Hi guys, I haven't looked at app_server code in a long time, and I'm speaking from memory here. If I'm wrong feel free to correct me. We have spoken about invalidating (visible region calculation) only from one thread only - the poller thread. I will change that in the next days. We also spoken (me and DW long time ago), and designed app_server architecture in such a way, about multiple user support at the same time and/or across network. Although none of these will be available in R1, I think things should in conformance with the design. So, we decided RootLayer class for being the one responsible for showing the "Desktop" image - the image drawn on screen. Since we can have 2 users with 2 keyboards 2 mices and 2 monitors OR a working user and 2 working across network, I think RootLayer should also handle the input corespondent for each user. Currently the input code is part of Desktop class and this class has only one instance compared to RootLayer can have multiple instances. I'm telling you this, as I am preparing to integrate the new window manager I have written. Please reply quickly if you have something to say as I want to start making these changes from tomorrow. Thanks, Adi.