[Qgis-developer] Questions regarding new geometry engine
Marco Hugentobler
marco.hugentobler at sourcepole.ch
Fri Jun 5 02:20:09 PDT 2015
On 05.06.2015 09:17, Denis Rouzaud wrote:
> Hi Marco,
>
> Can you tell me if these two issues are related to your work?
> http://hub.qgis.org/issues/12885
> http://hub.qgis.org/issues/12886
I think so, therefore assigned the tickets to me.
Regards,
Marco
>
> Thanks a lot,
> Denis
>
> 2015-06-04 15:52 GMT+02:00 Marco Hugentobler
> <marco.hugentobler at sourcepole.ch
> <mailto:marco.hugentobler at sourcepole.ch>>:
>
> Hi Nyall
>
> >Firstly, I *think* that there's an issue with the
> >inheritance of some of the classes. Specifically QgsMultiLineStringV2
> >and QgsMultiPolygonV2. Currently both of these derive from
> >QgsGeometryCollectionV2, but I think they should derive from
> >QgsMultiCurveV2 and QgsMultiSurfaceV2. This would seem logical to me
> >since QgsLineStringV2 derives from QgsCurveV2 and QgsPolygonV2
> derives
> >from QgsCurvePolygonV2. It also would match with how I understand the
> >OGC simple features access specification describes (see 6.1.8.1 -
> >MultiCurve should be non-instantiable, 6.1.9 multiline is a
> >multicurve, and 6.1.13.1 and 6.1.14 for the corresponding
> >multisurface/multipolygon types). What's your thoughts?
>
> Yes, in the ISO and OGC models, MultiPolygon inherits from
> MultiSurface and MultiLineString from MultiCurve. The
> implementation of the geometryV2 classes differs a bit compared to
> the model, because most methods are implemented on
> GeometryCollection level (e.g. in the ISO model, length() and
> area() are not in the collection class). So there is little
> practical relevance if QgsMultiPolygon is derived from
> MultiSurface (and overwrites all its methods) or from
> GeometryCollection. One exception is the segmentize() method. By
> default (straight geometries), this is equal to a normal clone().
> As MultiSurface needs to overwrite it (may contain curved
> geometries), MultiPolygon would need to overwrite it again with
> the default behaviour if it was derived from MultiSurface.
>
> >MultiCurve should be non-instantiable
>
> In the OGC model, it is non-instantiable. In the ISO model (which
> is relevant here), it is left to the implementation if it is
> instantiable or not.
>
> Regards,
> Marco
>
>
> On 03.06.2015 09:05, Marco Hugentobler wrote:
>
> Hi Nyall
>
> Thanks for your input. I'll back in the office tomorrow and
> can give you more detailed answers to the technical questions.
>
> To the technical issues:
> Yes, I plan to fix them in the next time, but definitely
> before release ( fixed #12857 and started to look at #12836
> already). I think you should focus on other bugs, otherwise we
> risk to do the same work twice.
>
> Regards,
> Marco
>
>
> Am 02.06.2015 um 23:34 schrieb Nyall Dawson:
>
> Hi Marco (also cc-ing dev list)
>
> I've been looking over the new geometry engine and it's
> really nice
> stuff. It's fantastic to have this in QGIS and it's a huge
> improvement
> over the old geometry class. Thank you!
>
> I have a couple of questions regarding this which I'm
> hoping you can
> clarify for me. Firstly, I *think* that there's an issue
> with the
> inheritance of some of the classes. Specifically
> QgsMultiLineStringV2
> and QgsMultiPolygonV2. Currently both of these derive from
> QgsGeometryCollectionV2, but I think they should derive from
> QgsMultiCurveV2 and QgsMultiSurfaceV2. This would seem
> logical to me
> since QgsLineStringV2 derives from QgsCurveV2 and
> QgsPolygonV2 derives
> from QgsCurvePolygonV2. It also would match with how I
> understand the
> OGC simple features access specification describes (see
> 6.1.8.1 -
> MultiCurve should be non-instantiable, 6.1.9 multiline is a
> multicurve, and 6.1.13.1 and 6.1.14 for the corresponding
> multisurface/multipolygon types). What's your thoughts?
>
> Secondly, are you able to share your plans for bug fixing
> leading up
> to 2.10? There's a number of serious regressions following
> this work,
> and I'm wondering if I should be focusing on these during the
> sponsored bug fixing or whether you plan to tackle them before
> release? The biggest issues I see are:
> - #12836 : layers fail to render
> - unfiled: I get a lot of unknown exceptions when working with
> geometries. I can reproduce this consistently by trying to
> use the
> reshape tool on a polygon, or by rotating a map within the
> canvas or a
> composer.
> - #12843: simplify tool broken
> - i noticed there's also a number of stubbed methods in
> geometry with
> todo comments (eg QgsGeometry::buffer ).
>
> If you can share your plans then I can plan my work
> accordingly.
>
> Again, thanks again for this fantastic work!
>
> Nyall
>
>
>
>
>
> --
> Dr. Marco Hugentobler
> Sourcepole - Linux & Open Source Solutions
> Weberstrasse 5, CH-8004 Zürich, Switzerland
> marco.hugentobler at sourcepole.ch
> <mailto:marco.hugentobler at sourcepole.ch> http://www.sourcepole.ch
> Technical Advisor QGIS Project Steering Committee
>
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--
Dr. Marco Hugentobler
Sourcepole - Linux & Open Source Solutions
Weberstrasse 5, CH-8004 Zürich, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee
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