At present in the UI controls, the selection and focus models expose multiple properties that should be considered to be atomic in nature (that is, they should always update at the same time, and it should not be possible that they reflect differing values). For example, selectedItem / selectedIndex / selectedCell, as well as focusedItem / focusedIndex. A similar argument could be made for the selectedIndices / selectedItems list, but these will be handled at a separate date.

The goal is to simply have it such that notifications for changes to these properties are not fired until they all represent the new state. This will remove a class of bugs and allow for future clean ups in the selection model and focus model code.