Steps to Reproduce

run the attached example measure-onresponse.zul
scroll down to trigger new rows to be rendered

observe the browsers console

Current Result

chrome breeze:

(index):881 zAu._onResponseReady: 0.283935546875ms
(index):881 zAu._onResponseReady: 0.036865234375ms
(index):881 zAu._onResponseReady: 0.02392578125ms
(index):881 zAu._onResponseReady: 77.556884765625ms (that's the render time)

chrome iceblue_c:

(index):881 zAu._onResponseReady: 0.261962890625ms
(index):881 zAu._onResponseReady: 0.02099609375ms
(index):881 zAu._onResponseReady: 0.017822265625ms
(index):881 zAu._onResponseReady: 574.68896484375ms

when using "iceblue_c" chrome takes ~700% time to render the new rows

Expected Result

equal or marginally different render time

Debug Info

looking into the performance profiler, shows most of the time is spent during "Recalculate Styles" indicating a CSS problem

Root Cause

certain combinations wildcard CSS selectors negatively affect the CSS performance

e.g.:
just adding those 2 empty style rules to the breeze theme, causes a similar performance drain:

.z-combobox-input[readonly]+* { }
.z-combobox-disabled>*:hover+* { }

replacing the wildcards with specifc selectors helps (not sure if a is the correct element, the implementor needs to check carefully)

.z-combobox-input[readonly]+a { }
.z-combobox-disabled>*:hover+a { }

the attachment contains the iceblue_c zk.wcs with the problematic 9 rules commented out

commenting in a single of them doesn't make it slow, only certain combinations of at least 2 of these rules cause the slowdown

Workaround