Bar-Bell API

Chain segments across each row to see exactly where every step's share of the total lands - props, events, and engine below; see it move on the Bar-Bell demo.

Import

Web Component

import "@michi-vz/wc/bar-bell-chart";
// <michi-vz-bar-bell-chart> is now defined

Vanilla JS

import { mountBarBellChart } from "@michi-vz/core";

const chart = mountBarBellChart(el, props);

Props

Prop	Type	Default	Description
timeline	boolean | TimelinePeriodConfig	-	Opt-in "play through years": snapshots one period at a time over the period tags in the data, with a headless controller (`chart.timeline()`) plus the built-in play button + scrubber. Values tween between periods unless `interpolate: false`. Off by default; wins over `progressiveDraw` when both are set.
progressiveDraw	boolean | ProgressiveDrawConfig	-	Opt-in reveal animation: wipes the marks in left to right on mount (a clip reveal; axes and titles stay put). `true` uses defaults (1200 ms, easeInOutCubic); a config tunes durationMs, easing, autoplay, and replayOnUpdate (`tipLabel` is LineChart-only and ignored here). Off by default; respects prefers-reduced-motion (renders fully drawn instantly) and `replay()` re-runs it.
dataSet*	BarBellDataRow[]	-	Array of rows (one per date/y-band); within each row the keys are laid out cumulatively along x as thin bars capped by end-cap circles
keys*	string[]	-	Ordered segment keys to draw per row; their values accumulate left-to-right and each gets a colored bar plus end-cap circle
title	string	-	Optional chart title rendered above the plot
xAxisFormat	(d: number | string) => string	-	Formats an x tick value into its display label
yAxisFormat	(d: number | string) => string	-	Formats a y tick value into its display label
yAxisDomain	[number, number]	-	Explicit [min, max] for the cumulative value (x) axis; overrides the auto domain of [0, max cumulative row total]
ticks	number	5	Approximate number of axis ticks to generate
tickHtmlWidth	number	80	Width in px reserved for each y-axis (date) tick's HTML (default 80)
xAxisPosition	"top" | "bottom"	"top"	Where the cumulative value axis renders its tick labels: "top" (default, legacy header look) or "bottom" (clears room under the title)
tooltipFormatter	(row: BarBellDataRow, key: string, value: number) => string	-	Returns custom tooltip HTML for a hovered datum (sanitized before it is inserted)
isLoading	boolean	-	Show the loading overlay and skip the no-data check (legacy michi-vz parity).
isNodata	boolean | ((dataSet: BarBellDataRow[] | null | undefined) => boolean)	-	No-data override: boolean, or a predicate on the data; default = empty data.
noDataLabel	string	-	Text for the vanilla default no-data overlay (ignored when suppressed).
suppressDefaultOverlay	boolean	-	A framework wrapper sets this to render its OWN loading/no-data node instead.
dodgeOverlappingCaps	boolean	-	Spread overlapping end-caps vertically, centred on the row line (default ON, legacy parity); pass false to keep them stacked.
onHighlightItem	(labels: string[]) => void	-	Called when the hovered/highlighted label(s) change

Common props - shared by every chart (14)

Prop	Type	Default	Description
width	number	900	Chart width in pixels
height	number	480	Chart height in pixels
margin	Margin	{ top: 50, right: 50, bottom: 50, left: 100 }	Inner margins (top/right/bottom/left, in px); default 8 (36 top with a title)
colors	string[]	-	Categorical palette for rings without an explicit colour or colorsMapping entry
colorsMapping	Record<string, string>	-	Explicit label -> colour map; takes precedence over the palette and per-item colours
highlightItems	string[]	-	Labels to emphasise (active styling); others keep their base opacity
disabledItems	string[]	-	Labels to hide entirely (ring + track removed; remaining rings keep their radii order)
renderer	"svg" | "canvas" | "webgpu"	"svg"	Render as inline SVG (default) or to a canvas / WebGPU layer; getContext() is identical either way
locale	string	-	BCP-47 locale used for number formatting
skipColorMappingDispatch	boolean	false	External-CSS mode: unmapped labels resolve to transparent and onColorMappingGenerated is not emitted, so arc colours come from your CSS via the data-label-safe contract
enableTransitions	boolean	true	Animate opacity/arc changes with CSS transitions (SVG renderer; default true)
onColorMappingGenerated	(mapping: Record<string, string>) => void	-	Called with the resolved label -> colour map after the chart assigns colours
onChartDataProcessed	(context: ChartContext) => void	-	Called with the renderer-agnostic ChartContext whenever the data is (re)processed
onDataWarning	(warnings: DataWarning[]) => void	-	Called with any non-fatal data warnings (out-of-range values, duplicate labels, ...)

Events

The web component dispatches these bubbling CustomEvents (the engine exposes the same via the on* callbacks in the table above):

Event	Detail	Fires when
michi-vz:highlight	string[]	hover highlight changes
michi-vz:colormapping	Record<string, string>	a color mapping is generated
michi-vz:dataprocessed	ChartContext	data is (re)processed
michi-vz:datawarning	DataWarning[]	input warnings are detected

getContext()

mountBarBellChart(el, props).getContext() returns a renderer-agnostic BarBellChartContext (structured stats + a deterministic natural-language summary + an a11y table). See LLM context.

Source

Props are typed as BarBellChartProps in @michi-vz/core.