Coordinate systems

[Håvard Fossli]

Consider this hierarchy 

 

If I want A.A.A.left to equal B.A.left I'm thinking I would have to write 

  A.A.A.left == (B.left) - (A.left + A.A.left) + B.A

In a general form it could be described as

  view1.left == (add intermediates coordinates from view1 up to common ancestor) - (add intermediate views from view2 up to common ancestor) + view2.left

Now this could probably be made into an expression

  expression = expressionForDiffBetweenViews(view1, view2);
  view1.left == expression + view2.left

Am I right? Or is there som better/other way? 

My biggest concern is how this should be implemented in the simplest fashion. It would be awesome to be able to say...

 
view1.centerY == view2.centerY

...regardless of order and structure. 

Much like described here

Ref: http://gridstylesheets.org/

How should I let cassowary be aware of coordinate systems?

All feedback is valuable. And I am especially interested in hearing from Ken, Alex and Dan.

Thanks,

Håvard