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#1 2014-03-03 09:30:23

LoWang
Member
Registered: 2014-02-25
Posts: 17

multiple displays - strange gap between

Hello, this is something I have not seen in any other system. I have laptop and external monitor and I have it set as extended desktop. But when I move some window to the side it just keeps disappearing but does not appear on the next monitor. Almost when I have the whole window outside of the current display it starts appearing on the second monitor. It looks like xfce somehow detects that I have like 20cm gap between monitors and does not show the window in there :-) But I don't see any settings to change this.

And what is even more funny is that new windows seem to appear right in this gap and when it is small I see only a tiny part of it and almost don't notice it is there at all :-]

Last edited by LoWang (2014-03-03 10:12:58)

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#2 2014-03-03 11:19:23

ToZ
Moderator
From: Toronto, Canada
Registered: 2011-06-02
Posts: 1,036

Re: multiple displays - strange gap between

Which distro and what version of Xfce are you using?
How did you extend the desktop?
What are the actual physical resolutions of your laptop and external screens and what is the results of:

xrandr -q

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#3 2014-03-03 14:19:53

LoWang
Member
Registered: 2014-02-25
Posts: 17

Re: multiple displays - strange gap between

vitas@vitas-ThinkPad-T420:~$ xrandr -q
Screen 0: minimum 320 x 200, current 4544 x 1200, maximum 8192 x 8192
LVDS1 connected 1600x900+2944+0 (normal left inverted right x axis y axis) 310mm x 174mm
   1600x900       60.0*+
   1440x900       59.9  
   1360x768       59.8     60.0  
   1152x864       60.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 474mm x 296mm
   1920x1200      60.0*+
   1600x1200      60.0  
   1680x1050      60.0  
   1280x1024      75.0     60.0  
   1440x900       75.0     59.9  
   1024x768       75.1     70.1     60.0  
   800x600        72.2     75.0     60.3  
   640x480        72.8     75.0     60.0  
   720x400        70.1  
vitas@vitas-ThinkPad-T420:~$ uname -a
Linux vitas-ThinkPad-T420 3.5.0-46-generic #70-Ubuntu SMP Wed Jan 8 18:40:46 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
vitas@vitas-ThinkPad-T420:~$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 12.10
Release:	12.10
Codename:	quantal

xfce 4.10

It seems xfce does not have the extended display functionality by default (why?!), so I did this to add it
http://www.webupd8.org/2012/11/how-to-u … buntu.html

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#4 2014-03-03 15:02:02

ToZ
Moderator
From: Toronto, Canada
Registered: 2011-06-02
Posts: 1,036

Re: multiple displays - strange gap between

I can't comment on that version of the display manager that you are using since I don't have it here in my install. I understand though that its coming in the newer version of Xfce.

If you look at the results of your xrandr command, you have two displays:
- LVDS1 at 1600x900+2944+0
- VGA1 at 1920x1200+0+0

You should have a maximum horizontal resolution of 3520 (1600 + 1920) but your system is set up for 4544 ("current 4544 x 1200"). The VGA display (left)  has a horizontal resolution of 1920 but the LVDS1 display (right) starts at 2944 ("1600x900+2944+0") - hence the gap.

Again, I'm not sure what the utility is doing to create this.

Can you try just using xrandr to create the extension to see if it works? Use these commands (first one turns off the external display and the second one turns it back on and sets up the extension):

xrandr --output VGA1 --off
xrandr --output VGA1 --auto --left-of LVDS1

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#5 2014-03-03 17:00:38

LoWang
Member
Registered: 2014-02-25
Posts: 17

Re: multiple displays - strange gap between

nice, that fixed it! I hope it will work after system restart too smile

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#6 2014-03-03 18:50:48

ToZ
Moderator
From: Toronto, Canada
Registered: 2011-06-02
Posts: 1,036

Re: multiple displays - strange gap between

It won't, you have to manually enter it every time.

Here is an askubuntu answer on how to make it permanent using either a custom xorg.conf file (first answer) or using lightdm's display-setup-script option (second answer).

