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I have an HP Pavilion TouchSmart laptop running Ubuntu 14.04.1

I usually connect a second display via HDMI which worked fine until today. I can connect the display fine and everything auto-configures properly. However, disconnecting the display has no effect most of the times - the desktop stays in extended mode and I can move the mouse / windows off the screen to where the second screen used to be. There is no short black-out that usually indicates a screen has been (dis)connected.

I found out that just opening display settings under Ubuntu system settings fixes the issue and the system detects that I have in fact disconnected the second screen. The same happens when running xrandr from terminal - I'm using this as a workaround at the moment.

There is one more strange thing - normally Super+P toggles between extended, clone, first screen only and second screen only modes. This works fine for me when the second screen is actually connected. After disconnecting the screen (and when the system doesn't register the disconnection), using this shortcut breaks all video output, I see fragments of the desktop on laptop screen, nothing seems to fix this problem except hard reset.

I also have Windows 8.1 installed (dual boot) and everything works fine there, so it's not a hardware problem. The laptop has switchable graphic cards (Intel Haswell integrated CPU + AMD Radeon 8670M). I am using the default drivers and have never installed the proprietary ones.

[Edit - xrandr output]

HDMI Connected and working

Screen 0: minimum 320 x 200, current 3286 x 1080, maximum 32767 x 32767
eDP1 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 309mm x 173mm
   1366x768       60.1*+   40.0  
   1360x768       59.8     60.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
HDMI1 connected 1920x1080+1366+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080      60.0*+
   1680x1050      59.9  
   1600x900       60.0  
   1280x1024      75.0     60.0  
   1280x960       60.0  
   1152x864       75.0  
   1280x720       60.0  
   1152x720       60.0  
   1024x768       75.1     60.0  
   832x624        74.6  
   800x600        75.0     60.3  
   640x480        75.0     60.0  
   720x400        70.1  
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

HDMI Properly disconnected

Screen 0: minimum 320 x 200, current 1366 x 768, maximum 32767 x 32767
eDP1 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 309mm x 173mm
   1366x768       60.1*+   40.0  
   1360x768       59.8     60.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
HDMI1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

HDMI Disconnected but still being detected as connected (running xrandr produces this and then fixes the problem). Notice the strange output at the end.

Screen 0: minimum 320 x 200, current 3286 x 1080, maximum 32767 x 32767
eDP1 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 309mm x 173mm
   1366x768       60.1*+   40.0  
   1360x768       59.8     60.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
HDMI1 disconnected 1920x1080+1366+0 (normal left inverted right x axis y axis) 0mm x 0mm
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
  1920x1080 (0x68)  148.5MHz
        h: width  1920 start 2008 end 2052 total 2200 skew    0 clock   67.5KHz
        v: height 1080 start 1084 end 1089 total 1125           clock   60.0Hz

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