Visual presentations on the PI could get stuck for various reasons. It might be useful to detect and respond to that.
This tool takes snapshots of the current output displayed on the screen. It uses a configurable interval.
Each time a snapshot was taken it calculates a simple checksum and compares it to the previous checksum. If the checksum was unchanged (which probably means that the output on the screen hasn't changed) it will increment a "stuck" counter. If that counter passes a configurable threshold the program exists with exit status 0 and you can take actions.
Settings are provided using environment variables:
WATCHDOG_INTERVAL - seconds between taking snapshots
WATCHDOG_COUNT - number of times a checksum can be equal
to the previous value without triggering.
Build the tool by running make. Then start it:
WATCHDOG_INTERVAL=1 WATCHDOG_COUNT=3 ./visual-watchdog && echo "it's stuck"
The tool will only exit with error code 0 if it detects that the output didn't change.