This commit does two things: adds a weak reference to the parent
container of each SplitNode.Container and SplitNode.Leaf and moves the
"direction" of a split out of the SplitNode enum and into the
SplitNode.Container struct as a field.
Both changes are required for supporting split resizing. A reference to
the parent in each leaf and split container is needed in order to
traverse upwards through the split tree. If the focused split is not
part of a container that is split along the direction that was requested
to be resized, then we instead try and resize the parent. If the parent
is split along the requested direction, then it is resized
appropriately; otherwise, repeat until the root of the tree is reached.
The direction is needed inside the SplitNode.Container object itself so
that the container knows whether or not it is able to resize itself in
the direction requested by the user. Once the split direction was moved
inside of SplitNode.Container, it became redundant to also have it as
part of the SplitNode enum, so this simplifies things.
The resizeIncrements property is only modified when the cell size of the
focused window changes. If two splits have the same cell size then the
property is not modified when focusing between the two splits.
Fixes#519
The core issue here was that `mouseEntered` was called AFTER
`cursorUpdate` (by Cocoa) so we were messing up our NSCursor state. To
fix this more robustly, all cursor state should ONLY be handled by
cursorUpdate and mouseEntered/Exit goes through that system now.
Without this, non-first-responder views would not receive mouse
entered/exit events. This would break some of our mouse hiding state.
See comments for more info.
This reverts commit c139279d479682c17f63d9b57c2d56608d09d16a, reversing
changes made to 4ed21047a734d7c586debe0026e3b6ea90ed1622.
We do want to do this but this broke bindings.
