Positional and cross-filter corruption

[GrandyB]

Using hotkeys to go in/out in quick succession can completely break the position data of the sources in the scene, and it a royal pain in the ass to fix. It needs some safeguards against this happening.

[CatxFish]

There are some difficult to discover the other filter current status , I am not doing modification this time until I figure out an appropriate solution.

[GrandyB]

Been attempting to get the size issue again but to no avail, however I am noticing strange behaviour when using multiple filters on the same source. Not providing a start point isn't resulting in the behaviour I'd expect.

I'm inclined to implement #10 and fix it as part of that, as hopefully the clarity of separating behaviours out in that way will make it easier.