Did something break with the selection?

[Silvio Heinrich]

I don't know if someone worked on the selection code but it could be 
that something broke there.
Just try the following.
Create a new document and then use the gradient tool and paint a 
gradient over the document.
At this state it should work.
Then select an arbitrary region of the canvas and use the gradient tool 
again.
Now it does nothing and after you deselect everything the gradient tool 
still won't work.
After restarting the gradient tool should work again.
And I noticed that the preview capability of the filters don't work anymore.
But I think that has the same root because the filters behave
like the gradient tool they stop working after you select something.
But after thinking about this it could be that the blending mode branch 
broke something there
if the selection code relies on some specific CompositeOp.
I mean the one selection test that broke used the subtract CompositeOp 
for some reason.
If the selection code really needs the subtract CompositeOp it needs to 
set the channel flags right
to restore the old behavior.

I don't... does anyone know more about the selection code works?