osc.lua: add idlescreen and osc-idlescreen

[Dudemanguy]

This is mainly for other user scripts that may conflict with the osc
logo in some way. While you can use script-message and
shared-script-properties (highly discouraged in the documentation for
some reason) to work around this, there's still some brittle edge cases
and complicated logic that can pop up. Adding an option for these two
things (the logo and the "drop files..." text) is really trivial and
would make things easier for scripts. Discussed in a couple of issues
below:
#10201
CogentRedTester/mpv-file-browser#55

[Dudemanguy]

I've changed it so only one option (idlelogo) controls all of this now. I also added a script-message that can be used to toggle this osc-idlelogo.

[stax76]

I tested it by changing mpv.net and the osm script accordingly, it works fine, thank you.

[stax76]

I think it would be helpful for scripts writing the osc-idlelogo state to shared-script-properties, much like osc-visibility is written to shared-script-properties. This would allow scripts to temporarily change the state and afterwards restore it. Restoring it, at least for me, is not important, but would still be nice if it could be done.

In my osm script, before I show my menu, I do this:

1. Save osd-level in variable
2. Set osd-level to 0
3. Send script-message osc-idlelogo no
4. Sleep 100 ms
5. Restore osd-level

https://github.com/stax76/mpv-scripts/blob/main/osm.lua#L101

[Dudemanguy]

I think it would be helpful for scripts writing the osc-idlelogo state to shared-script-properties, much like osc-visibility is written to shared-script-properties.

It now does this.

[sfan5]

Code lgtm but the commit message is missing a colon

[stax76]

It now does this.

Thanks, I'm looking forward to this getting merged.

[Dudemanguy]

I'm thinking about instead making the ASS text in here configurable so you could just pass an empty string (i.e. no logo). It would be more flexible. The implementation is a little trickier though because the logo is technically multiple strings not one so it would not be as simple as a typical string conf option.

[Dudemanguy]

I'm thinking about instead making the ASS text in here configurable

Decided to ax this idea. I renamed this to idlescreen and osc-idlescreen. Should be OK now. I'll double check it in a bit to make sure I didn't somehow goof up find/replace.