[...] this particular script makes use of several timeouts on button hover and click (to retrieve user's data from ListenBrainz). And there were multiple reports about the component failing with that, so that must be the problem.

With JSplitter in 64bit f2k of the same version the 'Configure panel...' item is not available in layout editing mode.

On Saturday I first tried JScript Panel 3 since I have it already in use for lastfm bio but I was unsuccessful with the script regor prepared for me with reference to SMP and JSplitter. The same script in JSplit Panel 3:

I will stick on JSplitter now since its newer JavaScript version is more compatible with examples I found on web.

I just tried upgrading to v3.6.1.14 from 3.6.1.10, and two out of three of my panels have stopped appearing with anything in them; they are just black.

const myData = [];

function calcData() {
     myData.length = 0;
     myData.push('this is data')
     .... // data code
}

function on_item_focus_change() {
     if (window.IsVisible) {
          calcData();
     } else {
          myData.length = 0;
     }
}

function on_paint() {
     if (!myData.length) {calcData()}
     .... // Paint code
}

Can it be done? Obviously, yes. As long as the files are analyzed first.

Has it been done?
There is at least one spectral script sample (I think it uses SOX) and my waveform script which may be used to display RMS levels, RMS peaks, or peak levels either as waveform or simple VU meter.

Anyway I don't see any point on doing anything more than that, since there are C++ components suitable for that. (and for sure I have zero interest on implementing your ideas)

Web View component would also be a great host for further experiments.

Meaning that these visualizations (e.g. spectrum analyzer using short chunk of full data pulled from ffprobe within milliseconds length) aren't affected by DSPs and it wouldn't work on internet radio

But don't writing new foobar2000 visualization components (which BTW is probably written in C++) is harder to make than WebAudio API visualizations that either use AudioWorklet or doesn't use AnalyserNode's built-in FFT at all (as either two can be easily ported to ones that doesn't use Web Audio API but still has an API to pull raw PCM data from currently-playing audio)?

A panel may be processing on background, but not painting. I differentiate both because some particular scripts delay processing during painting (seekbars for ex.).

Yes, that's a limitation with that approach. But some people (me for ex.) could not care less about radio or DSPs, since I want the original data of my tracks (and radio data has zero interest).

Neither I agree, nor disagree. Just saying there are so many options right now that it made no sense -for me- to code what has been already coded elsewhere. C++ should also offer better performance.

Anyway I would also appreciate audio data being available on this component, for sure.