Using 12.10 on an older Toshiba, I can confirm this bug and lack of workaround. The only workaround I have discovered is to decrease the resolution of one or both displays by trial and error so that their total combined width does not exceed the graphics card's capabilities.
Though this is not actually a "bug" as far as I can tell, it is certainly an issue. Somewhere along the line the software has determined that the combined width of the monitors exceeds the graphics card's maximum horizontal rendering width for 3D-accellerated rendering. This hardware limitation should not be simply hidden by the software, which completely removes the unusable dropdown items; this is a terrible user feedback situation. At the _very least_, the software should indicate that, for whatever reason, normal rotation is not available in the current configuration. Normally, this is achieved by disabling the use of dropdown items, typically indicated by greying them out. What would be best, however, would be to use that big, ugly empty space below the "Mirror displays" checkbox to display a note to the user, combined with an explanatory tooltip on the disabled orientation and resolution dropdown items. For the note, something generic like:
> Note: Ubuntu has detected that your computer's hardware may not be able to support all possible display configurations.
For the tooltips on the disabled orientation AND resolution dropdowns, something like:
> This [resoluion|orientation] at the current [resoluion|orientation] exceeds your graphics card's 3D accellerated rendering capabilities and cannot be used.
> Tip: Try decreasing the resolution of one or both displays, or changing the displays' orientation.
A little more technical and precise, but still completely clear to any user that the current configuration can't be used for a known and acceptable reason, and provides a possible workaround.
This bug also exposes another issue, which is the current inability to arrange multiple displays to accurately represent their real-world orientation. Specifically, the inability to arrange displays vertically (which, considering that most displays are used such that they are wider than they are tall, would provide another potential workaround) is extremely frustrating. I can understand the problems having an OSX-style unified menubar imposes on vertical arrangement. That said, those issues are almost completely mitigated by the utilization of sticky edges. I propose that, in vertical arrangement, sticky edges be set to always-on for the top edge of a screen which is below another screen. This would allow boader and more accurate arrangement of screens, as well as providing a potential workaround for low-end hardware and multiple displays.
Finally, @Sebastien: muliple display configuration exceeding graphics hardware 3D accellerated rendering capabilities (low-end hardware with multiple displays; lots of diplays on mid- and high-end hardware) is not an unusual end-user configuration, and neither is it uncommon hardware. The lack of kernel support for old Toshiba lapop ACPI features is low-priority because the hardware it affects, like my ancient Toshiba Tecra A5-S516 laptop, is uncommon. This issue is certainly not low priority, though I would not go so far as to class it high priority. It is more of a medium, medium-low priority issue, whose SOLUTION is a simple bit of code to affect conditional user interface feedback. It's not like someone has to rewrite all of Ubuntu Unity to optimize for the ancient hardware, or even the absolute minimum possible amount of work required to support vertical display orientations. This is simple UI stuff to make your software more responsive and friendly; something you guys obviously want to do looking at your veritable cloning of all manner of OSX UI elements, paradigms, and phrasing. Beyond that, your comments here have been rude and dismissive. As Chrisopher said, "You clearly did not take the time to understand this bug and were rude to a user for no reason and sent someone away from the Ubuntu community." Shame on you indeed.
Using 12.10 on an older Toshiba, I can confirm this bug and lack of workaround. The only workaround I have discovered is to decrease the resolution of one or both displays by trial and error so that their total combined width does not exceed the graphics card's capabilities.
I fully agree with Christopher Reay's comment (https:/ /bugs.launchpad .net/ubuntu/ +source/ gnome-control- center/ +bug/983291/ comments/ 20), both on the technical reasons for this bug and his assessment of the behavior of Sebastien Bacher.
Though this is not actually a "bug" as far as I can tell, it is certainly an issue. Somewhere along the line the software has determined that the combined width of the monitors exceeds the graphics card's maximum horizontal rendering width for 3D-accellerated rendering. This hardware limitation should not be simply hidden by the software, which completely removes the unusable dropdown items; this is a terrible user feedback situation. At the _very least_, the software should indicate that, for whatever reason, normal rotation is not available in the current configuration. Normally, this is achieved by disabling the use of dropdown items, typically indicated by greying them out. What would be best, however, would be to use that big, ugly empty space below the "Mirror displays" checkbox to display a note to the user, combined with an explanatory tooltip on the disabled orientation and resolution dropdown items. For the note, something generic like:
> Note: Ubuntu has detected that your computer's hardware may not be able to support all possible display configurations.
For the tooltips on the disabled orientation AND resolution dropdowns, something like:
> This [resoluion| orientation] at the current [resoluion| orientation] exceeds your graphics card's 3D accellerated rendering capabilities and cannot be used.
> Tip: Try decreasing the resolution of one or both displays, or changing the displays' orientation.
A little more technical and precise, but still completely clear to any user that the current configuration can't be used for a known and acceptable reason, and provides a possible workaround.
This bug also exposes another issue, which is the current inability to arrange multiple displays to accurately represent their real-world orientation. Specifically, the inability to arrange displays vertically (which, considering that most displays are used such that they are wider than they are tall, would provide another potential workaround) is extremely frustrating. I can understand the problems having an OSX-style unified menubar imposes on vertical arrangement. That said, those issues are almost completely mitigated by the utilization of sticky edges. I propose that, in vertical arrangement, sticky edges be set to always-on for the top edge of a screen which is below another screen. This would allow boader and more accurate arrangement of screens, as well as providing a potential workaround for low-end hardware and multiple displays.
Finally, @Sebastien: muliple display configuration exceeding graphics hardware 3D accellerated rendering capabilities (low-end hardware with multiple displays; lots of diplays on mid- and high-end hardware) is not an unusual end-user configuration, and neither is it uncommon hardware. The lack of kernel support for old Toshiba lapop ACPI features is low-priority because the hardware it affects, like my ancient Toshiba Tecra A5-S516 laptop, is uncommon. This issue is certainly not low priority, though I would not go so far as to class it high priority. It is more of a medium, medium-low priority issue, whose SOLUTION is a simple bit of code to affect conditional user interface feedback. It's not like someone has to rewrite all of Ubuntu Unity to optimize for the ancient hardware, or even the absolute minimum possible amount of work required to support vertical display orientations. This is simple UI stuff to make your software more responsive and friendly; something you guys obviously want to do looking at your veritable cloning of all manner of OSX UI elements, paradigms, and phrasing. Beyond that, your comments here have been rude and dismissive. As Chrisopher said, "You clearly did not take the time to understand this bug and were rude to a user for no reason and sent someone away from the Ubuntu community." Shame on you indeed.