Using the y-coordinate of the polygon's bounding box, this
simple algorithm intersects the polygon with the horizontal
center line of its bounding box. The x-coordinate of the label
point is the center of the longest segment of this intersection
that is inside the polygon.
KML and WKT don't specify a winding order, so we write those out in CW/CCW order (for exterior/interior). GML references ISO 19107 that specifies CCW/CW, so we serialize in that winding order.
Having hand generated all this GML data the first time around, I reserve the right to modify it for the tests.
As suggested by @tschaub in #674, geom.pointInPoly is not needed
if we have geom.LinearRing#containsCoordinate. This pull request
also adds tests and documentation on the limitations of the
containsCoordinate method.
I think for now it is ok to keep geometry/topology functions as
simple as possible in ol3. If we decide to not rely on third
party libraries like jsts for topology operations, we can always
refine what we have and e.g. port topology operations over from
ol2.
Previously, a lookup object containing start indexes was also used. This allowed us to remove arrays of vertices and properly update the start indexes for remaining coordinate values. In order to provide callers with stable identifiers and to work with arrays of integers alone, we cannot support a remove method. I think this is worth revisiting. Even if the array length cannot be changed in WebGL, we don't need to also impose the restriction outside. Instead, the WebGL renderer could be notified when array sizes change and update itself accordingly. I think there is more value in providing geometries with stable identifiers.
This common structure is used to store vertices for all geometry types. A slight optimization could be made by creating yet another structure to store point vertices - since these don't need to have a counts array (always 1). Creating a new structure would mean saving memory at the expense of more lib code to transport. The coordinate value lookups are not negatively impacted by using the same structure for points and higher order geometries. Since the first change above goes against my instincts, I'm not making this second change (to add another structure for shared point vertices).
Its not clear that we will be able to leverage the Float64Array. It may also be that the overhead of constructing these small arrays negates any benefit of faster access. And for all coordinate arrays, we'll need arrays that grow/shrink.
