Following this method, I wanted to "place" some of my windows on specific viewports. For instance, I want Xchat to always start on my top right viewport (x=2, y=1). But after I have set everything up and clicked the "Close" button to validate it (I don't have any other action button, like "OK" or "Apply"), the only thing that get saved up are the viewport X and Y coordinates. The window class (in my case class=Xchat) remains empty.

This bug only occurs in the "Windows with fixed viewport" section; it works well in the "Windows with fixed placement mode", for instance.

How can I solve or circumvent this issue ?