Does Vega support signals in Gradient stop offset property - dynamic

Question

I have a situation, where a Gradient Stop objects offset value, like this...
{"offset": 0.3, "color": "hsl(140,100%,42%)"},
Needs to be set dynamically. I have tried setting the offset to be { "signal": "0.3" }, like this...
{"offset": {"signal": "0.3"}, "color": "hsl(140,100%,42%)"},
and Vega seems to be interpretting this value as undefined/falsy i.e. as ZERO.
Am I stuck, or is there a way to update this value whilst the chart data changes?
Why do I need to do this? Well, we have data which has GOOD/OK/BAD thresholds, and because of this, we need to color our line charts line to indicate WHERE these thresholds lie. We are using a Gradient to color the line to match these thresholds. We have many data, so these thresholds are not fixed, so we need to update the Gradient, based on the LIVE data. Sadly, it appears Vega is not doing this.
I have tested this in full fat Vega, but no joy. Any help appreciated.

Answer 1

According to jheer, "Gradient definitions do not support the use of signals inside of them when provided as a value in an encoding. However, you can define gradients separately as signal values, which in turn can reference other signals."
Here is an example I mocked up.
{
"$schema": "https://vega.github.io/schema/vega/v5.json",
"width": 200,
"height": 200,
"padding": 5,
"signals": [
{
"name": "test",
"update": "{gradient: 'radial', stops: [{offset: 0, color: 'white'}, {offset: 0.2, color: 'blue'}, {offset: 1, color: 'white'}]}"
}
],
"marks": [
{
"type": "rect",
"encode": {
"enter": {
"x": {"value": 0},
"x2": {"value": 100},
"y": {"value": 0},
"y2": {"value": 400},
"fill": {"signal": "test"}
}
}
}
]
}