This should help to improve the situation described in bug 451362. However this might help to coalesce reorder events only. It doesn't address remove or hide events. For example: 1. child remove, parent remove -> two remove events, one reorder for parent's parent 2. child hide, parent remove -> hide and remove events, one reorder for parent's parent 3. child remove, parent hide -> remove and hide events, one reorder for parent's parent Here this bug fixed reorder events issue for the case #1. The meantime we get two reorder events, one is for parent, another is parent's parent.

So for reorder events is the idea to only fire the reorder on the oldest ancestor?

(In reply to comment #2) > So for reorder events is the idea to only fire the reorder on the oldest > ancestor? For the topest, the same like for any other coalescent events if I follow your question right.

Comment on attachment 397254 [details] [diff] [review] patch r=me for the test part with a few nits: >+ function coalescenseBase(aChildAction, aParentAction, According to David, this is spelled "coalescence" (ce at the end). Please change. >+ // unexpected evetns t and n need to be swapped :) >+ function removeOrHideCoalescenseBase(aChidID, aParentID, You're using "aChidId" in a lot of places, but not everywhere. I suggest to correct to "aChildId" and be consistent. ;) >+ * Hide parnet node and then remove its child node. "parent". >+ * Remove parnet node and then hide its child node. The same. Can you kick off a try server build so I can play with it some?

Comment on attachment 397254 [details] [diff] [review] patch r=me. I had many questions but eventually answered them. I want a bigger brain.

The only possible perf hit I could see was that we have to set up a function call each time an event is added, whereas we removed the dupes etc in a for loop before.

(In reply to comment #4) > Can you kick off a try server build so I can play with it some? Sure - https://build.mozilla.org/tryserver-builds/surkov.alexander@gmail.com-try-ea1429164cc2/

Comment on attachment 397254 [details] [diff] [review] patch This works as expected, and manual tests didn't show any regressions. r=me, thanks!

landed on 1.9.3 - http://hg.mozilla.org/mozilla-central/rev/dfa26670be9f

This causes noticeable performance problems; see bug 522847.