[Qgis-developer] Quick fixes and error communication for ftools

Tue Nov 24 02:06:42 PST 2015

Hi all,

Am 24.11.2015 um 11:01 schrieb Marco Hugentobler:
> Hi Alessandro, Matthias
>
>  >Is there no requirement for multi types?
>
> Afaik, the problem for f-tools are not the multi types, but only the
> geometry collections (containing geometries with different shape type).
> In my experience, if geos returns a geometry collection, it usually
> contains one 'expected' geometry and the others are slivers (@strk,
> please correct me if wrong).

There *could* be another problem, too [1]: 2.5D geometries, although I 
did not investigate this it should be checked because users cannot see 
the difference between them and regular 2D geometries.

Bernhard

[1] http://hub.qgis.org/issues/13167

>
>  >Based on what indicator should be chosen what to extract? Try polygons
> first, if there are none try lines, if there are none take points?
>
> One possibility would be to pass the expected shapetype (Point / Line /
> Polygon) to the function and take the best candidate (e.g. longest line,
> largest polygon area).
>
>  >How much effort (in time) do you think is required to implement this fix?
>
> Difficult to estimate. It seems straightforward to implement the
> extraction function. Then it needs to be called by the f-tools
> internally and be tested with a few examples. If unit tests are required
> (as mentioned by Alessandro), this seems to be the most time consuming
> task to me.
>
> Regards,
> Marco
>
> On 24.11.2015 10:42, Matthias Kuhn wrote:
>> Hi Marco
>>
>> Good to have your feedback, you probably know the problem best.
>>
>> On 11/24/2015 09:28 AM, Marco Hugentobler wrote:
>>> Hi
>>>
>>> >ad issue 1: update fTools to warn users when some features cause
>>> problems
>>> >ad issue 2: quick fix fTools to convert geometry collections to
>>> single geometry types
>>>
>>> A function that takes a geometry type and extracts the longest line /
>>> the largest polygon / the first point from the geometry collection
>>> should be straightforward to do.
>>
>> Is there no requirement for multi types?
>> Based on what indicator should be chosen what to extract? Try polygons
>> first, if there are none try lines, if there are none take points?
>>
>>>
>>> >These fixes/updates would be made available as fTools updates via
>>> the plugin installer asap
>>>
>>> If the fix does not take too long, we probably don't need a warning
>>> at all.
>>
>> How much effort (in time) do you think is required to implement this fix?
>>
>> Regards,
>> Matthias
>>
>>>
>>> Regards,
>>> Marco
>>>
>>> On 23.11.2015 21:35, Anita Graser wrote:
>>>> Hi,
>>>>
>>>> If you are following the psc list, you've probably seen the thread
>>>> discussing current shortcomings of ftools
>>>> (http://lists.osgeo.org/pipermail/qgis-psc/2015-November/003623.html)
>>>>
>>>> In short, the key issues are:
>>>> 1. When ftools encounter issues with certain features, warning
>>>> messages get written to the log but this is largely hidden from
>>>> users since they would actively have to actively monitor the log.
>>>> The problematic features are then missing from the results but this
>>>> is not always obvious.
>>>> 2. The above issue is more common now (since 2.10) since underlying
>>>> libraries more often (and correctly so) produce geometry collections
>>>> as outputs. These geometry collections are not handled well by the
>>>> current ftools code which is much older.
>>>>
>>>> To address these issues, the following suggestions have been made so
>>>> far:
>>>> ad issue 1: update fTools to warn users when some features cause
>>>> problems
>>>> ad issue 2: quick fix fTools to convert geometry collections to
>>>> single geometry types
>>>>
>>>> For the warnings, there's already a first PR draft
>>>> https://github.com/qgis/QGIS/pull/2432 which needs to be fleshed out.
>>>>
>>>> These fixes/updates would be made available as fTools updates via
>>>> the plugin installer asap.
>>>>
>>>> If you have ideas how to handle this efficiently or have already
>>>> implemented code that addresses similar issues, let us know.
>>>>
>>>> It would be good to have a quick discussion in order to be able to
>>>> provide improvements fast.
>>>>
>>>> Best wishes,
>>>> Anita
>>>>
>>>>
>>>> _______________________________________________
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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
>>>
>>>
>>> _______________________________________________
>>> Qgis-developer mailing list
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>>> List info:http://lists.osgeo.org/mailman/listinfo/qgis-developer
>>> Unsubscribe:http://lists.osgeo.org/mailman/listinfo/qgis-developer
>>
>> --
>> Matthias Kuhn
>> OPENGIS.ch -https://www.opengis.ch
>> Spatial • (Q)GIS • PostGIS • Open Source
>>
>>
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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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