Kicad 11 support for bouni/kicad-jlcpcb-tools?

[z2amiller]

This change sounds pretty disruptive -- KiCad will no longer support the existing Python SWIG implementation
but instead will wrap some kind of IPC model. Honestly it sounds a lot better, but also might require quite a
bit of work to translate the plugin to the new architecture.

I'm willing to explore some of the work for this, but my only KiCad plugin experience is writing bugfixes
and selfish features that I want. :-) So I might not be terribly efficient with it.

It sounds like the new API is available starting in KiCad 9
so switching to the new API shouldn't leave too many users behind - it sounds like the existing policy is to
support $current-2 versions or so anyway. And I guess the old SWIG based version can always be left
on a branch for any critical bugfixes.

[z2amiller]

BTW I've been letting CoPilot drive an IPC implementation (with lots of guidance) of IPC support. Honestly CoPilot
was pretty good at this since a lot of it is just refactoring and mechanical translation.

My rough implementation plan was:

1. Encapsulate all of the current things that called the SWIG bindings into an abstract adapter/facade class.
2. Create the SWIG and Standalone implementations of the abstract class.
3. Switch all of the existing callers to use the adapter classes.
4. Create an IPC implementation of the abstract class.
5. Hack in all of the stuff to make KiCad recognize this as an IPC plugin instead.
6. ???
7. Profit

After some amount of guidance and token grinding, I at least have a prototype that works and generates JLC-able gerber files but it's rough around the edges. Some of that roughness is in KiCad itself, I think. Current rough edges:

• I think there's a bug in KiCad itself where it won't draw the tooltip icons to launch the plugins right away. I can't get it to render the icons until after I've visited the 'Settings -> PCB Editor -> Plugins' setting menu and toggled a box on and off to make it refresh the plugins. I don't think this is just something that I've done wrong, because when I dropped in one of the example plugins from the KiPy directory, that also has the same behavior. (I'm going to see if 10.0.1-rc1 also has this bug)
• It's generally slower. It's using RPCs over a socket to communicate rather than SWIGged C++ calls, so there's transmission and serialization overhead on both sides that just isn't there with SWIG. My prototype is noticeably slower to launch and slower to operate. Not unusably slow, but noticeable IMO.
• KiCad 10 doesn't support gerber plotting operations - it farms all of this out to kicad-cli. It works (I've uploaded the generated gerbers to JLC), but there's a workflow bug here that's certain to bite people. Because you pass the .kicad_pcb file to kicad-cli to generate the gerbers, you must save the board first in the editor because you pass that file to the CLI. It does look like you can force a .save() programmatically but that'll be a behavior change.
• The plugin installation itself is different, and I don't know how it will resolve a plugin being in both places or being installed both ways. I don't know if the project will want to have an entirely new package that is set up to install as an IPC-based package, or if there will be migration assistants to move things, or what.