Comment 30 for bug 168695

OK I've moved the blocking code from tool-base to sp-canvas. This allows the node tool to correctly work. I should note here that the only tool to NOT call tool-base root_handler for events is the node-tool when releasing a mouse button when the mouse is outside of an object. This is because there's no item to run an event on. But this might make weird things happen IMO.

But that doesn't effect us here any more. Please test, I think this commit is a keeper.