On 01/19/2016 12:59 AM, Simon McVittie wrote:
On 17/01/16 16:49, Ken Taylor wrote:
On 01/17/2016 10:05 AM, [email protected] wrote:
On Sunday, January 17, 2016 08:10:38 AM [Michal] wrote:
The usual pattern is that people ask about multiple screens but do not
really want them. Having multiple screens only limits what you can do
and gives you no meaningful benefits.
On some of the industrial (process control) systems I've been
responsible for,
we put up to 4 monitors (with different displays) driven by one
computer in
front of a single operator.
Multiple heads/outputs/monitors do not have to imply multiple X11
'screens'. They can, but they don't have to, and it's very rare to
prefer multiple screens.
'Screen' is a jargon term in this context, like 'display' - I'm putting
it in quotes to be unambiguous. If all your applications run with
DISPLAY=:0, or equivalently DISPLAY=:0.0, you have one X11 'screen',
potentially outputting to multiple monitors. If some of your
applications run with DISPLAY=:0.1 and are permanently tied to a
different set of monitors (probably a set of size 1), *that* is a second
X11 'screen'.
If you have multiple LCD/CRT/whatever monitors on one desk, or a laptop
and a monitor, or a laptop and a projector, the option that is usually
preferred is a single X11 'screen' spanning multiple monitors, with
optional runtime switching between mirroring (same content on each
output) and non-mirroring (different content on each output). That's
what Xrandr normally does on modern systems, and as far as I'm aware,
what all current desktop environments optimize for. It's also the X11
equivalent of all the supported arrangements in Windows and OS X.
For instance, on the laptop where I'm typing this (with Intel HD
graphics, as it happens), here's what my output looks like:
|----------|
| monitor ||--------|
| || laptop |
|----------||--------|
DISPLAY :0 --- screen :0.0 /-- HDMI2 --- monitor
\-- LVDS1 --- laptop
The equivalent with multiple 'screens':
DISPLAY :0 /-- screen :0.0 --- HDMI2 --- monitor
\-- screen :0.1 --- LVDS1 --- laptop
would mean I wouldn't be able to drag windows to and from the laptop, or
copy and paste between the two screens, and I don't have enough
historical X11 knowledge to know whether I'd need a second keyboard and
mouse for that setup.
I used to do this with gnome 2 using nvidia's --separate-x-screen
option, it didn't require a second keyboard and mouse. The reason I used
to do this is so that I could change virtual desktops / workspaces
independently per screen, ie screen 1 was on virtual desktop 3 and
screen 2 was on virtual desktop 4, I could then change screen 2 to be on
virtual desktop 1 without effecting screen 1. I found this more useful
then being able to drag windows between screens. Unfortunately modern
DE's often don't support this well as it involves running two instances
of the display manager at the same time. In my case I found that
enlightenment has this behavior without running separate x screens so I
use that instead now.
Cheers
Simon
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