[Qgis-developer] Python API different from documented API?

Worth Lutz wal3 at mindspring.com
Fri May 6 07:25:06 PDT 2016


I'm finding that I'm spending lots of time trying to figure out method 
parameters in Python.

The documented QGIS API apparently does not match the Python API. See 
question in email below.  Compare the documents with the statement I 
ended up with and you see the differences.

It seems that I'm having to experiment to figure out what to do for many 
objects.

This is frustrating and I wonder if I am just missing something.


*Worth Lutz*


On 5/5/2016 12:25 PM, Worth Lutz wrote:
> 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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