Wanted to put down some useful things I have learnt about dual-screening in Ubuntu since I moved over to working under Linux full-time at work (and thus using a dual-screen environment more consistently).
1. The Intel driver for their gfx chips can’t do 3D on a combined screen size of wider or higher than 2048. So, if like me, you want to have your 1440 to the left of your 1280 monitor, with a total size of 2720, then you can’t have Compiz desktop effects enabled. (I think the solution would be to have them on top of each other, which would be <2048, but I haven’t tried that)
2. The guide here has some handy stuff about setting up xrandr to detect at login whether or not you have 2 screens connected – works great for me.
3. GNOME by default will always put it’s panels on the external monitor in a dual-screen setup. However, I discovered that you can tweak this by editing gconf when you login, adding a couple of lines to the ones added in step (2). (In file /etc/X11/Xsession.d/45custom_xrandr-settings:
if [ $? -eq 0 ]; then
xrandr --output $INTERNAL_OUTPUT --auto --output $EXTERNAL_OUTPUT --auto $EXTERNAL_LOCATION
gconftool-2 --type int --set /apps/panel/toplevels/bottom_panel_screen0/monitor 1
gconftool-2 --type int --set /apps/panel/toplevels/top_panel_screen0/monitor 1
else
xrandr --output $INTERNAL_OUTPUT --auto --output $EXTERNAL_OUTPUT --off
fi
4. If you have your virtual screen size set up appropriately, then the System -> Preferences -> Screen Resolution dialog also seems to work pretty well for times when you’re adding a projector on (although you’ll need to drag panels across from the projector as per (3) – haven’t worked out where I can add the gconf changes to make this happen automagically)
Anyway – still a work in progress. This was all done on Hardy – Intrepid upgrade on the to-do list once the relevant packages for my work software are available. The screen handling stuff may well be better in Intrepid.
mrBen