Marker line - Negative Line offset moves symbol to the other endpoint

[qgib]

Author Name: Sandro Santilli (@strk)
Original Redmine Issue: 13811
Affected QGIS version: 2.8.3
Redmine category:symbology
Assignee: Sandro Santilli

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To reproduce:

1. New project
2. Add a simple (2 vertices) LINESTRING -- for example with QuickWKT plugin
3. Go to layer properties, Style TAB
   3.1. add Marker line, set "on last vertex only" and "Rotate marker" (should be already set)
   3.2. pick an arrow as "Simple marker"
   3.3. Change "Line offset" field in Marker placement to a negative number and see how it moves the arrow to the first vertex (from last)

This is likely a misues of GEOS OffsetCurve which is known to return a reversed line on negative offsets

[qgib]

Author Name: Sandro Santilli (@strk)

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Confirmed, I've a working patch. While testing it I also found that an offset of -0.0 (negative zero) makes the symbol disappear

[qgib]

Author Name: Sandro Santilli (@strk)

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Patch staged here: #2442
If anyone has pointers to add a testcase I think it would be worth it (symbols often break).
Also, I couldn't check if the bug is still present in master.

[qgib]

Author Name: Sandro Santilli (@strk)

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confirmed also master is affected. I'm working on an automated testcase.

[qgib]

Author Name: Sandro Santilli (@strk)

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Fixed in changeset "824fd7bf32a45e278f2ec2fe9fa1c7228c9fb27f".

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• status_id was changed from Open to Closed