[Qgis-developer] Virtual columns in QGIS, was: Re: [Qgis-user] object labels

[kimaidou]

Hi,

+1 for Mayeul Nathan. This "virtual column" would be a very handy tool ! E.G
for labelling

kimaidou

2011/7/28 Andreas Neumann <a.neumann at carto.net>

> Hi Nathan,
>
> Good to hear that you are working on this.
>
> I just wonder if it wouldn't make sense to have a general purpose "virtual
> column" that could be introduced in QGIS. This would be useful for:
>
> * labeling
> * map tips/QGIS server tooltip display
> * symbology
> * plugins
> * others?
>
> It would be convenient to use the field calculator, but instead of just
> writing out to a physically existing column it would create a new virtual
> column, just like a virtual column in a database view.
>
> Otherwise one would have to develop the same functionality several times -
> for labeling, for tooltips, etc.
>
> Do you think it would be feasible to implement this on a lower level in
> QGIS so that users could transparently work with virtual columns wherever
> they want?
>
> Andreas
>
> On Thu, 28 Jul 2011 16:09:56 +1000, Nathan Woodrow wrote:
>
>> My upcoming patch that adds expression based labels will be able
>> to achieve this once it's completed;  I'm just cleaning up the UI
>> and testing everything then I will get the guys to merge it in.
>>  Until then you will need to create a new column.
>>
>> - Nathan
>>
>> On Wed, Jul 27, 2011 at 9:15 PM, Torsten Lange  wrote:
>>
>>  Ok, thank you, Andreas!
>>>
>>> Torsten
>>>
>>> Am Mittwoch 27 Juli 2011, 11:00:01 schrieb Andreas Neumann:
>>>
>>>   Hi,
>>>>
>>> >
>>> >  Currently, you have to create a new column. I usually create a
>>> view in
>>> >  Postgis for this purpose.
>>> >
>>> >  It is in on the wishlist that one can create a "virtual" column
>>> - not
>>> >  only for labeling, but also for map tips and perhaps
>>> symbolization.
>>> >  Until then you have to do it yourself.
>>> >
>>> >  Andreas
>>> >
>>> >  On Tue, 26 Jul 2011 22:51:34 +0200, Torsten Lange wrote:
>>> > > Hi,
>>> > >
>>> > > Is there a way just to print - lets say - the first four
>>> letters of a
>>> > > objects
>>> > > name? Or must I create a new row for that?
>>> > >
>>> > > Thank you, Torsten
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>>>
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>>
>>
>>
>> Links:
>> ------
>> [1] mailto:Qgis-user at lists.osgeo.**org <Qgis-user at lists.osgeo.org>
>> [2] http://lists.osgeo.org/**mailman/listinfo/qgis-user<http://lists.osgeo.org/mailman/listinfo/qgis-user>
>> [3] mailto:Qgis-user at lists.osgeo.**org <Qgis-user at lists.osgeo.org>
>> [4] http://lists.osgeo.org/**mailman/listinfo/qgis-user<http://lists.osgeo.org/mailman/listinfo/qgis-user>
>> [5] mailto:tlange at gwdg.de
>>
>
> --
> --
> Andreas Neumann
> Böschacherstrasse 10A
> 8624 Grüt (Gossau ZH)
> Switzerland
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