georchestra/georchestra — pull request #263 by fgravin (2013-09-03 14:50:46+00:00)
Title: Mousescroll on map bug fix

If you mouse scroll on a map without any visible layer, then the map doesn't zoom in/out.

This is a bug in OL.
We hack this by using a OpenLayers.Layer.Grid instead of a OpenLayers.Layer for the fake background layer. This way, there is always a visible blank layer, so the mouse scroll works.