How I built a scriptable Lua extension engine inside my C++ activity tracker (and almost lost my mind to deadlocks) (opens in new tab)

Hey! I've been building HPR, an open source activity tracker and window tracker written in C++23. It watches your active window, builds a history of where your time went, and runs locally with zero accounts and zero telemetry. Think of it as a lightweight ActivityWatch alternative with native Wayland support. At some point I decided it wasn't enough to just track windows. I wanted people to be able to extend it. So I built a Lua extension engine into it. Here's how that went. The basic idea E...