I’m trying to find some hints where I should search for this topic but I’ve nothing found – and I spent many hours on this.
I’m also trying to get the current coordinates out of the current displayed viewport from the OpenLayers map to add only these vectors that are in the current bounding box of the current viewport.
For OpenLayers 2:
…will return a Bounds, which you can then use to get the lat/long coordinates in any number of ways: http://dev.openlayers.org/apidocs/files/OpenLayers/BaseTypes/Bounds-js.html#OpenLayers.Bounds
Ideally, you’d turn the vectors into Geometry objects and check them against Map.getExtent() using Bounds.intersectBounds() to see if they’re in the current viewport.
For OpenLayers 3:
…will return an array of coordinates, representing the bounding box of the extent.