OK. That's a third point of proof that you're not running XMir. You have an interlaced mode "1920x1080i" which is not possible with Mir. So this can't be a Mir or XMir bug.
The X log files say it's "radeon" misdetecting the display size. So I'll reassign the bug to that... [ 21.327] (II) RADEON(0): clock: 27.0 MHz Image Size: 160 x 90 mm ** Also affects: xserver-xorg-video-ati (Ubuntu) Importance: Undecided Status: New ** Changed in: mir Status: Incomplete => Invalid ** Changed in: xmir Status: Incomplete => Invalid -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-ati in Ubuntu. https://bugs.launchpad.net/bugs/1383397 Title: Desktop PC detected as Phablet To manage notifications about this bug go to: https://bugs.launchpad.net/mir/+bug/1383397/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp