chart-implementation

name	chart-implementation
description	Create interactive charts for car registration and COE data visualization using Recharts. Use when adding new chart types, fixing chart bugs, or implementing data visualizations.
allowed-tools	Read, Edit, Write, Grep, Glob

Chart Implementation Skill

Uses Recharts via shadcn/ui ChartContainer for data visualization. Always use CSS variables for colors (see design-language-system skill).

Core Pattern

All charts use ChartContainer from @sgcarstrends/ui/components/chart wrapped in ChartWidget from @web/components/charts/widget. Never use raw ResponsiveContainer directly.

"use client";

import {
  ChartContainer,
  ChartTooltip,
  ChartTooltipContent,
} from "@sgcarstrends/ui/components/chart";
import { ChartWidget } from "@web/components/charts/widget";
import { BarChart, Bar, CartesianGrid, XAxis, YAxis } from "recharts";

export function TopMakesChart({ data }: { data: { make: string; count: number }[] }) {
  const chartConfig = {
    count: { label: "Count", color: "var(--chart-1)" },
  };

  return (
    <ChartWidget title="Top Makes" isEmpty={data.length === 0}>
      <ChartContainer config={chartConfig} className="h-[300px] w-full">
        <BarChart data={data}>
          <CartesianGrid vertical={false} strokeDasharray="3 3" className="stroke-default-200" />
          <XAxis dataKey="make" tickLine={false} axisLine={false} className="text-xs" />
          <YAxis tickLine={false} axisLine={false} className="text-xs" />
          <ChartTooltip content={<ChartTooltipContent />} />
          <Bar dataKey="count" fill="var(--chart-1)" radius={[8, 8, 0, 0]} />
        </BarChart>
      </ChartContainer>
    </ChartWidget>
  );
}

ChartContainer

ChartContainer wraps Recharts' ResponsiveContainer with theming support. Set dimensions via CSS class on the container:

// ✅ Correct - height via className
<ChartContainer config={chartConfig} className="h-[300px] w-full">
  <BarChart data={data}>...</BarChart>
</ChartContainer>

// ❌ Wrong - raw ResponsiveContainer
<ResponsiveContainer width="100%" height={400}>
  <BarChart data={data}>...</BarChart>
</ResponsiveContainer>

Width/Height -1 Warning

Recharts ResponsiveContainer logs width(-1) and height(-1) warnings on first render before ResizeObserver fires. Fix by setting initialDimension on ResponsiveContainer in packages/ui/src/components/chart.tsx:

<RechartsPrimitive.ResponsiveContainer initialDimension={{ width: 0, height: 400 }}>
  {children}
</RechartsPrimitive.ResponsiveContainer>

Reference: shadcn/ui PR #8486, recharts #6716

ChartWidget

Wraps charts in a Card with title, subtitle, empty state, and entrance animation:

<ChartWidget
  title="Registration Trends"
  subtitle="Monthly breakdown"
  isEmpty={data.length === 0}
  emptyMessage="No trend data available"
>
  <ChartContainer ...>...</ChartContainer>
</ChartWidget>

Chart Config

Define chart config for theming and legend/tooltip labels:

const chartConfig = {
  diesel: { label: "Diesel", color: "var(--chart-1)" },
  petrol: { label: "Petrol", color: "var(--chart-2)" },
  electric: { label: "Electric", color: "var(--chart-3)" },
};

Performance

Memoize Data and Config

const chartConfig = useMemo(() => {
  return Object.fromEntries(
    categories.map((category, index) => [
      category,
      { label: category, color: `var(--chart-${index + 1})` },
    ]),
  );
}, [categories]);

Best Practices

1. ChartContainer - Always use ChartContainer with className="h-[300px] w-full" (never raw ResponsiveContainer)
2. ChartWidget - Wrap in ChartWidget for consistent card layout and empty states
3. CSS Variables - Use var(--chart-N) for colors (1-6 available)
4. Axis styling - Use tickLine={false} axisLine={false} className="text-xs" for clean axes
5. Grid - Use <CartesianGrid vertical={false} strokeDasharray="3 3" className="stroke-default-200" />
6. Tooltips - Use shadcn <ChartTooltip content={<ChartTooltipContent />} />
7. Memoize - Use useMemo for chart config and data transformations

References

• Recharts: Use Context7 for latest docs
• Design Language System: See design-language-system skill for colors
• Chart component source: packages/ui/src/components/chart.tsx
• Widget component: apps/web/src/components/charts/widget.tsx