Q I've just bought a new LCD monitor as a replacement for my old CRT. My Nvidia video card has two outputs - so is it possible to connect both monitors to the card and expand my KDE desktop to fill both of them? I'm using Gentoo 2006.1 with an Nvidia FX5200 video card.
A The answer is yes. There is a standard way of combining two screens as a single X display, called Xinerama. This is normally used with two graphics cards, but the Nvidia drivers contain a feature called TwinView that lets you display two screens from one card, one on each monitor output, while remaining compatible with Xinerama. Enabling TwinView (and Xinerama) is simple, assuming you're using the Nvidia drivers and not the open source nv driver. First emerge nvidia-drivers and make sure X is running on the Nvidia drivers - the most obvious indication is the Nvidia logo that pops up when X starts.
Next run nvidia-settings from a root terminal. This is a separate package on Gentoo, so you'll need to emerge it if you haven't already. Select X Server Display Configuration from the list on the left and you should see both displays, although one may be marked disabled. If one display isn't available, click on the Detect Displays button, select each display in turn and pick the correct resolution. It's best if both give the same resolution, but any Xinerama-aware window manager can handle different sized displays. Now set the Position for each screen. You can do this with absolute positioning for maximum control, but it's usually best to set one display to Right Of the other and the opposite for the other display. Click on the Save To X Configuration File button, log out and restart X. You should now have a desktop that spans two monitors, but it may need some tweaking. Make sure all applications are built with Xinerama support. If you don't already have xinerama in your USE flags, edit /etc/make.conf and add it, then rebuild all affected packages with:
emerge --update --deep --newuse --ask world
This may take a while, but when it is finished you can restart KDE and begin tuning it to suit your tastes. For example, the desktop can have a single, wide wallpaper or different ones for each monitor. Or the Kicker panel can be on a single monitor or stretched across both. The Multiple Monitors section of the Desktop settings allows you to set how windows behave and which is the default display for opening new windows. Pick your LCD monitor here. A useful feature is the Advanced > Special Window Settings menu option available when right-clicking a window's title bar. This lets you override default window manager behaviour for specific windows or applications. It's useful with a single display but even more so with dual displays, especially as it can force specific windows or applications to open in a particular position. For example, I get Gimp to open its toolbox on one display while opening the images on the other, so I can use a full screen window to edit an image without obscuring the toolbox.