2010-03-15 18:04:32 -04:00
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The multi-monitor situation
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===========================
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Michael Stapelberg <michael+i3@stapelberg.de>
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March 2010
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2010-03-20 20:50:10 -04:00
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…or: oh no, I have an nVidia graphics card!
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2010-03-15 18:04:32 -04:00
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== The quick fix
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2010-03-20 20:50:10 -04:00
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If you are using the nVidia binary graphics driver (also known as 'blob')
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you need to use the +--force-xinerama+ flag (in your .xsession) when starting
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i3, like so:
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2010-03-15 18:04:32 -04:00
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.Example:
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----------------------------------------------
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2010-03-20 20:50:10 -04:00
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exec i3 --force-xinerama -V >>~/.i3/i3log 2>&1
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2010-03-15 18:04:32 -04:00
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----------------------------------------------
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== The explanation
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Starting with version 3.ε, i3 uses the RandR (Rotate and Resize) API instead
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2010-03-20 20:50:10 -04:00
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of Xinerama. The reason for this, is that RandR provides more information
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2010-03-15 18:04:32 -04:00
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about your outputs and connected screens than Xinerama does. To be specific,
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the code which handled on-the-fly screen reconfiguration (meaning without
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restarting the X server) was a very messy heuristic and most of the time did
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not work correctly -- that is just not possible with the little information
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Xinerama offers (just a list of screen resolutions, no identifiers for the
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screens or any additional information). Xinerama simply was not designed
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for dynamic configuration.
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2010-03-20 20:50:10 -04:00
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So RandR came along, as a more powerful alternative (RandR 1.2 to be specific).
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2010-03-15 18:04:32 -04:00
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It offers all of Xinerama’s possibilities and lots more. Using the RandR API
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made our code much more robust and clean. Also, you can now reliably assign
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workspaces to output names instead of some rather unreliable screen identifier
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(position inside the list of screens, which could change, and so on…).
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2010-03-20 20:50:10 -04:00
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As RandR has been around for about three years as of this writing, it seemed
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like a very good idea to us, and it still is a very good one. What we did not
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expect, however, was the nVidia binary driver. It still does not support RandR
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(as of March 2010), even though nVidia has announced that it will support RandR
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eventually. What does this mean for you, if you are stuck with the binary
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driver for some reason (say the free drivers don’t work with your card)? First
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of all, you are stuck with TwinView and cannot use +xrandr+. While this ruins
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the user experience, the more grave problem is that the nVidia driver not only
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does not support dynamic configuration using RandR, it also does not expose
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correct multi-monitor information via the RandR API. So, in some setups, i3
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will not find any screens; in others, it will find one large screen which
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actually contains both of your physical screens (but it will not know that
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these are two screens).
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2010-03-15 18:04:32 -04:00
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For this very reason, we decided to implement the following workaround: As
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long as the nVidia driver does not support RandR, an option called
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+--force-xinerama+ is available in i3. This option gets the list of screens
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2010-03-20 20:50:10 -04:00
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*once* when starting, and never updates it. As the nVidia driver cannot do
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2010-03-15 18:04:32 -04:00
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dynamic configuration anyways, this is not a big deal.
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== See also
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For more information on how to use multi-monitor setups, see the i3 User’s
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Guide.
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