[Qgis-developer] Re: [Qgis-user] vector editing in QGIS - questions and issues (PostGIS biased)

[Marco Hugentobler]

Hi,

I changed the behaviour now such that the snapping settings is only changed if 
the user really opened the project snapping dialog and clicked 'ok'.

I'm quite open to suggestions about what reasonable defaults should be (this 
was the main point of our discussion below). Possibilities are:

- snap to editing layer with default tolerance but not to background layers. 
This is the current default and the suggestion of Micha. 
And it's the same as the behaviour prior to the merge of the advanced editing 
branch (it was not possible then to snap to background layers)

- snap to all vector layers using default snapping tolerance. This was what 
Maciej suggested below.


>I'd be also in favor
>of enabling the QGIS "topological editing" feature by default.

+1

cheers,
Marco



Am Dienstag 04 März 2008 12:08:26 schrieb Micha Silver:
> Maciej Sieczka wrote:
> > Marco Hugentobler pisze:
> > > Maciek wrote:
> > >> Marco wrote:
> >
> > Before you read on: NOTICE - I'm assuming that snapping = 0 is no
> > different than snapping "disabled". Is this correct? If it is, maybe
> > it would be better to remove the snapping checkbox for layers and use
> > spinbox with numbers only to simplify the dialog?
> >
> >> Ok, I see what you mean. In the snapping dialog of the project should
> >> be inserted the default snapping settings (which is snapping to the
> >> active layer with the default snapping tolerance) in case the
> >> snapping dialog was not changed already.
> >
> > Yes.
> >
> >> Otherwise, if a user changes any project property and clicks ok, the
> >> snapping will be off for all layers.
> >
> > I think differently. As long as default QGIS-wide snapping is !=0, all
> > layers which don't have inddividual setting set by the user, should
> > have snapping set on equal to default setting - unless the user
> > manually disables snapping for the given layer.
> >
> >> I don't think that unchecked layers should automatically have the
> >> default snapping tolerance.
> >
> > Then what is the point of default snapping setting at all? Look - as
> > long as you don't enter project properties and click OK, the default
> > QGIS snapping is on for all layers in the project. Once you go to
> > project props. and click OK, all snapping is suddenly disabled,
> > although you did not modify any setting related to snapping. Imagine a
> > user trying to guess what happened.
>
> In the kind of jobs I do, and what I can imagine others do, I would NOT
> want snapping automatically to all layers, but only the one layer I have
> set to snap. Maybe, as you suggest, there should not be any default
> project snapping setting at all, now that we have snapping for
> individual layers.
>
> > Note also that this was different in QGIS before introducing
> > individual snapping setting per layer. You only had the QGIS-wide
> > snapping setting, which was always active, for all layers. Now as soon
> > as you go to project settings for whatever reason and press OK that
> > snapping is disabled. This should be avoided.
> >
> >> Because it is possible that a user don't want to snap to some layers
> >> at all.
> >
> > The user can disable snapping for a certain layer, if he needs to.
> >
> > Another thing - IMO users more often need snapping than they don't.
> > Help users not to digitize overlapping features by default, eg.
> > promote using snapping rather than not using it. I'd be also in favor
> > of enabling the QGIS "topological editing" feature by default.
> >
> > What I hate most in GIS are all those overlapping polygons and lines
> > which I have to tediously correct topology for, re-calculate their
> > area and length, explain the vendor what is wrong about his data.
> > Please promote topological practices.
> >
> > Maciek
> > _______________________________________________
> > Qgis-user mailing list
> > Qgis-user at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/qgis-user
> >
> >
> >
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-- 
Dr. Marco Hugentobler
Institute of Cartography
ETH Zurich
Technical Advisor QGIS Project Steering Committee