[Qgis-developer] closestSegmentWithContext

Caio Hamamura caiohamamura at gmail.com
Fri May 6 05:15:44 PDT 2016


I've already used this function and it returned exactly the same you claim
to receive. But you can calculate the position yourself, it is actually
simple. Check it out:

http://stackoverflow.com/a/1560510/2548351



2016-05-05 13:25 GMT-03:00 Worth Lutz <wal3 at mindspring.com>:

> I'm trying to use "closestSegmentWithContext" method of QgsGeometry in a
> plugin. I don't seem to be getting what I'm expecting.
>
> Comparing
> http://qgis.org/api/classQgsGeometry.html#ac09505a6a8a29f244a37c6f336cd98e7
>
> with the following from:
> https://github.com/qgis/QGIS/blob/master/python/core/geometry/qgsgeometry.sip
>
>     /**
>      * Searches for the closest segment of geometry to the given point
>      * @param point Specifies the point for search
>      * @param minDistPoint Receives the nearest point on the segment
>      * @param afterVertex Receives index of the vertex after the closest
> segment. The vertex
>      * before the closest segment is always afterVertex - 1
>      * @param leftOf Out: Returns if the point lies on the left of right
> side of the segment ( < 0 means left, > 0 means right )
>      * @param epsilon epsilon for segment snapping (added in 1.8)
>      * @return The squared cartesian distance is also returned in sqrDist,
> negative number on error
>      */
>     double closestSegmentWithContext( const QgsPoint& point, QgsPoint&
> minDistPoint /Out/, int& afterVertex /Out/ ) const;
>
>
> When I try:
>
> results =
> self.selectedStreetSegment.geometry().closestSegmentWithContext(point)
>
>
> I get a results as:
>
> (2560.365846544, (2106395, 746610), 1)
>
> I take this to be (sqrDist, minDistPoint, afterVertex ).  It does not seem
> to be returning "leftOf" which is the value I'm looking for.
>
> Is something missing in that "sip" definition?  I do not know what I'm
> looking at so I may be looking at the wrong thing. In any case, I cannot
> seem to find the results I need.
>
> Thanks,
> --
> *Worth Lutz*
>
>
>
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