The ol3 version of the library is more advanced and complete. It can also
parse into flat array. It can handle unsigned integers, signed integers
and floats.
With two nested controls (DragFeature, SelectFeature), which - among
others - activated two OpenLayers.Handler.Feature instances, the
ModifyFeature control was fragile and hard to debug.
The issue that @iwillig, @bartvde and myself tried to track down was
that the two Feature handlers interfered with each other, making it hard
to select features on mobile devices, and causing points to jump during
dragging because of not updated last pixel positions.
With this refactoring, there are no more nested controls. All that's left
is a Drag handler. All tests pass. I had to remove one test that checked
for dragging of an unselected point while another was selected, because
now (and partially even before this change, thanks to the ugly drag
handler hack that is now removed) dragging a point will also select it,
saving the user an extra click.
Using the new defaults, we don't need to pass options to the Navigation
control anymore. As a side effect, we get ZoomBox, but need to add css for
it to work properly. For users outside Vienna, an OSM fallback layer was
added which gets activated when the viewport does not intersect Vienna.
Quick explanation:
Let targetCenterPx be described by PX and PY. Let oldRes and newRes be R0 and R1 respectively. Let centerPx (center after zoom) be described by CX and CY. And assume there is some anchored pixel point out there that represents the same map location before and after zoom. Let this be the origin OX and OY.
We want to recenter the map on the provided box. This means the map distance between the origin and box center at R0 is the same as the map distance between the origin and the map center at R1.
That is,
R0 * (OX - PX) = R1 * (OX - CX), and
R1 * (OY - PY) = R1 * (OY - CY)
Or, solving for OX and OY:
OX = (R0 * PX - R1 * CX) / (R0 - R1), and
OY = (R0 * PY - R1 * CY) / (R0 - R1)
There are still tests failing, but this change addresses some of the new failures after 4b163e0482 (which is an awesome improvement despite the test failures :).
