I built a greeter for greetd that got accepted as a known greeter (ndlm).
In short https://sr.ht/~kennylevinsen/greetd/ is a login manager daemon that uses greeters for logging into linux. It provides an SDK for programmers to create their own login solutions. The interface that takes in a username, password and a session can be anything. As per the repo README: “If you can run it from your shell in a TTY, greetd can start it. If it can be taught to speak a simple JSON-based IPC protocol, then it can be a greeter.”
My greeter https://github.com/ivandimitrov8080/ndlm was created because I got tired of seeing the classic linux flickering every time I booted into= linux. The flickering happens, because the available graphical greeters start eith= er an X or a wayland session to display graphics, which is a heavy operation to start resulting in a blank screen. That’s overkill for a simple program that has 3 inputs so I made mine not use any graphical environment while still providing graphics using Direct Rendering Manager. Rust’s cairo bindings help abstract away the logic behind generating the frames (image buffers that get sent to DRM). Pango and the pangocairo library provide font support. I wrote a custom plymouth (it’s the graphical screen when booting) theme parser so that the greeter can reuse the same colors from the boot screen.
The result is a boot process that does not display any flickering and looks uniform across the bootloader, plymouth and the greeter as the 3 processes use the same theme colors.
I guess next steps is to figure out how to make starting wayland not display the black flicker screen, but that’s out of scope for the ndlm greeter.