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

[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