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

[Marco Hugentobler]

Hi Maciej

> > Issue 2:  a) Could be a bug, I have to check that.
> >
> > b) Possibly qgis makes a polygon during intersection removal where
> > postgis enforces a multipolygon.
>
> Should QGIS enforce *polygon* then, instead of obeying the layer's
> *multipolygon* geometry type? I think it shouldn't.

I also think so. 
Internally, qgis makes a polygon first, but it should make a multipolygon 
consisting of one polygon if the layer type is multipolygon.

> But no layer in the project has the individual snapping set - no layer
> is checked in the "Project Properties>Snapping options"! The default,
> QGIS-wide snapping setting should take effect for layers which don't
> have an individual snapping set - but it doesn't. This does look like a
> bug to me. If it isn't, what is the point of default project-independent
> snapping setting?

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. Otherwise, if a user changes any project property and clicks 
ok, the snapping will be off for all layers.

I don't think that unchecked layers should automatically have the default 
snapping tolerance. Because it is possible that a user don't want to snap to 
some layers at all.

Regards,
Marco



Am Freitag 29 Februar 2008 19:52:33 schrieb Maciej Sieczka:
> Hi Marco
>
> Marco Hugentobler pisze:
> >  The option "Enable topological editing" is for editing and maintaining
> > common boundaries in polygon mosaics. If you enable it and move boundary
> > vertices afterwards, it should be moved for all adjacent polygons.
> > Similar for insertion of new feature, delete vertex, add vertex and even
> > split feature.
> >
> > The option "Avoid intersection of new polygons" is to quickly digitise
> > adjacent polygons. If you already have one polygon, it is possible with
> > this option to digitise the second one such that both intersect and qgis
> > then cuts the second polygon to the common boundary. The advantage is
> > that users don't have to digitize all vertices of the common boundary.
> >
> > The 'search radius for vertex edits' is important if you move/add/delete
> > vertex. It is the distance from the click point where qgis looks for the
> > nearest matching vertex
>
> Cool. Thanks for clarifying these.
>
> > Issue 1: The default snapping tolerance applies to the current layer if
> > nothing has been saved into the project. As soon as you press 'apply' in
> > the project properties, qgis takes the (more detailed) project settings
> > which can be differentiated by layer. So this is a feature, not a bug :-)
>
> But no layer in the project has the individual snapping set - no layer
> is checked in the "Project Properties>Snapping options"! The default,
> QGIS-wide snapping setting should take effect for layers which don't
> have an individual snapping set - but it doesn't. This does look like a
> bug to me. If it isn't, what is the point of default project-independent
> snapping setting?
>
> > Issue 2:  a) Could be a bug, I have to check that.
> >
> > b) Possibly qgis makes a polygon during intersection removal where
> > postgis enforces a multipolygon.
>
> Should QGIS enforce *polygon* then, instead of obeying the layer's
> *multipolygon* geometry type? I think it shouldn't.
>
> Maciek



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