setting primary in multihead xorg.conf causes disregard of DisplaySize

Christopher Barry christopher.barry at
Wed Feb 10 15:09:29 CET 2016

On Wed, 10 Feb 2016 02:05:03 -0500
Felix Miata <mrmazda at> wrote:

>Sent too soon, and probably to the wrong place. I tried equivlent
>xorg.conf files with Nvidia G84 and nouveau, and with ATI Cedar and
>radeon. Neither have any such shortcoming, so I have to suspect this
>should have gone to intel-gfx as a driver bug. Anyone here agree, or
>know a config solution?
>Felix Miata composed on 2016-02-09 23:33 (UTC-0500):
>> Using the following, I get the display positions the way I want
>> them, but the DPI I want is disregarded. If I comment the primary
>> option line, DPI is obeyed, but the wrong display is primary. Am I
>> doing something wrong, missing something, is a ServerLayout section
>> required, or is there a bug here?  
>> # 50-device.conf
>> Section "Device"
>> 	Identifier	"IGMA"
>> 	Driver	"intel"
>> 	Option	"monitor-VGA1"	"analog"	# Intel
>> analog Option	"monitor-HDMI1"	"digital"	# Intel
>> HDMI aka DVI #
>> Option	"monitor-DP1"	"apple"		# Intel
>> DisplayPort EndSection  
>> # 50-monitor1.conf
>> Section "Monitor"
>> 	Identifier	"analog"
>> 	Option		"Primary"	"true"
>> 	Option		"PreferredMode"	"1680x1050"
>> 	DisplaySize	761 228 # 120 DPI @ 3600x1080
>> EndSection  
>> # 50-monitor2.conf
>> Section "Monitor"
>> 	Identifier	"digital"
>> 	Option		"PreferredMode"	"1920x1080"
>> 	Option		"RightOf"	"analog"
>> EndSection  
>> # 50-screen1.conf
>> Section "Screen"
>> 	Identifier	"ScreenLeft"
>> 	Device		"IGMA"
>> 	Monitor		"analog"
>> EndSection  
>> # 50-screen2.conf
>> Section "Screen"
>> 	Identifier	"ScreenRight"
>> 	Device		"IGMA"
>> 	Monitor		"digital"
>> EndSection  
>> TIA  

if kms is an option, I'm using xrandr to accomplish essentially this
for a triple-head setup in this script I use from lightdm.conf as:


where the script looks like (single line):
xrandr --output DisplayPort-0 --mode 1920x1200 --pos 1920x0 --rotate
normal --output DVI-1 --mode 1920x1200 --pos 0x0 --rotate normal
--output DVI-0 --mode 1920x1200 --pos 3840x0 --rotate normal --output
HDMI-0 --off

Not sure if that's helpful for you or not.

Christopher Barry

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