to write polygons in decreasing order

Tue Nov 8 06:48:21 GMT 2016

Hi Ticker,

okay, I will try on my own later. Please review the patch:
1) log messages esp. those with log.warn. I think most are debug messages ? 
This one looks wrong to me:  ""Area single pixel shifted so can't split at
"....
What does it mean?
2) Comments / javadoc : Please remove commented code and add javadoc without
jokes like
@return An area containing xsplit*ysplit areas (hopefully).
Instead try to explain in what case the result will be null. 
BTW: It seems that this change in the code no longer depends on the new
option. 
Is that intended?

Gerd

Ticker Berkin wrote
> Hi Gerd
> 
> I've been looking at ShapeSplitter and clipping to a rectangle
> algorithms generally. I don't feel I know enough about how to use the
> java.awt.geom package to implement this effectively, and so I'd rather
> keep to using Java2DConverter and .intersect(), even though it is most
> likely much less efficient.
> 
> Ticker
> 
> On Sat, 2016-11-05 at 23:33 -0700, Gerd Petermann wrote:
>> Hi Ticker,
>> 
>> Gerd Petermann wrote
>> > Alternative would be to implement a clipper which doesn't need
>> > area.intersect(). I've once coded the "Sutherland-Hodgman
>> > algorithm" but
>> > ways or concave shapes producing spikes, but I still think this
>> > would be a
>> > great improvement. See attached (out-aged) patch and the wiki
>> > https://en.wikipedia.org/wiki/Sutherland%E2%80%93Hodgman_algorithm
>> > for further details.
>> 
>> I just noticed that the algo is already used in
>> ShapeSplitter.clipSinglePathWithSutherlandHodgman(),
>> the comment says
>> "Clip a single path with a given rectangle using the Sutherland
>> -Hodgman
>> algorithm. This is much faster compared to the area.intersect method,
>> but
>> may create dangling edges." 
>> I think these danling edges are now removed in the
>> RemoveObsoletePointsFilter, so maybe it is worth 
>> trying. 
>> 
>> Gerd
>> 
>> 
>> 
>> 
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