[Qgis-developer] About digitizing with GRASS Plugin

m roy royroge at outlook.com
Mon Oct 19 06:05:19 PDT 2015

Il 19/10/2015 12.41, Radim Blazek ha scritto:
> It is not possible to add in QGIS a layer without a type. So when a 
> new empty layer is created, a type must be chosen. The type selected 
> by user is only used for the layer added to canvas/legend, the created 
> vector map is empty. 

Ok, I see, could it be better to disable point and line tools
while working with polygons and so on? Just an idea.

>> This can be confusing, developing some kind of hybrid between the shapefile
>> and GRASS own vector format, will also "invalidate" all
>> existing GRASS documentation about vector editing and GRASS
>> vector format. We'll need to be overly zealos to explain when
>> and how things work differently in QGIS otherwise it will be quite
>> confusing for new users.
> I don't think that it invalidates all documents about digitizing, the
> principles and the format is the same. The editing tool is different
> and it has some particularities which I'll describe in QGIS
> documentation. It is not possible to support all the flexibility of
> GRASS vector format through QGIS interface.

Well yes, sorry, not all documentation of course.

>> (2) *Attribute table editing*:
>> not able to figure out how it works, i managed
>> to edit single feature using the "Identify Features"
> Changing the values in table cells (when editing) does not work?
Opening the attribute table i get a lot of records with NULL values
I can imagine that those are for boudaries and the filled ones are
centroid records (?)

> Regarding the symbology of boundaries, I am convinced that the 
> distinction between area/area
> and area/isle used in GRASS editor is useless while distinguishing of 
> boundaries with topological error is essential for effective editing. 
> Radim 

Well actually in GRASS you simply have different colors based
on the topology of boundaries, but I understand now,
given the QGIS layer limitations you explained at point (1),
that this may not be possible because QGIS layer does not
have any information about boundaries relative positions.

Thanks, Roy

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