Add support for action command prompts

[ulope]

Requested feature:

Octoprint has had support for Action Command Prompts for quite some time now.

It would be great if Mainsail also supported it.

Solves the following problem:

They are very useful for user interactive macros, e.g. filament loading / unloading, color change, confirmation prompts, etc.
See this very elaborate example (it says for Fluidd in the description, although I'm not sure if Fluidd supports this, Octoprint definitely does.)

Additional information:

The protocol is quite simple and described on the linked octoprint page.

[meteyou]

Octoprint is quite different to mainsail. Octoprint is server and webclient at the same time. Mainsail is only a webclient. So this is not possible without any change on the server side. Mainsail only supports Klipper macros to start this command.

[ulope]

Hm yeah alright that makes sense from an implementation standpoint, nonetheless I think this would be a great usability win in general.

Would you be open to implementing this / accepting a PR if server support (i.e. moonraker) were available?

[meteyou]

Ok... We spent the half evening discussing this feature internally with the crew, and I was probably a bit hasty in closing it. Maybe we have found a way to implement this. I will reopen this FR and test it before I can give feedback.

[ulope]

Awesome!
I also looked a bit more into this yesterday and it looks to me that the RESPOND messages are already coming through to the frontend via the notify_gcode_response websocket messages.

So it should "just" be a matter of parsing the // action: prompt_... messages.
(And yes I know that "just" is a dangerous word in software development ;))

[meteyou]

yeah, thats my idea. Klipper use this "commands" already for talking with octoprint. so i can use it the same way and "just" parse the console output for these commands.