Comment 2 for bug 170858

See the attachment, plane.svg. Inspect how the orange color
was put to the image. I am talking about a fast method to
put color below left wing of the plane. The shape of the
wing is pretty basic, so I put color manually. But more
complicated shapes would need more work.

I think, I could write an extension, see 'the extension' in
plane.svg. The numbers are nodes indices in the svg file.

1. User passes nodes that mark 'the break' in the shape. In
plane.svg those are nodes 3 and 9.

2. The extension collects the nodes from 3 to 9 and end with
lineto(9,3)

3. The resulted shape is the color-shape

The algorithm needs some more details, I know.

I couldn't figure it out how to find the color-wing-shape
without user pointing which nodes start 'the break'. Finding
the points at which line changes from inner to outer seems
impossible - take the 'S' letter for instance or similar shapes.