Open Radar

 
A very common use case I have is that I have e.g. a status text view, a progress bar view, and a pushbutton to Cancel.

Now in most cases, the progress bar is invisible, because the operation is quick, but in a few cases, I need the progress bar.

So I want the pushbutton to be at a certain distance below the status text when there's no progress bar, but want it to make room for the progress bar when that is visible. I would also like to be able to just do a binding to the "hidden" property on the progress bar to trigger this behaviour.

Therefore, it would be great if there was a layout constraint that can be set on a view that binds to its bottom when the view is visible, but to its top when it is hidden (thus moving the bound view over the hidden one when needed). This would probably also have to ignore the value of "constant" in that case.

Similarly, it would be good to have the same behaviour for left/right with leading/trailing alignments, and for left/right and right/left.