i'm working in a simple project on my raspberry pi, which flash some leds in differ ways on some system events (like disk reading, ethernet communications, processor overload), and these leds need to be shut off some time after system is idle (these leds will behave varying their intensity when no sys activity detected).
To achieve idle detection, i'm using XScreenSaver, until here, everything works flawlessly.
As my project needed to be executed as daemon (etc/init.d) and needed to run with root privileges (because the pigpio library) the communication with X Server (via XOpenDisplay) is returning NULL every time, even when system is ready and in graphical interface. On terminal, running this manually, everything works perfectly.
as my research goes, i've understood that isn't possible to access X Server when there is no console available at boot time, and there is no way to access it for security reasons.
so i ask, how i could achieve this (detect idle time) on a simplest way possible? ( i tried self restart, tried setting DISPLAY variable on start script nothing seems to work.) I'm new on linux development and can't figure how to properly solve this.
Just awnsering my own question, if anyone having the same issue as me.
Detecting System Inactivity (Idle) outside X graphical interface, is just a matter of USB Keyboard / mouse activity by monitoring their IRQs (usually IRQ 1 /IRQ 12) on /proc/interrupt or more easy (supporting other USB Input like even Joysticks!) by monitoring /proc/stat on "softirq" line, second numeric column that contains numeric amount of bytes transferred when these devices has some / any input (mouse moving or key pressed / released)
This achieved easily in C by time to time, fopen / fread on these fields comparing the values with old ones.
Thanks a lot to my intensive researchs on Linux internals & User Olaf that have a huge knowledge on discover the obvious.