artemp/mapnik — Issue #876: polyline clipping
Author: artemp
Created: 2011-10-11 16:40:05+00:00
State: open
Labels: Core_Library

We do not allow an option to enable clipping of polylines. Situations can occur then where data, like osm, has a very long diagonal line, whose bbox intersects with 100/1000's of tiles. But, while the line actually will not appear visually in 99% of those tiles, it will be fully processed and rendered outside of the visible canvas.

Here is a classic case: http://www.openstreetmap.org/browse/way/28095223

You would think that the usage of agg clipping with `ras_ptr->clip_box(0,0,width_,height_);` would provide this clipping, but that is not the case.