steps to reproduce

1. run the attached zul
2. click "open All Without Notify" button
3. click "open All With Notify"
4. comparing the performance

actual result

• client-side rendering takes a long time. in openWithoutNotification.cpuprofile, open() gets longer and longer.
• Using "notify change" takes less time than "open All Without Notify" case.

debug info

• please try to optimize it to avoid taking longer and longer time when the number of open node increases.
• At client side, opening nodes one by one requires much time to calculate width. is it possible to reduce width calculating time?
• please check attached screenshots