Since I got my 20" widescreen monitor in the summer, I discovered how bad
X's support for resizing displays is. I wanted to have the ability to
plug my laptop into the 20" display in the office and expand the desktop
to 1680x1050, or remove the 20" display and shrink the desktop back down
to the native resolution of 1024x768. It turns out that a number of
factors were stopping this, and the only way to do it would have been to
restart X. Because of this I ended up using the display at 1024x768 when
I did use it, but mostly I stayed on the sofa.
Then I heard about
xrandr 1.2, the all-singing all-dancing
revision of the X Resize and Rotate extension. Basically, it would solve
my problem, and as luck would have it my laptop has an Intel chipset and
the people hacking on it work at Intel. Yesterday after lots of poking I
finally made it all work for this. This involved a lot of poking and a
little black magic.
The first step is getting an X server new enough. First, you'll need to
update some X protocol headers. We'll start with the easy ones that have
had releases (grab the latest release you can find):
- xproto
- glproto
- inputproto
Then you'll need to update various other bits of X:
Once this is done and X still works, it's time to brave the perilous world
of git. If you've never used git before, it's quite simple for this. Go
to
the git browser and find
the module you want to check out. Click on it, and you'll see two URLs:
you want the
anongit one. Do
git clone [url], and then
if I've specified a branch other than master,
cd into the
directory and do
git checkout [branch]. For example:
git clone git://anongit.freedesktop.org/git/xorg/driver/xf86-video-intel
cd xf86-video-intel
git checkout modesetting
You'll need to grab:
- xorg/proto/x11proto
- xorg/proto/randrproto
- xorg/lib/libXrandr
- xorg/app/xrandr
- xorg/xserver (randr-1.2-for-server-1.2)
- xorg/driver/xf86-video-intel (modesetting)
Build it all in that order. The order is important as if you build the
Intel driver against randr 1.0 instead of 1.2, it won't do what you want.
By now you should have an X that looks no different. But...
$ xrandr
Screen 0: minimum 320 x 240, current 1024 x 768, maximum 1680 x 1050
VGA disconnected 0mm x 0mm
LVDS connected 1024x768+0+0 246mm x 185mm
1024x768 50.0 + 60.0* 40.0
800x600 60.3
640x480 60.0 59.9
TV disconnected 0mm x 0mm
Now that is clever. Here you can see that I don't have anything connected
via VGA, my LVDS (no idea what this stands for, but it means the laptop's
panel) has a preferred mode of 1024x768 (thats what the * means), and I
have nothing connected to the TV output (because Lenovo didn't wire it
up). Now if I plug something into the VGA and run
xrandr -s 0
(select default screen size), the external display should power on.
Xrandr doesn't try to be too clever, it will leave that to desktop
daemons, but by default it will try and make something appear on all of
the connected displays. In this case, my 20" TFT gets a clone of my
laptop panel, at 1024x768.
That is no good though, I want to turn off the laptop panel (as I'll be
shutting the laptop) and switch the external display to 1680x1050. This
is where the black magic starts... Currently the Intel driver cannot
resize the physical framebuffer in memory after X has started, so it
defaults to a framebuffer of 1200x1024 (IIRC). That isn't big enough to
hold 1680x1050. Also the Intel driver doesn't detect any modes from the
TFT. This may be Dell being stupid, or the EDID parser in the driver
being too restrictive, I don't know. Luckily we can still use modelines
in
xorg.conf so I added this:
Section "Monitor"
Identifier "Dell TFT"
# This is a standard modeline for 1680x1050 at 60Hz
Modeline "1680x1050" 149.00 1680 1760 1944 2280 1050 1050 1052 1089
EndSection
Section "Screen"
Identifier "Screen"
Device "Intel"
Monitor "Monitor"
# This says that when using a monitor on the output called VGA, use the
# settings in the monitor "Dell TFT"
Option "monitor-VGA" "Dell TFT"
DefaultDepth 24
SubSection "Display"
Depth 24
# This tells the screen to allocate a frame buffer up to
# 1680x1050.
Virtual 1680 1050
EndSubSection
EndSection
With this, everything just works. If I
xrandr with various
displays plugged in I can see what they support and can switch modes. To
make everything nice and easy I wrote a small script that I bound to an
unused function key:
if xrandr -q grep -q "VGA connected"; then
xrandr --output LVDS --off --output VGA --mode 1680x1050
else
xrandr --output VGA --off --output LVDS --mode 1024x768
fi
(thanks to Eric for pointing out that I don't need to use the hex values).
Simple! As you can see the new xrandr is
very powerful. If you
want to do Xinerama-style dual screen you can do that too: xrandr 1.2
encompasses that behaviour.
The final thing to point out is how glad I am that GNOME seems to handle
the screen resizing like this so nicely already. When the desktop shrinks
Metacity moves windows so they are visible, and when the desktop expands
the panel applets on the right stay on the right instead of sitting in the
middle. The script I run when I change screens does more than I pasted
here: it changes the wallpaper to match the aspect ratio, and also changes
the fonts.
I hope this has made sense, I know there are a few people out there who
were waiting for me to test this before they gave it a go. If anything is
too vague, leave a comment and I'll expand it. I should also mention that
I've got Ubuntu Edgy packages for everything here in
my repository.
NP: Animal Magic, Bonobo
