Blender Git Loki

Cocoa : use Cocoa NSWindow tag for identifying the window where a mouse/tablet/key event happened => enables some actions in inactive windows as per OSX standard

Previous code was assuming an event can only be sent from the active window.
On OSX, Right, Middle mouse buttons, mouse wheel and trackpad events are sent to inactive windows too.

For example, this allows to zoom, pan the view without changing the window order.