[Qgis-user] getting QgsMapCanvasSnapper to work

[Marco Hugentobler]

Hi Martin

Thanks a lot!
It works for me now.

Regards,
Marco

On Wednesday 19 November 2008 21:12:39 Martin Dobias wrote:
> Hi,
>
> On Tue, Nov 18, 2008 at 11:00 PM, Hugentobler  Marco
>
> <marco.hugentobler at karto.baug.ethz.ch> wrote:
> > Hi Cedric
> >
> > I used your code lines and started the debugger. It seems that the
> > QgsMapCanvasSnapper works correctly. I think the problem has to do with
> > the QList reference in the binding:
> >
> > int snapToCurrentLayer( const QPoint& p, QList<QgsSnappingResult>&
> > results, QgsSnapper::SnappingType snap_to, double snappingTol = -1, const
> > QList<QgsPoint>& excludePoints = QList<QgsPoint>() );
> >
> > I tried to change that to:
> >
> > int snapToCurrentLayer( const QPoint& p, QList<QgsSnappingResult>&
> > results /Out/, QgsSnapper::SnappingType snap_to, double snappingTol = -1,
> > const QList<QgsPoint>& excludePoints = QList<QgsPoint>() );
>
> you're right, this is the correct binding. I've fixed that in r9671.
> Now in python one will call snapToCurrentLayer like this:
>
> (retval, results) = mcs.snapToCurrentLayer(pnt,
> QgsSnapper.SnapToVertex, 0.002, [] )
>
> The last two parameters are optional also in Python.
>
> > But then Python complains about a wrong type of the results parameter
> > with your code. I tried to use a 'QList' instead of '[]', but it seems
> > there is no QList in PyQt?
> >
> > Python experts: How can we deal with QList in PyQGIS?
>
> As Carson noted already, you can use python array for QList  (and
> python dictionary for QMap).
> Python doesn't support C++-style templates, so SIP allows developers
> to implement conversion between templates and python objects, this
> mechanism is used in PyQt for these conversions.
>
> Martin

-- 
Dr. Marco Hugentobler
Institute of Cartography
ETH Zurich
Technical Advisor QGIS Project Steering Committee