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by chadgpt3 3 days ago
X screens are legacy. It used to be you could connect to a particular screen by number to open windows on that screen but the modern way to do it is to have one big virtual screen. X screens were like having a separate X server for each monitor, but with a single shared cursor and shared VRAM. You can see why that's an obsolete model.
2 comments
rixed 2 days ago
Please do not see any malice in this naive question, but why is that an obsolete model? Back in the days I had very different displays that I could use to display various windows of a flight simulator (some dedicated to some instruments, the big one for the front view, for instance) and it was quite nice. It sounds like that would not be easy to replicate with a single shared frame buffer, but maybe I'm wrong (I've been using nothing but a small laptop screen for decades)
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chadgpt3 2 days ago
It's much easier to place a window at a specific position on a large frame buffer than to drag a window between screens when they are separate display servers.
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simmonmt 3 days ago
Yep. When did virtual screens come in? My last full time experience with X was with Xsun in the early 2000s under Solaris. There was a shared cursor, I thought you could drag windows between monitors, but I also thought the DISPLAY variable was different for each (though I could be misremembering)
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Liskni_si 3 days ago
2007 is when xrandr 1.2 came and made it feasible to use on a laptop - enable/disable outputs dynamically without restarting X.

Xinerama (the extension that enables one virtual screen over multiple outputs) existed before but the layout could only be defined statically - so you'd need to restart your X server with a different config if you wanted to connect a monitor or a projector or something.

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rwmj 3 days ago
$DISPLAY is definitely different for each X11 screen, ie. :0.0 for the first screen, :0.1 for the second and so on. (:1, :2 is used for more instances of the X11 server).

I can't recall any application able to use multiple X11 screens (except in the trivial sense that you could set DISPLAY when starting the application), and I've been using X11 since X11R4.

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