Multiple monitors as cloned desktop windows

Happens for me too - very annoying. I used to have 5 workspaces in a row under Ubuntu 10.04. However, I did find that putting 4 workspaces in 2 rows stops the windows from jumping around. It's harder to click on a workspace but that's my fix for now.

I found a related question on Ask Ubuntu which sort of did the trick for me. Instructions for the whole process, including creating the "gap" between monitors (works at least on Ubuntu 14.04):

• Find out the current total screen size (assuming there's currently no virtual gap between monitors):
  $ xrandr | grep Screen Screen 0: minimum 320 x 200, current2048 x 1280, maximum 32767 x 32767
• Add the desired gap size in pixels to the width (first value displayed after current – in my case, 2048). I chose a gap of 136 pixels, so I'd have a new screen width of 2184.
• Set the new screen size:
  xrandr --fb 2184x1280
• Find out the display name of your right monitor:
  $ xrandr | grep ^[^\(]*right HDMI3connected 1024x1280+1024+0 right (normal left inverted right x axis y axis) 376mm x 301mm
• Virtually move the right monitor further to the right to create the gap. Add your gap size to the third number displayed by the above command (highlighted in bold). In my example, this is 1024+136=1160:
  xrandr --output HDMI3 --pos 1160x0

Now, make Compiz handle the whole area as one single screen

• Start CompizConfig Settings Manager (installable with sudo apt-get install compizconfig-settings-manager)
• Go to "General Options" plugin (e.g. type this in search box)
• Select tab "Display Settings"
• Uncheck "Detect Outputs"
• If this doesn't already do the trick, right click on each line listed under "Outputs", select "Edit" and delete their content.

When maximizing a window, it will now stretch both monitors. Fullscreen will also stretch both monitors.

Clearly, this isn't ideal, as most of the time it is desirable that maximized windows fill a single monitor. This means, the "Detect Outputs" Compiz option will have to be checked and unchecked depending on what behavior is currently desired.

A note to user with non-English locale: If you can't find the CompizConfig plugin and setting because you don't know how their names were translated, start CompizConfig like so:

LANG=C ccsm