Selected samples / points / categories
Scatter: selected point ids (ascending, visible series only); bars: category indices; candles: candle indices
Heatmaps / box plots / pies / combo / radar / gauge / funnel / waterfall charts have no brush: their 'select' payloads are always empty
Bars always brush x
Line / area: selected sample runs per visible series
Brushed x range in data units (sample index / x value / category index); null = cleared
Brushed y range ('xy' mode); null = whole y range or cleared
Brush selection (
'select'event payload,getSelection()).