Steps to Reproduce

run the attachment rod-performance.zul
scroll down to trigger rod

compare different ZK versions
http://zkfiddle.org/sample/3pd1e2a/1-rod-performance-8-6

Current Result

Degrading render times since 8.0.5
8.6.0.1 ~2.6s
8.5.2.1 ~2.1s
8.5.0. ~1.2s
8.0.5 ~1.1s

Expected Result

non degrading render time

Debug Info

Especially in this simple case columns/components in cells have FIXED widths.
Some how combobox/bandbox components have a bad effect on performance

try replacing a combobox in each cell ... (=> ~10s render time)
replacing the combobox in the first column, reduces the render time a lot.

In any case it is unexpected to see so many calls to fireSized -> and more surprising each of them seems to change some css resulting in forced reflows (all widths are fixed there's -> nothing to calculate)

Root Cause

Workaround