The only feature on the temporary layer is now the
vertexFeature, and the temporary layer's style is dynamically
changed to the style of the layer whose segment is being edited
(the topmost layer if more than one segment are being edited).
With this simplification, we can also put all segments on a
single RTree. Finally, we no longer rely on structures set on
layers - all we need is now on the instance itself.
This refactoring also changes the way we define layers to
participate in modification - by using an array or a filter
function, or assuming all layers if no layers property is set.
The RTree cannot work with NaN coordinates. So instead of
preparing a vertexFeature before we know a coordinate, we now
lazily create the vertexFeature.
In combination with the additional squaredDistanceToSegment
check we can ensure that a future vertex is only created on one
segment per feature, and only on the segment that it appears on.
This change also renames the misleading dragVertices_ member to
dragSegments_.
This is a first draft. The way geometry changes are handled for
now is a bit clumsy. Both updating the feature cache RTree and
making the layer aware of feature and geometry changes could be
handled in a smarter way if these changes would be made through
the layer instead of directly on the geometry or feature.
The tests revealed that polygons can be drawn with counter-clockwise exterior ring order. In the polygon constructor, we enforce clockwise winding for exterior rings. So after drawing, we pass polygon coordinates back to the constructor before adding feature to the target layer.
This allows us to cast single-part geometries to multi-part types before adding features to the target layer. This doesn't yet allow for drawing multi-part geometries with multiple parts. That can be handled separately.
`click` events are fired only if the mouse action button is pressed. This prevents `click` events from being fired when the middle mouse button is used.
Also, without this commit, in Chrome with emulated touch events enabled, double-clicking the map doesn't zoom the map. This is because `ol.BrowserFeature.HAS_TOUCH` is `false` in that environment. The commit fixes it by testing `isMouseActionButton` on mouse devices only.
When we start dragging, we first handle dragstart and then set
the INTERACTING view hint and the dragging flag. To end dragging
in a symmetric manner, we have to first reset the INTERACTING
hint and dragging flag, and then handle dragend.
This flaw becomes obvious when using an interaction where no
animation is performed after the interaction. This can be seen
in the style-rules example when using the dragzoom interaction
(i.e. zoom using a drag box): the vector renderer will not
render the new resolution, because the INTERACTING view hint is
still set when the zoom box dragend is handled.
