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My laptop has Intel Mobile GM965/GL960 integrated graphic controller and the screen size is 1280x800. When I plug another LCD (ThinkVision 22") the upper half of the laptop screen becomes black.

I can see: - the top panel (on both monitors) - the bottom size of the laptop screen with all windows and stuff - the mouse cursor when it goes over the upper black half of the laptop screen and everywhere on the second screen

I cannot see: - anything else (except for the mouse cursor) in the upper half of the laptop screen - anything (except for the top panel and mouse cursor) on the second screen

I used Ubuntu 10.10 before with the same hardware and the same two monitors -- everything worked fine. But now I can't use the other monitor. Tried to search for a solution -- no luck.

Some additional observations: - If I change the resolution on the other screen to lower settings, then the black part shrinks vertically (it is still there, though) - After I unplug the second monitor, some windows shift, for example those extended to a half of screen etc.

Any links or ideas are very appreciated. Thanks.

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2  
Have you tried pressing alt-F2 and running "unity --replace"? –  Ethan May 6 '11 at 23:03
    
Thanks for reply. No, I haven't. But I did restart the whole thing several times and tried with slightly different options. How this exactly may help? –  Vadim May 6 '11 at 23:54
1  
Same graphics card (on a lenovo T61), same issue here - running unity --replace worked for me - no need to log out/log back in. –  Mark May 13 '11 at 13:02
    
Yes, it worked, thanks. I just asked to make sure what exactly it does and was waiting for a feedback. I also read somewhere that "unity --replace" is sometimes buggy and may not preserve some settings etc. Anyway, voted the comments of both of you up. This is a better alternative to logging out/in. –  Vadim May 14 '11 at 4:44
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3 Answers

up vote 3 down vote accepted

I have resolved the issue, though still think that is a bug.

So, I connected the second monitor, it connected black and half of the laptop screen went black as well. But I left it as it is, just restarted the whole system, and it worked: after the restart both displays shows well. I can disconnect and reconnect the second one, and it works.

P.S. Just tried everything to make it work and found this way...

Edit: In fact, it is enough to just log off/log in with the connected second monitor, and it works.

Edit-2: See also the comments above. Basically, I think the best way is to connect the monitor before logging in, and if it does not work try Alt+F2 and "unity --replace" as an alternative, otherwise log out/in.

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Yep, old compiz bug, has been bothering me for years. Alt-F2 unity ought to be sufficient to fix it (--replace is the default action). –  Marius Gedminas Jun 13 '11 at 21:39
    
Also, please mark your answer as accepted, so people can see it was resolved. –  Marius Gedminas Jun 13 '11 at 21:41
    
Ok, as long as someone else asks me to mark my own answer... ;) Marked as resolved. –  Vadim Jun 13 '11 at 21:52
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I think that

if you use 3D acceleration (Unity) for this graphics card, the dual head setup should fit in a 2048x2048 pixels box.

You can orient the screens one on top of the other in order to test this theory.

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Thanks for reply. Just tried -- no luck. Even worse. So, I put 1920x1200 below 1280x800 -- total of 1920x2000. Now, when I switch to dual-monitor, the whole laptop screen becomes unresponsive (except for the panel). –  Vadim May 6 '11 at 23:55
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Just go to the monitor configurations and move the right monitor to the left (just drag the monitor)... This works for me. Now I can use external screen at 1980x1080 suing HDMI

Regards Oscar Santiago, Chile.

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Thanks. I have already tried the solution by user4124 with no luck, however, I tried to put the other screen below (to make the whole desktop fit 2000x2000) but did not try to move it to the left of the main laptop screen. Will try next time. –  Vadim Jun 13 '11 at 19:24
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