[SOLVED] Xinerama multihead setup with nVidia 9800 GT

Snark1994 · 01-30-2011, 10:14 AM

Hiya all,

Recently installed Slackware, and now trying to get my two monitors working nicely. After much hair-tearing I've got Xinerama set up so that each monitor displays separate information.

I'm using an nVidia 9800 GT dual-headed graphics card. This is my xorg.conf file:

Code:

Section "ServerFlags"
	Option 	"Xinerama" "ON"
EndSection

Section "ServerLayout"
	Identifier     "Josh Xinerama Configured"
	Screen      0  "Screen0" 0 0
	Screen	1 "Screen1" RightOf "Screen0"
#Two input device lines removed
EndSection


Section "Files"
	ModulePath   "/usr/lib64/xorg/modules"
#11 fontpath lines removed
EndSection

Section "Module"
	Load  "dbe"
	Load  "dri2"
	Load  "glx"
	Load  "dri"
	Load  "extmod"
	SubSection "extmod"
		Option "omit xfree86-dga"
	EndSubSection
EndSection

#2 Input device sections removed

Section "Monitor"
	Identifier   "left"
	VendorName   "Samsung"
	ModelName    "SyncMaster 720N"
	Option "dpms"
EndSection

Section "Monitor"
	Identifier "right"
	VendorName "Compaq"
	ModelName "CQ1859s"
	Option "dpms"
EndSection

Section "Device"
	Identifier  "Nvidia0"
	Driver      "nvidia"
	VendorName  "Unknown Vendor"
	BoardName   "Unknown Board"
	BusID       "PCI:1:0:0"
	Option "HWCursor" "On"
	Screen 1
EndSection

Section "Device"
	Identifier  "Nvidia1"
	Driver      "nvidia"
	VendorName  "Unknown Vendor"
	BoardName   "Unknown Board"
	BusID       "PCI:1:0:0"
	Option "HWCursor" "On"
	Screen 0
EndSection

Section "Screen"
	Identifier "Screen0"
	Device     "Nvidia1"
	Monitor    "left"
	SubSection "Display"
		Viewport   0 0
		Depth     1
	EndSubSection
	#Many "Display" subsections removed, all identical to above
        #except for "Depth" value
EndSection

Section "Screen"
	Identifier "Screen1"
	Device     "Nvidia0"
	Monitor    "right"
	SubSection "Display"
		Viewport   0 0
		Depth     1
	EndSubSection
	#Many "Display" subsections removed, all identical to above
        #except for "Depth" value
EndSection

My current problem is as follows:

(1) When I have the "ServerLayout" section like this:

Code:

Screen      0  "Screen0" 0 0
Screen	1 "Screen1" RightOf "Screen0"

then everything works, but to get the mouse from the right-hand screen to the left-hand screen, you need to go over the RIGHT edge, not the left. Essentially, the physical right monitor is being treated as the virtual left monitor.

(2) If I have the ServerLayout section like this:

Code:

Screen      0  "Screen0" 0 0
Screen	1 "Screen1" LeftOf "Screen0"

then the mouse is stuck on the right screen. It seems to recognise that the physical right monitor is the virtual right monitor, but if you try to move off the left side of the screen, it appears on the right side of the same screen. This seems to be similar to the bug described here, but that's meant to be fixed in v1.2.3 and I have v1.5.0 (according to pkgtool).

Any hints? Obviously, solving either problem would considered a solution

I have also considered physically swapping the monitors, but then I would have to edit all the other OSes I use to know about the change, and also on principle I feel I should work out why it's not working... Thanks

serafean · 01-30-2011, 01:30 PM

Hi, what I think is happening is that screen0 is at position 0 0, and you put screen1 at its left, effectively making your entire display start at -Screen1XSize 0. My idea is to either make Screen1 placed at 0 0 :

Code:

Screen      0  "Screen1" 0 0
Screen  1 "Screen0" RightOf "Screen1"

But I haven't tried this out, so I can't guarantee the result (although I find this to be the correct and "elegant" way).
And second : move screen0 to the X-size end of screen1. ie if your screen1 has the resolution of 1024x768, make screen0 start at 1024 0 :

Code:

Screen      0  "Screen0" 1024 0
Screen  1 "Screen1" LeftOf "Screen0"

I have written an article in my LQ blog about my special X setup, you might try reading it if it helps you in any way (and I'd love to get some feedback

)

Serafean

Snark1994 · 01-31-2011, 05:54 PM

Ahahahaha... It drove me half insane, but I got there in the end... -.-

Thank you Serafean, I tried your first suggestion and thought it didn't work because X complained about a lack of screens. I copied over my Ubuntu configuration (to no avail) and did something strange which I forget, that also didn't work. Finally, I went back to your suggestion and realised that if I only made the changes in the ServerLayout section I was left with an inconsistent file - the "Screen 0" option set in my driver didn't match with the corresponding "Screen 1 blah blah" line in my ServerLayout section. So all I did was use Serafean's first solution and propagated the changes to the rest of the file to make it all consistent:

Code:

Section "ServerLayout"
    Screen  0  "Screen1" 0 0
    Screen  1  "Screen0" RightOf "Screen1"
EndSection

Section "Device"
    Identifier "Nvidia0"
    Screen 0
EndSection

Section "Device"
    Identifier "Nvidia1"
    Screen 1
EndSection

Section "Screen"
    Identifier "Screen0"
    Device "Nvidia1"
    Monitor "left"
EndSection

Section "Screen"
    Identifier "Screen1"
    Device "Nvidia0"
    Monitor "right"
EndSection

...missing out any irrelevant lines. So thanks again to Serafean