Extend non-HiDPI external display above HiDPI internal display

extend.sh

#!/bin/sh
# extend non-HiDPI external display on DP* above HiDPI internal display eDP*
# see also https://wiki.archlinux.org/index.php/HiDPI
# you may run into https://bugs.freedesktop.org/show_bug.cgi?id=39949
#                  https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/883319

EXT=`xrandr --current | sed 's/^\(.*\) connected.*$/\1/p;d' | grep -v ^eDP | head -n 1`
INT=`xrandr --current | sed 's/^\(.*\) connected.*$/\1/p;d' | grep -v ^DP | head -n 1`

ext_w=`xrandr | sed 's/^'"${EXT}"' [^0-9]* \([0-9]\+\)x.*$/\1/p;d'`
ext_h=`xrandr | sed 's/^'"${EXT}"' [^0-9]* [0-9]\+x\([0-9]\+\).*$/\1/p;d'`
int_w=`xrandr | sed 's/^'"${INT}"' [^0-9]* \([0-9]\+\)x.*$/\1/p;d'`
off_w=`echo $(( ($int_w-$ext_w)/2 )) | sed 's/^-//'`

xrandr --output "${INT}" --auto --pos ${off_w}x${ext_h} --scale 1x1  --output "${EXT}" --auto --scale 2x2 --pos 0x0

@JherezTaylor add ``--right-of eDP1to the end of finalxrandr`

Hello,
I came here by the ArchWiki article "HiDPI". Maybe you can help me...I came here to ask because I am not sure to which forum I should go. If I get a hint I will post at another place....

Your script isn't really working for me now but this (from the wiki) works for me:
xrandr --output eDP-1 --auto --output HDMI-1 --auto --panning 3840x2160+3840+0 --scale 2x2 --right-of eDP-1
BUT my hardware setup would need a --left-of. But with by replacing right with left I get a non-good result. I am not sure if it is a panning thing. Still not sire how this works. I think --left-of doesn't make a big difference.

EDIT: Specify "non-good": HiDPI screen fine all the time. LowDPI(FullHD) screen is broken. It is like the screen 4k in the "background". When I go over to the screen around the mouse it is like a zoom rectangle of the size 1920x1080 on the 4k "bachground"....This is difficult to discribe or so screenshot.... :(

I also get a "bad" result on my Asus 1920x1080 device. . . I also require a "left of" configuration. . . looking at these sed scripts. . . I wonder if there is a cleaner method. . .

Same thing is happening to me as for @a123qwertz567. Did you guys figure something out?

This works well for my current set up where I have a 4K laptop (XPS 9560) beneath a FHD external display, but I have to run it twice: first time the external monitor has a big chunk of whatever's on the 4K monitor, and the second time it goes in fine.

On Unity, connect first the external monitor, and on display config make sure the scale factor for both screens is 2. Then run the script, perhaps twice.

The downside of this approach is however the FHD monitor is a scaled down version of 4K, so your computer is in fact driving 2x4K monitors (plus the overhead of resampling) and this is very resource intensive. The image quality on the FHD monitor is not great.

I see the same as above with gnome 3. Unfortunately sometimes it doesn't seem to actually work on the second run

Thanks for this script! I typically have to run it twice, as well, but I'll take that over the alternative!

It's wierd. I seem to have a similar setup as many, a Surface Pro with a res of 2736x1824 and an external display in FHD, yet, if I run it as it is, the external display windows look very small. I want its scale to be 1 and the internal display to look better to the eye (i.e. scale of 0.5), this seems to do the opposite?

If I try to set the correct scaling, it looks weird, I guess I am not getting the formula, maybe I have to multiply by 2 rather than divide in the offset calculation?

Thanks a lot for this script! To have the full external screen area usable, I had to add theses bits :

Get internal screen height,

int_h=`xrandr | sed 's/^'"${INT}"' [^0-9]* [0-9]\+x\([0-9]\+\).*$/\1/p;d'` 

Calculate total width calculation,

tot_w=$(( $ext_w+$int_w ))

And at last, append this option to the final xrandr command.

xrandr [...] --fb ${tot_w}x${int_h}

I have an easy to modify python script here with arguably more options: https://github.com/ashwinvis/xrandr-extend