Fixed Distance Buffer makes 0 (zero) distance invalid

[qgib]

Author Name: Steve Lowman (Steve Lowman)
Original Redmine Issue: 18541
Affected QGIS version: 2.18.17
Redmine category:processing/qgis
Assignee: Victor Olaya

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I do a fixed-distance buffer on a polygon layer with the distance parameter as 0.0 (zero). This fails because 0 (zero) is classed as an invalid distance.

In older QGIS versions, and in the OGR 'Buffer Vectors' algorithm, this works well, and I have often used it as a method to remove most types of invalid geometry. Therefore, I think this is a regression.

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• zero_distance_fixed_buffer_log.txt (Steve Lowman)

[qgib]

Author Name: Nyall Dawson (@nyalldawson)

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This is not a qgis bug, it's a bug in SAGA.

You could try the other buffer algorithms such as the native QGIS "fixed distance buffer" algorithm instead.

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• resolution was changed from to up/downstream
• status_id was changed from Open to Closed

[qgib]

Author Name: Steve Lowman (Steve Lowman)

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Thank you, yes, I was testing the tool in the wrong list. I was trying to test whether the native tool can work on features with invalid geometry. It cannot (see #25189), so I think it is best to use the OGR buffer tool for fixed distance, and perhaps the Saga one for variable distance buffers.

I wonder whether I should make a feature request to replace the native buffer tools in the Vector menu for QGIS 2, due to the outcome of #25189?