[SOLVED] Openbox - setting different dpi on external monitor

Question

[SOLVED SUMMARY]
After the suggestion from Max, I've got two instances of openbox running on the different screens.
the xorg.conf I used for this is below.
then I used the following addition to ~/.xinitrc to start two instances and set the dpi of the laptop screen:
DISPLAY=:0.1
exec openbox &
DISPLAY=:0.0
exec xrandr --output eDP1 --dpi 192 &
exec openbox-session
[/SOLVED SUMMARY]
[ORIGINAL POST BELOW]
Hello,
I want to be able to set a different dpi for my laptop screen  (macbook pro retina 13 inch late 2013  11,1   integrated graphics (not nvidia))
and my external monitor, as the laptop screen has a pixel density more than double that of the external monitor
if I start openbox using:                           
startx
then text on the laptop is too small,  but everything on the monitor is ok. Conversely if I start openbox with
startx -- -dpi 144
then for the most part, things scale up nicely on the laptop, but everything on the monitor is too big.
So what I have tried to do is set the the dpi with xrandr:
xrandr --output eDP1 --auto --dpi 144 --output HDMI2 --auto --rotate right --dpi 96 --right-of eDP1
xrandr outputs a configuration that looks ok, but the display doesn't change:
Screen 0: minimum 320 x 200, current 3760 x 1920, maximum 32767 x 32767
eDP1 connected 2560x1600+0+0 (normal left inverted right x axis y axis) 286mm x 179mm
2560x1600 60.0*+
2048x1536 60.0
1920x1440 60.0
1856x1392 60.0
1792x1344 60.0
1600x1200 60.0
1400x1050 60.0
1280x1024 60.0
1280x960 60.0
1024x768 60.0
800x600 60.3 56.2
640x480 59.9
DP1 disconnected (normal left inverted right x axis y axis)
HDMI1 connected 1200x1920+2560+0 right (normal left inverted right x axis y axis) 495mm x 310mm
1920x1200 60.0*+
DP2 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
There seem to be a thousand ways to set up multiple screens, so it would be great to hear from anyone who has any suggestions about the best ways for me to approach this,
should I  set up seperate monitors in Xorg.conf,
or even seperate X DISPLAYs and launch multiple instances of openbox?
thanks
Mathew
[EDIT]
on re-examining, while the dimensions listed by xrandr seem about right, the xrandr command isn't changing them, they seem to be  defaults
Last edited by mathew (2014-02-26 09:37:46)

Answer 1

I created this xorg.conf
Section "ServerLayout"
Identifier "X.org Configured"
Screen 0 "Screen0"
Screen 1 "Screen1"
Screen "Screen1" RightOf "Screen0"
InputDevice "Mouse0" "CorePointer"
InputDevice "Keyboard0" "CoreKeyboard"
EndSection
Section "Files"
ModulePath "/usr/lib/xorg/modules"
FontPath "/usr/share/fonts/misc/"
FontPath "/usr/share/fonts/TTF/"
FontPath "/usr/share/fonts/OTF/"
FontPath "/usr/share/fonts/Type1/"
FontPath "/usr/share/fonts/100dpi/"
FontPath "/usr/share/fonts/75dpi/"
EndSection
Section "Module"
Load "glx"
EndSection
Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
EndSection
Section "InputDevice"
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/input/mice"
Option "ZAxisMapping" "4 5 6 7"
EndSection
Section "Monitor"
Identifier "Monitor0"
VendorName "Monitor Vendor"
ModelName "Monitor Model"
EndSection
Section "Monitor"
Identifier "Monitor1"
VendorName "Monitor Vendor"
ModelName "Monitor Model"
EndSection
Section "Device"
Identifier "Card0"
Driver "fbdev"
BusID "PCI:0:2:0"
Option "ZaphodHeads" "eDP1,DP1,HDMI1,DP2,HDMI2,VIRTUAL1"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Card0"
Monitor "Monitor0"
SubSection "Display"
Viewport 0 0
Depth 1
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 4
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 8
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 15
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 16
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen1"
Device "Card0"
Monitor "Monitor1"
SubSection "Display"
Viewport 0 0
Depth 1
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 4
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 8
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 15
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 16
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 24
EndSubSection
EndSection
If I put this in ./.xinitrc
DISPLAY=:0.0
exec openbox &
DISPLAY=:0.1
exec openbox
it fails, unfortunately there's not much of an explanation in the Xorg.log
This will launch:
DISPLAY=:0.0
exec openbox
but the screen will be mirrored at the resoultion of the smallest screen.
I'm guessing my xorg.conf is wrong, but I haven't been able to find any good information on setting up seperate X screens with intel integrated video