Arch Linux

jchillerup

Member

From: Denmark

Registered: 2011-08-10

Posts: 19

Matrox DualHead2Go and XrandR

Hello,

Recently I acquired a Matrox DualHead2Go which essentially is a device that allows two monitors to be connected to one port by claiming that it is one very wide monitor. In my configuration I want two external 1920x1080 displays connected to my laptop. I want the two external monitors to act as independently of each other as possible, i.e. I should be able to maximize windows onto one monitor, and not spanning the two external monitors as it is now. I'm using XFCE for what it's worth and using a tiling window manager on top of that would not really be what I want to achieve, namely to have the monitors appear as two logical displays in XrandR.

xrandr as run on the command-line correctly shows the following:

Screen 0: minimum 8 x 8, current 5440 x 1080, maximum 32767 x 32767
LVDS1 connected 1600x900+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   1600x900      59.97*+
   1024x768      60.00  
   800x600       60.32    56.25  
   640x480       59.94  
VGA1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
DP1 connected 3840x1080+1600+0 (normal left inverted right x axis y axis) 255mm x 255mm
   3840x1080     59.88*+
   2560x1024     59.88  
   1920x1080     60.00    59.94    59.88  
   1920x1080i    60.00    59.94  
   1680x1050     59.88  
   1600x900      59.98  
   1280x1024     75.02    59.88  
   1440x900      59.88  
   1280x800      59.81  
   1152x864      75.00  
   1600x600      59.88  
   1280x720      59.97    60.00    59.94  
   1024x768      75.08    70.07    60.00  
   1440x480      60.00    59.94  
   832x624       74.55  
   800x600       72.19    75.00    60.32    59.88    56.25  
   720x480       60.00    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94  
   720x400       70.08  
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

The DP1 display measures 2x 1920-by-1080 pixels, and I can use the two monitors all right. The problems arise when I maximize a window, watch videos in full screen or try to configure the XFCE panel because it perceives my two monitors as one super-wide one.

I think the solution has something to do with instantiating two 1920x1080 virtual displays and somehow imposing those on the DP1 display, but I don't know how. The other threads on this BBS concerning this problem are from the Xinerama ages and I would really prefer an XrandR-based solution. Thanks a lot!

Last edited by jchillerup (2014-06-27 11:10:32)

Rexilion

Member

Registered: 2013-12-23

Posts: 784

Re: Matrox DualHead2Go and XrandR

I think that Xinerama will be your only way out. Xorg is 'seeing' one big monitor and that needs to be dealth with. I have not seen such options in the xrandr manpage.

However, post #3 here mentions something like this:

Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 24
Option "Coolbits" "1"
Option "NoLogo" "True"
Option "CursorShadow" "True"
Option "RenderAccel" "True"
Option "AddARGBGLXVisuals" "True"
Option "ConnectToAcpid" "False"
Option "TwinView" "True"
Option "TwinviewXineramaInfo" "False"
Option "DynamicTwinView" "False"
Option "MetaModes" "1600x1200,3200x1200"
Option "SecondMonitorHorizSync" "31-80"
Option "SecondMonitorVertRefresh" "60-60"
SubSection "Display"
Viewport 0 0
Depth 24
Modes "1600x1200"
EndSubSection
EndSection

Do you see the 1600x1200? That is with a 4800x1200 screen. Maybe  that is the key.

---

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MoonSwan

Member

From: Great White North

Registered: 2008-01-23

Posts: 881

Re: Matrox DualHead2Go and XrandR

Instantiating two separate "monitors" is likely the only way to do this as you've surmised.  What I can suggest, however, is to look at the wiki for starting X as two separate processes.  With an Nvidia card I know it isn't that difficult.

I did some searching for you and found several Arch threads (see third hit down on the page for numerous forum posts):  https://www.google.ca/search?q=running+ … 8geLzYG4Bw

jchillerup

Member

From: Denmark

Registered: 2011-08-10

Posts: 19

Re: Matrox DualHead2Go and XrandR

I think that Xinerama will be your only way out.

Then, I take it, FakeXinerama would be a better fit.