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

[Maciej Sieczka]

Hi

QUESTIONS:

What do the "Enable topological editing" and "Avoid intersections of new 
polygons" in Project Properties exactly do? What is the "Search radius 
for vertex edits" in Options>Digitizing? I can't find them covered in 
QGIS manual, website and WIKI. I'd be grateful for explaining them to me 
as I have to explain them to few other folks on Saturday :).


ISSUES:

1. Once I enter the "Project properties" and press "Apply" (without or 
with modifying any setting, with or without any layer added to project - 
doesn't matter), the "Default Snapping Tolerance", which I set in 
Option>Digitizing to "5", is not respected anymore when editing PostGIS 
layers from then on (like if set to 0). To enable sanpping I have to set 
it separately for each layer in Project Properties, which is tedious and 
was hard to guess what's going on. Looks like a bug, does it?

2. After "Avoid intersections of new polygons" is enabled, and the 
individual snapping for the layer is set in the Project Properties, 
following errors crop out:

a) During digitising PostGIS multipolygons an error "Could not remove 
polygon intersection" pops up from time to time. I can't see what is the 
pattern for that. A bug?

b) At saving changes to a PostGIS multipolygon layer, if a polygon 
touching another one is digitised, an "INSERT error" pops up: "ERROR: 
new row for relation "test_polygons" violates check constraint 
"enforce_geotype_the_geom"", and I cannot save changes. Seems a bug for 
sure.

Here's the metadata of an example "test_polygons" layer. Issues are 
reproducible with any multipolygon though AFAICT:

Storage type of this layer : Generic vector file
Source for this layer : dbname=topsecret host=topsecret port=topsecret 
user=topsecret table="topsecret"."test_polygons" (the_geom) sql=
Geometry type of the features in this layer : Polygon
The number of features in this layer : 3
Editing capabilities of this layer : Add Features, Delete Features, 
Change Attribute Values, Add Attributes, Delete Attributes, Change 
Geometries, Select Geometries by ID (unknown access method)
Extents:
In layer spatial reference system units : xMin,yMin 594842,5.68402e+06 : 
xMax,yMax 598419,5.68746e+06
Layer Spatial Reference System:
+proj=utm +zone=33 +ellps=WGS84 +datum=WGS84 +units=m +no_defs

Takes place on QGIS r8182 built and running against QT 4.3.2, GEOS 3.0, 
PgSQL 8.2.6, PostGIS 1.3.2, on amd64 Ubuntu Gutsy. Same happened in 
r8171. Please fix if possible.

Maciek