Sway maintains a list of pending transactions, and tries to merge
consecutive transactions applying to the same views into one. Given
a pending transactions list on views {A, B, C} of:
A -> A' -> A'' -> B -> B' -> B''
Sway will collapse the transactions into just A'' -> B''. This works
fine when doing things like resizing views by their border. However,
when interactively resizing layouts like H[V[A B] C], we end up with
pending transaction lists like:
A -> B -> C -> A' -> B' -> C' -> A'' -> B'' -> C''
Previously, Sway would not be able to simplify this transaction list,
and execute many more transactions than would be necessary (the final
state is determined by {A'', B'', C''}).
After this commit, the transaction list gets simplified to A'' -> B'' ->
C'', resolving performance problems (that were particularly noticeable
with high-refresh-rate mice).
Fixes#5736.
cc8d318aa1