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QGIS 1.8.0 Mac OSX 10.6.8 These problems seem to be specific to Mac, as two Windows users don't have the problem.

Import a file as a vector:
TEST.CSV 

id;wkt  
1;"POLYGON((10 10,20 20,20 30,20 10))"  
...

The features import with correct values, individual points can be edited, and the layer saved as a shape file. But, no feature can be selected that was imported this way, so they can't be moved. New features added manually to the same layer can be selected and moved normally.

Probably related, only wkt-created features fully contained within the view are shown, wkt-features that have even a small bit outside the view vanish entirely. However, features added manually to the layer behave normally by showing the portion in the view. Layer editing capabilities are normal (full).

Has anyone suggestions as to a workaround for this? I'm hoping to migrate a dozen maps with 10,000 or so features from an old package that only exports true CSV:
x1,y1
x2,y2
...
I can script-edit this format to the above WKT, or similar text format. I don't have an app for .dbf so haven't been able to look there for any difference between WKT imports and QGIS-created features.

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  • I can only confirm that a CSV with above mentioned line works in QGIS on Win7. I've no access to Mac. – underdark♦ Apr 27 '13 at 16:59
  • Thanks underdark - that confirms what I understood from another user. Might you know of any QGIS tool that would show details of all the files QGIS uses for shapefiles? – johnsankey Apr 27 '13 at 19:53
  • Sorry, what do you mean? Vector file formats? Or the actual parts of a Shapefile: shp, prj, dbf, ...? – underdark♦ Apr 27 '13 at 20:06
  • the latter - I'm gessing dbf is the most likely to show a difference, shp second. – johnsankey Apr 27 '13 at 22:04
  • I've put the files on my website: johnsankey.ca/QGISWKT.ZIP in case anyone on Windows can read them. – johnsankey Apr 27 '13 at 22:47
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This is not a problem of MAC OS X or Windows, but a problem of your WKT geometry which is not valid. You can check it with the extension QuickWKT:

enter image description here

and the result is:

enter image description here

or independently of QGIS in Python with the module Shapely

from shapely.wkt import loads
wkt = loads('POLYGON((10 10,20 20,20 30,20 10))')
Traceback (most recent call last):
.....
"Could not create geometry because of errors while reading input."
 shapely.geos.ReadingError: Could not create geometry because of errors while reading input.

Why, because a polygon must be closed:

POLYGON((10 10,20 20,20 30,20 10,10 10)), for example

and the result is

enter image description here

and in Python with the module Shapely:

wkt = loads('POLYGON((10 10,20 20,20 30,20 10,10 10))')
list(wkt.exterior.coords)
[(10.0, 10.0), (20.0, 20.0), (20.0, 30.0), (20.0, 10.0), (10.0, 10.0)]

The expression is valid for a LINESTRING(10 10,20 20,20 30,20 10)

enter image description here

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  • Hi gene, I tried duplicating the start point at the end - no change. – johnsankey Apr 27 '13 at 16:30
  • Also, how do I install QuickWKT to my QGIS on a Mac? The download is a directory full of things and no directions on the README as to how to install it, also no mention of Mac/Linux/Windows, which has me worried. – johnsankey Apr 27 '13 at 16:40
  • I should add that QGIS seems to understand both cases: it created the same polygon in both cases, and didn't make a duplicate node in the 2nd case. – johnsankey Apr 27 '13 at 16:51
  • QuickWKT is a plugin and to install a plugin, you must use the Plugin/install plugin menu. As it is in Python, it n 'is no matter if it's Windows, Mac or Linux – gene Apr 27 '13 at 19:09
  • Got it - I didn't realize that QGIS won't look locally for plugins, only on-line. QuickWKT approves the WKT with the closing point added, but QGIS still has the problems I describe. – johnsankey Apr 27 '13 at 19:50
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For everybody, the Plain Geometry Editor plug-in in action, clicking on a point of one of the geometries in Edit mode:

enter image description here

and you can change the WKT chain

enter image description here

But if I try with your original geometry

enter image description here

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