Display resolution issue on 12.04 with external display on laptop

[Colin Law]

On 28 May 2012 18:13, Liam Proven <lproven at gmail.com> wrote:
> On 28 May 2012 17:55, Chris Green <cl at isbd.net> wrote:
>> On Mon, May 28, 2012 at 05:22:28PM +0100, Liam Proven wrote:
>>> On 28 May 2012 11:50, Chris Green <cl at isbd.net> wrote:
>>> > We have just upgraded my wife's Dell Vostro v13 laptop from
>>> > 10.04 to 12.04, it all works OK except that it doesn't work so well with
>>> > an external monitor as it used to.
>>> >
>>> > What happens now when an external monitor is plugged in is that the
>>> > laptop screen runs at 1366x768 (as it should) but the external VGA
>>> > screen runs at 1024x768 and only shows the LH portion of the full
>>> > 1366x768 screen.
>>> >
>>> > It used to work fine on 10.04, when the external monitor was plugged in
>>> > the internal screen was disable and the external one ran at its native
>>> > resolution 1680 x 1050.  Now what happens is that the internal screen
>>> > contnues to run at 1366x768 and the external one runs at 1024x768 and
>>> > shows only the LH portion of the full screen.
>>> >
>>> >
>>> > Any ideas for a workaround/fix to get the external monitor right?
>>>
>>> What settings do you have in the Displays control panel?
>>>
>> Sorry, I'm running xubuntu so maybe shouldn't be asking here.
>>
>> However you have taken me some way to a solution as I can now *manually*
>> select the right resolution needed.  It used to 'just work' all by
>> itself though.
>>
>> Thanks.
>
> Ah.
>
> You didn't mention that, but then, I've found that if I mention that
> I'm using Mint 9 rather than Ubuntu 10.04, people generally won't
> answer me. If I don't mention this fact, I get Ubuntu-related answers
> that work fine. :¬/
>
> So I see why you didn't mention it, but still... Your response
> suggests that maybe you had not looked at the display settings at all,
> before you posted? Surely that cannot be the case?
>
> FWIW I found that under LXDE and XFCE, their display managers could
> not get me a working dual-head desktop on my Thinkpad X31, something
> GNOME and Unity did with ease.
>
> Sadly, the dual-head functionality was broken by 11.10 and 12.04 has
> not fixed it. Attempting to put it into dual-head mode results in a
> warning that the virtual resolution has been exceeded.

That may mean that your chipset cannot support 3D acceleration with
that size virtual desktop, for me that means I have to run unity 2d
rather than 3d when my external monitor is enabled.  Whether this has
any relevance to your setup I do not know.

Colin