Screen doesn’t always shut off on its own

I had the same problem (also using yocto fido). I couldn't use the proposed answer because i didn't manage to build xscreensaver (has way to many dependencies)

I finally solved it by using xssstart and modifying slock which is a screen locker. I called it clicklock

https://github.com/zpfvo/clicklock

I also made a fork of xssstart with autotools build files for easy cross-compilation (just use inherit autotools in the recipe): https://github.com/zpfvo/xssstart

xssstart runs a command as soon as the screensaver gets enabled and clicklock is just a black fullscreen window which closes after the first touch or key event.

So you have to run xssstart clicklock

Finally figured out the problem - it was a DPI thing.

With no radeon or fglrx driver, the default DPI was 102x102, with either driver loaded it was setting the DPI to 96x96. When I tried using xrandr to set the DPI back to 102x102, it wasn't fixing the fonts because fonts in programs that were already running were not affected by the change.

Finally tried launching X by hand after editing my startx script to include "-dpi 102" in "defaultserverflags" and X then did start at 102x102 DPI, and text looked fine.

I still don't understand why the difference between 96x96 DPI and 102x102 DPI would make black letters develop gray patches, but at least I know how to fix it now!

Edit: To add some more details for anyone who Googles across this later with a similar issue:

1. Editing startx is a troubleshooting measure that doesn't make a permanent change (unless you normally start X from the command line). To permanently change it, I had to edit /etc/lightdm/lightdm.conf and set xserver-command=X -dpi 102 . This may differ depending on what login manager you use (gdm, kdm, etc.) but they should all have an option somewhere for what commands to pass to X when starting it, and that is where you want to change your DPI. You cannot change your DPI in xorg.conf or xorg.conf.d, as discussed here and here.

2. There is another setting, Xft.dpi, that tells the Xft what DPI to use for fonts. If this is not set anywhere, it should default to the same DPI X is using (I think). If it is set, you should be able to see what it is set to using "xrdb -q". It sounds like this setting can be changed in ~/.Xresources, ~/.fonts.conf, or your system-wide fonts.conf (distro-dependent location). I did not end up having to mess with this to get mine working, but wanted to include this in case it helps someone who Googles across this later.

3. 102x102 happened to be the correct DPI for my screen, but that doesn't necessarily mean it will be for yours. Consult the documentation for your monitor or try some different values to see what works for you.

4. It is also worth mentioning that the font configuration article at the Arch Linux Wiki is incredibly detailed and useful for a variety of font-related issues, regardless of what distro you actually use.