RFE: Don't make UI for freq/gain/gate in poly mode

[DBraun]

When I'm prototyping a polyphonic instrument in the IDE, I'm usually using the computer keyboard as MIDI input. This means I don't need the freq, gain, or gate parameters to show up in the GUI. Could there be a toggle (defaulting to off) that would prevent these parameters from being shown in the UI? I have also toyed with the idea of metadata like freq = hslider("freq [hide]", 440, 20, 20000, 1);, but maybe that's not a good idea.

[DBraun]

Any soundfile shows up as just a box with no interactivity, so I'd like to hide that too.

[sletz]

We have a hidden:0|1 metadata that could be used for that. I mean it it defined (It was actually added for use-cases like "instruments on smartphones", the so-called SmartFaust project, but not used for now in IDE).

[sletz]

And for the soundfile, hidden could be always done, but this would have to be done in https://github.com/Fr0stbyteR/faust-ui package.