Scatter GL with shiny

app.R

library(shiny)

ui <- fluidPage(
  htmlwidgets::getDependency("echarts4r"), # add dependencies
  tags$script(src="https://cdn.jsdelivr.net/npm/echarts-gl/dist/echarts-gl.min.js"), # add webgl
  htmltools::includeScript("scatter.js"),
  div(id="chart", style="height:90%; width:100%; min-height: 400px;")
)

server <- function(input, output, session) {
  lst <- apply(unname(cars), 1, as.list)
  session$sendCustomMessage("draw-chart", lst)
}

shinyApp(ui, server)

scatter.js

Shiny.addCustomMessageHandler('draw-chart', function(data){
  let dom = document.getElementById("chart");
  let myChart = echarts.init(dom);

  option = {
    title: {
	   text: data.length + ' Points'
    },
    toolbox: {
        left: 'center',
        feature: {
            dataZoom: { title:'zoom'}
        }
    },
    legend: { right: 10 },
    xAxis: [{    }],
    yAxis: [{    }],
    dataZoom: [{
        type: 'inside'
    }, {
        type: 'slider'
    }],
    animation: false,
    series: [{
        name: 'Data',
        type: 'scatterGL',
        data: data,
        symbolSize: 10,
        itemStyle: { opacity: 0.4 },
        large: true
    }]
  };

  if (option && typeof option === "object") {
    myChart.setOption(option, true);
  }

  $(window).on('resize', function(){
    if(myChart != null && myChart != undefined){
        myChart.resize();
    }
  });
})

One improvement would be to serialise the entire options from R giving you more flexibility to customise.