What GPU?  Check Compiz/CCSM as Ted mentioned, looking under general at the resolution, gl modes, vsync, etc is often related to compositing window managers.  Multi-monitor always required manual tweaking to behave at all, if ever with compiz.

I'd blame Compiz, it tends to be a basketcase for me behaving like you'd mentioned, which is generally gpu/rendering problems.  Sometimes it's just bad at autodetecting its setup, most times it just doesn't play well with a gpu driver, vsync, gl features, etc.  I've found amd gpu's + unity just never work right, especially with propietary blob fglrx.

Best bet is if you ran without compiz enabled (metacity --replace &), it'd work fine.  I did this for years as compiz just could never deal with my 6x display config, especially with gl games.  KDE could with kwin, or I'd install cairo-desktop and disable compositing all together.

I'll second KDE (kubuntu-desktop) here, it was generally far more stable, and in most cases I think is fine.  Newer version of Plasma and KWin are very slick.

I did however have to stop using KDE recently as moving from 6x 1080p monitors to 3x 4k tv's presents a situation that seems to aggravate the driver, hardware, as well as the desktop apps down to Qt itself.  Being TV's, they're not smart about things like DPMS, and turning them off at night is like unplugging them to the pc.  This causes all sorts of weird behavior I'm finding, plasma4.x u14.04+fglrx)couldn't remember which monitor was which to put things back properly when returning, and plasma 5.x (u16.04+ati/mesa) regressed with QT so still cannot deal with displays coming and going well to not simply freak out at times.  Again, damn compositors.

I tried Ubuntu desktop moving off KDE again.  I really do try to give it a chance to work, only it simply never does, especially with very large/abnormal resolutions.  This time it would load the background, and just never give the panel overlays.  Compiz freaked out like yours at start in some ugly way, couldn't even get a terminal in the wm to probe around or unbreak compiz.  I'd had to drop to tty and restart lightdm to get out of it.  Sigh, next...

I'm using cinnamon now, less buggy, clutter compositing can handle it just fine even at 11520x2160, but monitors coming and going still occasionally cause one display to drop to 480x620 resolution, which plasma would do too, but deal much worse with it.  These might be due to my DP-to-HDMI2.0 adapters to get 4k@60hz, still tbd...  I do miss KDE features still with Cinnamon.

Every WM loves to composite desktops these days, yet none deal with large resolutions well when taxing a gpu, or just buggy driver.  I'd prefer compositing be optional always, or make it suck less.

-mb


On 06/18/2016 10:14 AM, Dennis McClellan wrote: