I have the same problem (see: attachment), my lspci command outputs
"00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series
Chipset Integrated Graphics Controller (rev 07)". I search the Internet
and found
(http://www.thinkwiki.org/wiki/Xorg_RandR_1.2#the_Virtual_screen) that
my frame buffer can not exceed 2048x2048. So these steps I tried to
confirm this:
Note: The attached screen-shot is made with "Laptop" on 1280x800 and
"Acer" on 1024x768 with Compiz enabled.
1. I started with Compiz disabled (i assume this disabled DRI). All
problems disappear except the problem of having my cursor disappear when
i place it at the bottom of my "Acer" monitor. This can be seen as a
black bar right from the workspace switcher (see: screen-shot).
2. Next i go to the "Visual Effects" en switch the radio button from
"None" to "Normal". This causes the following error: "Desktop effects
could not be enabled". The radio button jumps back to "None".
3. I use "Display Preferences" (xrandr gui) to set "Acer" to 640x480.
After i found my cursor somewhere in the borders of my Acer screen I
enabled Compiz by repeating step 2. Only this time Compiz successfully
enabled. The difference between this and the previous step is that in
the previous step the frame buffer was exceeded horizontal with
(1280+1024)-2048 = 256 pixels (which matches exact with my screen dump).
4. Now when I set the "Acer" screen back to 1024x768 I get the problem
described here and in my screen-shot. To fix this I disabled Compiz with
the "Visual Effects" GUI. If u want u can jump to step 1 to repeat the
procedure again.
My "/etc/X11/xorg.conf":
--------------------------------------------------
Section "Monitor"
Identifier "Configured Monitor"
EndSection
Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
SubSection "Display"
Virtual 2560 1024
EndSubSection
EndSection
Section "Device"
Identifier "Configured Video Device"
EndSection
** Attachment added: "Intel Mobile 4 Series.png"
http://launchpadlibrarian.net/30499666/Intel%20Mobile%204%20Series.png
--
[GM45] Dual screen is not properly configured, size and refresh problem (UXA
bug)
https://bugs.launchpad.net/bugs/378482
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which is subscribed to xserver-xorg-video-intel in ubuntu.
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