EDIT: Note, you'll only need to use the second command of the set above if using the lightdm solution:

xrandr --output VGA1 --auto --left-of LVDS1

...the first one is redundant if adding it to the startup scripts / configuration files.

Last edited by ToZ (2014-03-03 18:53:05)

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#7 2014-03-04 09:13:04

LoWang
Member
Registered: 2014-02-25
Posts: 17

Re: multiple displays - strange gap between

believe it or not, yesterday I restarted the pc into windows on another drive and today I started it back to Ubuntu and it stays OK! I did not need to tweak anything again.

vitas@vitas-ThinkPad-T420:~$ xrandr -q
Screen 0: minimum 320 x 200, current 3520 x 1200, maximum 8192 x 8192
LVDS2 connected 1600x900+1920+0 (normal left inverted right x axis y axis) 310mm x 174mm
   1600x900       60.0*+
   1440x900       59.9  
   1360x768       59.8     60.0  
   1152x864       60.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA2 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 474mm x 296mm
   1920x1200      60.0*+
   1600x1200      60.0  
   1680x1050      60.0  
   1280x1024      75.0     60.0  
   1440x900       75.0     59.9  
   1024x768       75.1     70.1     60.0  
   800x600        72.2     75.0     60.3  
   640x480        72.8     75.0     60.0  
   720x400        70.1  

Last edited by LoWang (2014-03-04 09:13:44)

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#8 2014-03-04 11:35:24

ToZ
Moderator
From: Toronto, Canada
Registered: 2011-06-02
Posts: 1,036

Re: multiple displays - strange gap between

Yes, the results of xrandr now look correct. You may have found a bug in that utility.

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#9 2014-03-05 07:23:19

LoWang
Member
Registered: 2014-02-25
Posts: 17

Re: multiple displays - strange gap between

and now I have different problem. When I disconnect the external display panel moves to thinkpad screen, BUT it does not fit, so I cannot see and click on the applications menu.
It looks it just gets stretched to the right over the thinkpad screen, but the left side of it stays in the void of the disconnected external display.

Screen 0: minimum 320 x 200, current 3520 x 1200, maximum 8192 x 8192
LVDS2 connected 1600x900+1920+0 (normal left inverted right x axis y axis) 310mm x 174mm
   1600x900       60.0*+
   1440x900       59.9  
   1360x768       59.8     60.0  
   1152x864       60.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9 
VGA2 disconnected 1920x1200+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
  1920x1200 (0x74)  154.0MHz
        h: width  1920 start 1968 end 2000 total 2080 skew    0 clock   74.0KHz
        v: height 1200 start 1203 end 1209 total 1235           clock   60.0Hz

I guess I want too much :-\

Last edited by LoWang (2014-03-05 07:27:15)

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#10 2014-03-05 11:09:10

ToZ
Moderator
From: Toronto, Canada
Registered: 2011-06-02
Posts: 1,036

Re: multiple displays - strange gap between

Try running:

xrandr --output VGA2 --off

...to see if that works.

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#11 2014-03-06 12:10:34

LoWang
Member
Registered: 2014-02-25
Posts: 17

Re: multiple displays - strange gap between

so now I wanted to test it and guess what - after disconnecting the external monitor it all properly moved to a laptop screen with everything visible! Unfortunately after connecting the monitor back it did not extend and monitor remained off, so now I have to go to settings / display and check it to be used everytime I connect the monitor back. Strange that last time it was switching back and forth automatically but with the problem mentioned above :-]
Why can't I just press win+P to set everything like in windows 7? big_smile

Last edited by LoWang (2014-03-06 12:12:13)

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#12 2014-03-06 13:21:38

ToZ
Moderator
From: Toronto, Canada
Registered: 2011-06-02
Posts: 1,036

Re: multiple displays - strange gap between

What happens if you run:

xfce4-display-settings -m

Does it pop-up a dialog box that lets you choose how to arrange your dual-monitor setups? If so, just add that command to the Win+P shortcut via Settings Manager -> Keyboard -> Application shortcuts.

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