Draw Lines via command

[VanillaViking]

Hello, thanks for making and maintaining gromit-mpx.
This PR aims to implement the feature requested in #161

The original feature request also suggested opacity customization, however by the looks of it, opacity seems to be application-wide rather than individual lines? I was unsure how to implement it here. Would appreciate some guidance in that matter.

I would appreciate if you could review and provide some feedback on this code 😄

[bk138]

Thanks! I'll have a look ASAP!

And yes, opacity is per-screen, not per line; safe to leave this out.

[bk138]

Surprisingly small PR, good work so far! Only minor change requests.

[VanillaViking]

Thanks for the review!

I mainly use Xorg, but I briefly tested this out on wayland using Hyprland and it seems to work as expected.

As for the failsafe checks, it seems that atoi attempts to convert any given value to an int, or returns 0 if it can't. This would take care of most type issues, so I added checks to ensure that the coords fell within the screen area. Let me know if this is okay.

Maybe it's a good idea to include example usage of the command, in the README?

Everything else should be fixed 👍

[bk138]

Code-wise looks good to me, I also tested under Wayland and it draws lines, but only red ones. I'm probably missing out on the correct color format so I guess adding an example to the README is indeed a good idea. Thanks for the good work so far!

[bk138]

Thanks for the quick reply and the contribution!