Centerpiece should run as a singleton

[mweinelt]

When bound to a key, pressing the key multiple times should not stack multiple centerpiece instances above each other. That's just annoying when it happens and probably never intentional.

I checked rofi, and it does only ever have one instance, which makes it much nicer to use.

[friedow]

This would be a good improvement. I've ran into that problem myself a bunch of times.

What would be a good way to implement this? I've seen other applications writing text files with the current PID to the ~/.cache directory. Centerpiece would then check on startup if such a file exists, if so it would terminate the old instance and start the new one.

This would especially solve the edge case of old centerpiece instances being in places where you currently can't see them. e.g. a centerpiece instance being on a different workspace.

Any other implementation suggestions?

[a-kenji]

Usually locks will be held in /run, or /run/lock IIRC, but I am not 100% sure which solution is the most portable.