SagUI

Waffle chart

A ten by ten unit chart where every cell is one percent, and cells fly to their new group when the data changes.

import { WaffleChart } from "@sagui/ui";
Markdown
Loading demo

When to use

  • Showing shares of one whole where people should be able to count units.
  • Comparing the same categories across a few datasets, such as countries or years.
  • Replacing a pie or donut when small shares need to stay visible.

When not to use

  • Use line-chart or streamgraph for how shares change over time.
  • Use bar-chart when exact comparison of many categories matters more than the whole.
  • Use sunburst for nested parts of a whole.

Installation

Install the package and import the styles once. The installation guide covers the Tailwind setup.

$ npm install @sagui/ui

Usage

example.tsx
import { WaffleChart } from "@sagui/ui";

const mix = [
  { key: "wind-solar", label: "Wind and solar", value: 218 },
  { key: "hydro", label: "Hydro", value: 20 },
  { key: "gas", label: "Gas", value: 76 },
  { key: "coal", label: "Coal", value: 132 },
  { key: "other", label: "Other", value: 61 },
];

export function PowerMix() {
  return <WaffleChart data={mix} label="Electricity generation, 2023" unit="TWh" />;
}

Examples

Changing the data

Each cell follows its category and flies to the new block when the data changes.

Loading demo

API reference

WaffleChart

A unit chart where every cell is one share of the whole. When the data changes, cells keep following their category and fly to their new block with a staggered spring, and the shares in the legend roll to their new values.

Prop Type Default Description
data (required) WaffleCategory[] – Categories in fill order: { key, label, value, color? }. The first fills from the bottom-left corner, column by column. Shares come from the total.
label (required) string – What the whole is, such as "Electricity generation, 2023". Names the chart, the summary, and the table.
unit string "" Unit after raw values in the tooltip and table, such as "TWh".
formatValue (value: number, category: WaffleCategory) => string – Formats raw values. Shares are always percentages.
rows number 10 Grid rows. rows × columns cells make the whole.
columns number 10 Grid columns. 10 × 10 means one cell per percent.
accentKey string | null first key The category painted in the first chart color (--color-chart-1). The next three take chart colors 2 to 4 and later ones fall back to neutral steps.
activeKey string | null – Controlled focused category. Other cells dim while one is focused.
defaultActiveKey string | null null Initial focused category when uncontrolled.
onActiveChange (key: string | null) => void – Called when a legend item is pinned or released.
legend boolean true Category list with rolling shares. It sits beside the grid from 420px and below it on narrower containers.
decimals number 0 Decimal places for shares.
emptyLabel string "No data" Message when the data is empty or sums to zero.
ref Ref<HTMLElement> – Forwarded to the figure.
className string – Extra class on the figure.

Keyboard interactions

Keys Action
Tab Focuses the grid, then each legend item.
Arrow keys Move the reading cell by cell across the grid.
PageUporPageDown Jump to the first cell of the previous or next category.
HomeorEnd Go to the first or last filled cell.
Escape Clears the reading.
EnterorSpace on a legend item Pins or releases that category.

Accessibility

  • The grid is a focusable group with a roledescription and instructions; cells are decorative and aria-hidden.
  • A polite live region reads the category, share, and value under the keyboard cursor.
  • A visually hidden summary and a table list every category with its value, share, and cell count.
  • Legend items are toggle buttons with aria-pressed; identity never relies on colour alone because every category is named in the legend.

Motion

  • Cells are persistent: a data change keeps as many cells in place as possible and flies the rest to their new block, staggered by position so the grid refills like a wave.
  • A travelling cell dips in scale mid-flight and changes colour with the same delay, so it reads as lifting out of one group and landing in another.
  • Shares in the legend roll to their new values on a critically damped spring.
  • The first time the chart is seen, cells pop in from the bottom-left corner.
  • Reduced motion places cells and shares immediately and drops the dip, pop, and stagger.

Responsive behavior

  • The grid is square and fills up to 300px; the legend moves beside it from 420px of container width.
  • Legend labels truncate with an ellipsis; the full name stays in the tooltip, the live region, and the table.
  • Touch reads cells with a press and drag; the page still scrolls vertically.

Performance

  • One element per cell, 100 by default, animated with transforms only.
  • Hover is resolved from pointer position arithmetic, not per-cell listeners.
  • Grid size is measured with one ResizeObserver.

Notes

  • Choose it for part-to-whole with four to eight categories where countable units help, such as energy mix, survey answers, or budget split.
  • Keep categories in a meaningful order; the fill order is the reading order.
  • Use accentKey for the category the story is about and leave the rest neutral.
  • Switching datasets with the same keys is where it shines: cells travel instead of repainting.

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