Map loses focus after clicking on map controls

[jacobtoye]

After clicking the zoom button you can no longer use the keyboard to navigate the map. This is because the button now has the focus and the keyboard events don't fall through.

My initial thoughts are to re-focus back on the map container in the zoom button handlers. Could you see this having any adverse effects?

refs Leaflet/Leaflet.draw#209

[mourner]

Yeah, seems fine as keyboard users would still use +/- to zoom.