[solved] screen dimensions & xorg config

Question

I've been trying (finally) to improve the appearance of fonts in my system. In the process of following the wiki font configuration guide, I checked out the dpi/screen dimensions identified by xorg. According to my calculations, xorg is getting the physical dimensions of my laptop's display wrong. It correctly identifies the native resolution as 1366x768 and then uses a dpi of 96 to calculate physical dimensions:
$ xdpyinfo | grep -B2 reso
screen #0:
dimensions: 1366x768 pixels (361x203 millimeters)
resolution: 96x96 dots per inch
However, my laptop screen is 11.6" which I think is about 256.8x144.4 mm with a dpi of 136x135. Er... ish.
Trying to follow the wiki instructions for configuring xorg at https://wiki.archlinux.org/index.php/Xo … ze_and_DPI, I created a /etc/X11/xorg.conf.d/20-monitors.conf:
Section "Monitor"
Identifier "LVDS1"
DisplaySize 256.8 144.4 # In millimeters
EndSection
However, this produces pretty ugly results. Fonts look all wrong - at least in some applications - and things just generally seem too big. So I removed the config file and rebooted and everything looks OK again (actually a bit better than before - probably because I'd got through part of the font config guide). I have no non-default config files under /etc/X11/xorg.conf.d/ - just default files for evdev, quirks and synaptics.
So now I'm confused about what dimensions I should be using.
I would have thought that with the autogenerated settings above, I should find things not fitting onto the screen because X believes that the physical screen is larger than it really is. But that's not what happens. Everything fits fine. Plus I'm not sure how to check but the resolution looks comparable to the resolution I get in the ttys.
I'm using the intel i915 driver with various power-saving options (which don't affect display so far as I can tell). It's one of the integrated graphics chips. There's no separate graphics card to complicate (or improve!) things.
Could somebody explain what might be going on? Or give me a reference? I don't understand how the physical dimensions X uses can be incorrect and yet everything fit and look better than when I force it to use accurate ones.
Last edited by cfr (2012-03-06 18:31:35)

Answer 1

High resolution in the TTY means that you have KMS activated, which is a good thing.
Of course anything bigger than 96x96 or 100x100 DPI is going to look awkward, it's an 11.6 inch screen! Or did you actually try to bring a ruler to the screen and measure a 136x136 pixel image? There's this little thing called dot (pixel) pitch: 0.39, 0.33, 0.28, 0.265 mm, etc.
http://en.wikipedia.org/wiki/Dots_per_i … _standards
Obviously Microsoft's sneaky little hack had very long-term consequences, when instead they should've just used a better rendering method. "However, larger graphical elements meant less screen space on which to draw" - which is what you experienced when everything looked like it was on steroids.
Another very interesting article: http://www.tested.com/news/why-pixel-de … ution/371/