Steps to Reproduce

use a classic theme e.g.breeze (themepack themes such as iceblue are additionally affected by ZK-4158)

run the attachment rod-performance-non-ee.zul
scroll down until new rows are rendered

compare the render times between 8.5.2.1 and 8.6.0.1

Current Result

the render/resizing times in 8.6.0.1 are worse than 8.5.2.1

8.5.2.1 (which is not great already) shows many forced reflows withing onResponseReady

8.6.0.1 (performs slightly worse during onResponseReady) and adds an additional heavy resizing block happening after onReponseReady

Expected Result

equivalent render times

Debug Info

replace the simple row, only rendering labels by the more complex row ... render times increase a lot

Root Cause

a single child with hflex="1" in the cells seems to cause significant slow down

Workaround

avoid hflex inside listcells, use EE rod if available