Correct placementFromDXFOCS()

Corrected placementFromDXFOCS() function with the indications provided by Autodesk (TM)
http://docs.autodesk.com/ACD/2011/ITA/filesDXF/WS1a9193826455f5ff18cb41610ec0a2e719-7941.htm
http://docs.autodesk.com/ACD/2011/ITA/filesDXF/WS1a9193826455f5ff18cb41610ec0a2e719-793d.htm#WSc30cd3d5faa8f6d81cb25f1ffb755717d-7ff5

src/Mod/Draft/importDXF.py

@@ -785,7 +785,7 @@ def placementFromDXFOCS(ent):
     Parameters
     ----------
     ent : A DXF entity
-        It could be of several types, like `lwpolyline`, `polynine`,
+        It could be of several types, like `lwpolyline`, `polyline`,
         and others, and with `ent.extrusion`, `ent.elevation`
         or `ent.loc` attributes.
 
@@ -802,6 +802,27 @@ def placementFromDXFOCS(ent):
     draftWPlane = FreeCAD.DraftWorkingPlane
     draftWPlane.alignToPointAndAxis(Vector(0.0, 0.0, 0.0),
                                     vec(ent.extrusion), 0.0)
+
+    # Riferimenti dell'algoritmo dell'asse arbitrario
+    # http://docs.autodesk.com/ACD/2011/ITA/filesDXF/WS1a9193826455f5ff18cb41610ec0a2e719-7941.htm
+    # http://docs.autodesk.com/ACD/2011/ITA/filesDXF/WS1a9193826455f5ff18cb41610ec0a2e719-793d.htm#WSc30cd3d5faa8f6d81cb25f1ffb755717d-7ff5
+    if (draftWPlane.axis == FreeCAD.Vector(1.0, 0.0, 0.0)):
+        draftWPlane.u = FreeCAD.Vector(0.0, 1.0, 0.0)
+        draftWPlane.v = FreeCAD.Vector(0.0, 0.0, 1.0)
+    elif (draftWPlane.axis == FreeCAD.Vector(-1.0, 0.0, 0.0)):
+        draftWPlane.u = FreeCAD.Vector(0.0, -1.0, 0.0)
+        draftWPlane.v = FreeCAD.Vector(0.0, 0.0, 1.0)
+    else:
+        if ((abs(ent.extrusion[0]) < (1.0 / 64.0)) and (abs(ent.extrusion[1]) < (1.0 / 64.0))):
+            draftWPlane.u = FreeCAD.Vector(0.0, 1.0, 0.0).cross(draftWPlane.axis)
+        else:
+            draftWPlane.u = FreeCAD.Vector(0.0, 0.0, 1.0).cross(draftWPlane.axis)
+        draftWPlane.u.normalize()
+        draftWPlane.v = draftWPlane.axis.cross(draftWPlane.u)
+        draftWPlane.v.normalize()
+        draftWPlane.position = Vector(0.0, 0.0, 0.0)
+        draftWPlane.weak = False
+
     pl = FreeCAD.Placement()
     pl = draftWPlane.getPlacement()
     if ((ent.type == "lwpolyline") or (ent.type == "polyline")):