I originally put the rebase at the end of view_map, but at this point
the view is still at its native size and will ignore the motion event if
it falls outside of its native size. The only way to do this properly is
to rebase the cursor later - either after sending the configure, after
the view commits with the new size, or after applying the transaction. I
chose to do it after applying the transaction for simplicity.
I then attempted to just call cursor_rebase after applying every
transaction, but this causes crashes when exiting sway (and possibly
other places) because cursor_rebase assumes the tree is in a valid
state.
So my chosen solution introduces transaction_commit_dirty_with_callback
which allows handle_map to register a callback which will run when the
transaction is applied.