How to highlight the zoomed in bar and know the details of that bar in vega-lite? - vega-lite

Question

I am able to create the overview details bar graph and zoomed-in nicely when I select the range in the bottom graph. But I am having difficulty to highlight the bars in the zoomed-in graph and also know what bars have been selected.
{
"$schema": "https://vega.github.io/schema/vega-lite/v4.json",
"actions": false,
"data": {
"values": [
{ "created": 1595053277243 },
{ "created": 1595053277244 },
{ "created": 1595055277243 },
{ "created": 1594880606860 },
{ "created": 1594880604261 }
]
},
"vconcat": [{
"width": 1500,
"height": 300,
"selection": {
"highlight": {"type": "single", "empty": "none", "on": "mouseover"},
"select": {"type": "multi"}
},
"mark": {
"type": "bar",
"fill": "#4C78A8",
"stroke": "black",
"cursor": "pointer"
},
"encoding": {
"x": {
"field": "created",
"type": "temporal",
"scale": {"domain": {"selection": "brush"}},
"axis": {"title": ""},
"timeUnit": "utcyearmonthdatehoursminutes",
"update": {
"fillOpacity": {
"condition": {"selection": "select", "value": 1},
"value": 0.3
},
"strokeWidth": {
"condition": [
{
"test": {
"and": [
{"selection": "select"},
"length(data(\"select_store\"))"
]
},
"value": 2
},
{"selection": "highlight", "value": 1}
],
"value": 0
}
}
},
"y": {
"field": "created",
"type": "quantitative",
"aggregate": "count"
}
},
"config": {
"scale": {
"bandPaddingInner": 0.2
}
}
}, {
"width": 1500,
"height": 100,
"padding": 10,
"mark": "bar",
"selection": {
"brush": {"type": "interval", "encodings": ["x"]}
},
"encoding": {
"x": {
"field": "created",
"type": "temporal",
"timeUnit": "utcyearmonthdatehours"
},
"y": {
"field": "created",
"type": "quantitative",
"aggregate": "count"
}
}
}]
}
I tried to put the fill-opacity and stroke-width in encoding but doesn't seem to work. I also tried to patch the compiled vega in vega-embed to listen to the bar click event but it doesn't listen to the top (zoomed in) graph.
Example of what I am trying to do

Answer 1

Vega-Lite encodings have no update property. You can specify the features directly in the encoding mapping:
"encoding": {
"x": {
"field": "created",
"type": "temporal",
"scale": {"domain": {"selection": "brush"}},
"axis": {"title": ""},
"timeUnit": "utcyearmonthdatehoursminutes"
},
"fillOpacity": {
"condition": {"selection": "select", "value": 1},
"value": 0.3
},
"strokeWidth": {
"condition": [
{
"test": {
"and": [
{"selection": "select"},
"length(data(\"select_store\"))"
]
},
"value": 2
},
{"selection": "highlight", "value": 1}
],
"value": 0
},
"y": {"field": "created", "type": "quantitative", "aggregate": "count"}
}
Open the Chart in the Vega Editor