[mkgmap-dev] [PATCH v1] preserve edges introduced by clipping and splitting

Sun Jan 17 17:09:48 GMT 2010

Hi Mark,

I have not tested this patch. I expect it to work, but I think it is a 
suboptimal solution.

You set the preserve bit on all lines which are exactly horizontal or 
vertical.
Wouldn't it be cleaner way, to set the preserved bit at the place, where 
the new nodes are generated, i.e. in the clipping code?

This bit may be set in the multipolygon code too at the newly introduced 
cuts. (which are not vertical btw.)

This may be a little more work, but a clean design will always pay out.

Regards,
Johann

Mark Burton schrieb:
> This patch stops the DP filter from discarding points at either end of
> a horizontal or vertical line segment (such segments are created by the
> clipper and also by the polygon splitter and, of course, could occur
> naturally in the OSM data but I'd guess they are relatively rare).
>
> The benefit is that polygons lose those ugly artifacts (e.g. weird thin
> triangles) that sometimes occur at tile boundaries or where they have
> been split (when zooming out in mapsource).
>
> For me, mapsource still displays the odd spurious horizontal or
> vertical line but as it goes away when the screen is scrolled, I am
> assuming it is a mapsource bug rather than ours.
>
> Please try it out and report.
>
> Mark
>
>   
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