Created attachment 114706 [details]
xorg log file
3.19.2-1-ARCH #1 SMP PREEMPT Wed Mar 18 16:21:02 CET 2015 x86_64 GNU/Linux
Basically on a vanilla configuration (I just got the laptop so no xorg.conf or anything in xinit) the driver fails to detect the resolution and (as a result I guess) it fails also to calculate the DPI and set's it to 96.
1) [ 818.122] (II) intel(0): Setting screen physical size to 508 x 285
It's wrong, my screen is a full HD 15.6" 345x194mm
2) [ 818.089] (==) intel(0): DPI set to (96, 96)
Which is confirmed by xdpyinfo:
xdpyinfo | grep -B2 resolution
dimensions: 1920x1080 pixels (508x285 millimeters)
resolution: 96x96 dots per inch
However xrandr shows eDP1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 345mm x 194mm
Maybe becuase was disabled and enabled during startx? I don't know.
This cause most of the DE's display everything in miniature and basically the laptop is unusable (otherwise you go blind).
Created attachment 114707 [details]
dmesg if needed
Created attachment 114708 [details]
xrandr verbose output
Created attachment 114709 [details]
The xrandr screen size comes from your EDID. The DPI is an artificial number to match X protocol expectations, and the display dimensions adjusted to match X. This is a long, long standing issue of which the answer has been "those which cannot handle DPI are told 96, those that do can query it in on a per-monitor basis via xrandr".
Sorry but is that supposed to be an answer?
It handles everything correctly under windows, why it shouldn't under Linux?
An one very imporant quesition wasn't answered the question why INTEL detects the screen as a 508 x 285mm while it's not. And forgive me if I'm wrong but it's Xorg who get's the config from Intel and not the opposite.
It detects it as 345mm x 194mm. Everything else is a lie X has chosen to maintain for over a decade.
[ 818.122] (II) intel(0): Setting screen physical size to 508 x 285
Is not set by Intel but by Xorg itself is that correct?
If that's so I should fill a bug against Xorg?
It's a policy imposed by X that the core protocol is 96dpi. To get the true dpi, clients are expected to RandR. See bug 23705, and a later thread at bug 41115.