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[xcolour <matthew.j.singleton@xxxxxxxxx>]

Public bug reported:

Binary package hint: xserver-xorg-video-ati

I have a dual monitor setup and I am arranging my monitors with xrandr.
My configuration has one monitor in portrait and one in landscape.  When
I rotate the monitor to portrait mode, I end up with the screens being
offset by one pixel.  The attached screenshot should make it clearer.
If you look at the screenshot, you'll see that column 1679 is the
rightmost edge of my left screen, as the panel ends there (this is
correct).  The problem is that column 1679 is displayed on the right
monitor.  Additionally, column 2729 (the far right coloumn) is not
displayed on the right monitor at all.  The display ends at column 2728.
The screens are not overlapping.  I can prove this by counting the
number of pixels displayed on each side of the split.  There are no
repeats.

The oddest part is that if I rotate my monitor to the right rather than
the left with xrandr, the problem disappears!  It's not a viable option
for me, though, because my monitor stand only rotates one way.

The xrandr commands that get me here are:
$ xrandr --output DVI-1 --rotate left
$ xrandr --output DVI-0 --pos 0x0
$ xrandr --output DVI-1 --pos 1680x0

So, how did I get here?

I have two identical Dell 2007WFPb monitors.

$ lspci | grep VGA
01:00.0 VGA compatible controller: ATI Technologies Inc RV516 [Radeon X1300/X1550 Series]

$ cat /etc/X11/xorg.conf
Section "Monitor"
	Identifier	"Left Monitor"
EndSection

Section "Monitor"
	Identifier	"Right Monitor"
        Option          "LeftOf" "Left Monitor"
        Option          "Rotation" "left"
EndSection

Section "Screen"
	Identifier	"Default Screen"
	Monitor		"Left Monitor"
	Monitor		"Right Monitor"
	Device		"Configured Video Device"
	SubSection "Display"
		Virtual	3361 3361
	EndSubSection
EndSection

Section "Device"
	Identifier	"Configured Video Device"
        Option "Monitor-DVI-1" "Left Monitor"
        Option "Monitor-DVI-0" "Right Monitor"
EndSection

$ xrandr 
Screen 0: minimum 320 x 200, current 2730 x 1680, maximum 3361 x 3361
DVI-1 connected 1050x1680+1680+0 left (normal left inverted right x axis y axis) 434mm x 270mm
   1680x1050      59.9*+
   1280x1024      75.0     60.0  
   1152x864       75.0  
   1024x768       75.0     60.0  
   800x600        75.0     60.3  
   640x480        75.0     59.9  
   720x400        70.1  
DVI-0 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 434mm x 270mm
   1680x1050      59.9*+
   1280x1024      75.0     60.0  
   1152x864       75.0  
   1024x768       75.0     60.0  
   800x600        75.0     60.3  
   640x480        75.0     59.9  
   720x400        70.1  

$ lsb_release -rd
Description:	Ubuntu 9.04
Release:	9.04

$ apt-cache policy xserver-xorg-video-ati
xserver-xorg-video-ati:
  Installed: 1:6.12.1-0ubuntu2
  Candidate: 1:6.12.1-0ubuntu2
  Version table:
 *** 1:6.12.1-0ubuntu2 0
        500 http://mirrors.kernel.org jaunty/main Packages
        100 /var/lib/dpkg/status

** Affects: xserver-xorg-video-ati (Ubuntu)
     Importance: Undecided
         Status: New

-- 
xrandr rotate left is off by one pixel with open source ati driver
https://bugs.launchpad.net/bugs/418668
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