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killkrt

Member

From: Italy

Registered: 2016-02-24

Posts: 35

[?] Setting DPI and 10bpc correctly

Hi,

I have a GTX 970 Ti and a Dell P2715Q (4K monitor that supports 10bpc) and I am using Cinnamon as desktop environment, I would like to understand how to set correctly DPI and bit depth.
This is a snippet from my /etc/X11/xorg.conf:

Section "Monitor"                                                                                                                                                                         
      Identifier     "Monitor0"                                                                                                                                                             
      VendorName     "Dell"                                                                                                                                                                 
      ModelName      "P2715Q"                                                                                                                                                               
      HorizSync       28.0 - 33.0                                                                                                                                                           
      VertRefresh     43.0 - 72.0                                                                                                                                                           
      Option         "DPMS" "true"                                                                                                                                                          
      DisplaySize    596 335                                                                                                                                                                
      Option         "UseEdidDpi" "false"                                                                                                                                                   
 #    Option         "DPI" "144 x 144"                                                                                                                                                     
 EndSection

If I check which DPI has been computed (using: grep -i dpi /var/log/Xorg.0.log) I get this:

[  1103.477] (**) NVIDIA(0): Option "UseEdidDpi" "false"
[  1103.925] (**) NVIDIA(0): DPI set to (163, 163); computed from "DisplaySize" Monitor

So it would seem to be nice, but actually the DPI set is 96x96 as xdpyinfo reports:

screen #0:
  dimensions:    3840x2160 pixels (1016x572 millimeters)
  resolution:    96x96 dots per inch

So everything is too small to be seen without make my eyes bleeding!!!
It seems that my settings in xorg.conf are overwritten by someone else... Who? How I can find it and fix it?

Another strange thing is that if I set the bit depth to 30:

Section "Screen"                                                                                                                                                                          
      Identifier     "Screen0"                                                                                                                                                              
      Device         "Device0"                                                                                                                                                              
      Monitor        "Monitor0"                                                                                                                                                             
      DefaultDepth    30                                                                                                                                                                    
      SubSection     "Display"                                                                                                                                                              
          Depth       30                                                                                                                                                                    
      EndSubSection                                                                                                                                                                         
EndSection        

I am able to see only the menu bar in the bottom the screen, the rest of the screen is completely black, and it seems that the UI is stuck, I can see the mouse pointer floating around, but clicking and dragging is worthless, no reaction, no feedback. This is pretty strange!

Could you help me?

Thank you.

Last edited by killkrt (2016-05-11 21:45:28)

brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: [?] Setting DPI and 10bpc correctly

I can only sympathize - XFCE does the same daft thing, but at least there's an easy way to patch it back to sensible behaviour.