Wrong pagination with "BeforeProcessRowList"

On my list page, I have the records per page set to 20.

I use the event "BeforeProcessRowList" (in the List page: Before record processed) to display only records from a department. (returning true/false)
Problem : Pagination appears to be using the original complete set and I obtain a lot of pages with per example 2 records on the first page and 3 on the second page...
This problem is exactly the same as this article:

Phprunner-link
Is there a solution to properly display records ?

Thanks in advance for your help

Pascal