f2fce0f262
1) On Windows and Linux, the device enumeration now runs at a background thread, while it ran on the UI thread on idle, which may have been blocking on some rare Windows setups, see GH #3515 #3733 #3746 #3766 2) On OSX, the device enumeration now relies on OS callback, no polling is required. 3) Refactored for cleaner interface.