To give you some background to this. The problem isn't in my application as such. I've published a UX called Component Column (demos
here) that allows components to be injected into grid cells. For that I need to manage their width to ensure they fit the column. A panel collapse in a cell can cause the vertical scrollbar on the grid to disappear, which kicks off a column resize. It's the column resize that kicks off my resize logic, I'm largely oblivious to the fact that there's a collapse animation going on.