[Qgis-developer] New GRASS plugin: a test drive

Radim Blazek radim.blazek at gmail.com
Fri Oct 9 01:23:40 PDT 2015

On Fri, Oct 9, 2015 at 1:34 AM, Pedro VenĂ¢ncio
<pedrongvenancio at gmail.com> wrote:
> I'm getting problems with symbology of polygon layers. Please see the
> screencast.
> https://dl.dropboxusercontent.com/u/5772257/qgis/grass_edit_polygons.ogv
> Note also that attribute form pop-up does not show up after each feature
> creation on polygons.
> After this, if I remove that polygon layer from QGIS canvas/toc, and add
> again from browser, then the symbology is ok (but the cat field is gone):
> https://dl.dropboxusercontent.com/u/5772257/qgis/grass_edit_polygons_2.ogv
> I'm using QGIS master compiled after this commit
> https://github.com/qgis/QGIS/commit/e703fc6044e3119c3b59fe9648f7dcf7edc2b714

Polygons in GRASS are formed by boundaries and identified by centroids
- point like features keeping the attributes. Normally, you digitize
boundaries and then place centroids inside. Boundaries usually do not
have attributes, centroids usually do have attributes. Without placing
a centroid into an area, the area exists (in layer 0), but does not
have attributes and will not appear in currently edited layer (layer 1
in this case).

The tool you used, 'Add Area' is just a shorthand to digitize closed
boundary (boundaries are line strings, not closed rings). Place a
centroid inside and you should see the polygon when editing is closed.
I would like to add also automatic placement of centroid when 'Add
Area' is used, but I don't know how yet, how to squash it to a single
undo operation with the boundary.


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