Easier method to create parallel ways

[rvollmert@…]

I would like to be able to shift each node of a way a given distance into the direction that is vertical to the tangent to the way at that node. This should make it a lot easier to create parallel ways.

• I'm not sure what the UI should be like. It would be useful to shift a way by a specified distance (say 10m if you know that's how far the two ways of a motorway are separated), but also to have an interactive version, say a slider.

• To actually use this to create parallel ways, duplication should either be integrated, or (my preference) the present duplication should be modified to duplicate in place.

• For middle nodes, the normal direction could be computed as bisecting the angle of the two segments; the end nodes could be displaced at a right angle to the end segments.

• I have no idea how this would interact with projections. I think it would suffice to do these operations in screen coordinates. That might not work with specifying an exact distance to shift, though.

[anonymous]

Duplicate of #67.