Building React Quill Canvases

Building React + Quill canvases

The whole application is one React/TSX file (src/canvas.tsx in the source project). It must export default a single React component that takes no props — the host mounts it. Do not import react-dom or call createRoot.

Start from the working scaffold in references/starter-scaffold.md on a first build: it already wires the date picker, theme tokens, per-query loading state (every card fills in independently as its own data lands), and correct typed-node result reading. Keep that wiring; replace the sample metrics and layout.

Imports

Use React, Quill, Recharts, Lucide, and Day.js for the standard application shell. The platform also admits ten optional libraries for specialized work. Read references/platform-libraries.md before choosing one.

PostHog data comes through import { ph } from "@posthog/canvas-sdk" — a platform-provided module, so it needs no dependencies entry. The same object exists as the window.ph global (how existing canvases reach it); prefer the import in new code.

Other bare imports, dynamic import(), require(), <script> tags, and remote code fail validation. Direct network requests and external images, fonts, media, or frames require an exact HTTPS origin in capabilities.network.origins. They work only in the published canvas — the edit-mode preview blocks direct network access regardless of declaration. Stylesheets from declared origins are allowed; remote scripts remain blocked, so bundle code with the canvas.

Quill component rules

A PostHog data board must be built entirely from @posthog/quill components — never a native control or a styled <div> standing in for one:

• Dropdown/picker → Select (never a native <select>); button → Button (never <button>); text field → Input/Textarea; checkbox → Checkbox; label → Label.
• Table → Table (TableHeader > TableRow > TableHead, then TableBody > TableRow > TableCell); panel → Card (CardHeader + CardTitle + CardContent); pill → Badge; titles → Heading; body → Text.
• The only non-Quill tags allowed are plain layout <div>s and recharts elements.
• Quill is built on Base UI: compose compound parts (Select + SelectTrigger/SelectContent/SelectItem), use controlled value + onValueChange, and swap a part's element with the render prop (e.g. <PopoverTrigger render={<Button …/>} />) instead of wrapping it.
• Quill components are already themed — never restyle one with Tailwind classes or inline style; use their variant/size props. Put layout utilities (flex, grid, gap-4, p-4) on your own wrapper <div>s.
• Buttons: default to variant="outline"; variant="primary" for the one main action only.

Styling and theme

• Give the canvas's outermost element h-screen (height: 100vh) so it fills the iframe viewport. Do not use h-full there: a published canvas's artifact shell gives its html, body, and #root elements no explicit height, so a percentage root height collapses to content height. Nested elements may use h-full once their parent establishes a height.
• Style with Tailwind utilities and Quill components; reserve inline style for genuinely dynamic runtime values (fixed sizes use arbitrary-value utilities like h-[280px]).
• Write specific interface copy. Never use lorem ipsum or placeholder labels in a finished canvas.
• The canvas follows the user's PostHog theme; a .dark class on the document root flips at runtime. Color only from the design-token utilities — surfaces bg-background bg-card bg-muted bg-primary bg-success bg-warning bg-info bg-destructive; text text-foreground text-muted-foreground text-card-foreground; borders border-border. Never a hardcoded hex or light-only color.
• Status tokens invert the usual convention: the bare token (bg-success) is a pale background fill and -foreground (text-success-foreground) is the strong readable color. Colored text or icons always use the -foreground utility; a filled pill pairs bg-success text-success-foreground. Prefer the Quill Badge (variant="success"/"destructive") for deltas so you don't hand-pick.
• bg-secondary, text-secondary, bg-accent, and bg-popover are not defined in the canvas — avoid them.
• recharts strokes/fills use token CSS variables (stroke="var(--primary)", grid/axes in var(--border)/var(--muted-foreground)).
• Write Unicode glyphs (curly quotes, ellipsis, arrows, emoji) as literal characters in JSX — \uXXXX escapes render verbatim in JSX text.

Loading, error, and empty states

Every data point renders a skeleton in its own Card while loading or refreshing: SkeletonText (matching lines and text-size className) for text/number values, Skeleton for blocks/charts.

Render progressively — each query owns its loading state. The chrome (heading, date picker, card frames with skeletons inside) renders immediately, every independent query fires concurrently on mount, and each card swaps its skeleton for data the moment its own query resolves, so a slow query only holds back its own card. Never drive the whole canvas off one shared loading flag or a Promise.all across independent queries — that makes the fastest metric wait for the slowest. Set each section's loading state true again on refresh; never show a blank or a jumping layout. Content the first paint doesn't show (an inactive tab, a collapsed section, a drill-down) defers its query until the user reveals it.

A failed query and an empty result are different states — never let one render as the other. .catch on every ph.query/ph.loadInsight must set an error state that renders visibly (the message plus a Retry button wired to the refresh nonce, as in the starter scaffold), not fall through to zeros, an empty chart, or a "no data yet" message. A query that silently swallows its error makes real breakage (a missing table, an auth failure, a bad query) look like missing data. Reserve the empty state for a query that succeeded with no rows.

Data-product patterns

Treat these as starting shapes and adapt them to the request and available data.

Product dashboard

• Build a live board from verified PostHog data, never a static mockup.
• Start with a Heading, then a responsive grid of compact Card KPIs, trend charts, and useful breakdown tables.
• Show a Badge delta for KPIs when a meaningful comparison period exists.
• Use a LineChart for time series and a BarChart for discrete categories. Do not turn every result into a table.
• Give every KPI, chart, and table its own loading, empty, and error state.
• Make every figure verifiable: an insight-backed card gets a "View in PostHog" affordance opening its saved insight (ph.openExternal with a URL minted by generate-app-url); an ad-hoc ph.query card gets a "View query" Dialog or Collapsible showing the exact query that ran — see "Verifiability" in querying-canvas-data.

Web analytics board

Use this shape when the request or legacy requested pattern says web-analytics:

1. Show Visitors, Page views, Sessions, Session duration, and Bounce rate as KPI cards, with deltas against the previous equal-length period.
2. Plot unique visitors over time, with a second line for the previous period when comparison data is available.
3. Follow with compact tables for top paths, traffic sources or channels, devices, and geography.
4. Prefix countries with flag emoji. Add retention or active-hours views only when the available data makes them useful.

Use the web analytics query kinds described in querying-canvas-data; do not recreate bounce rate, sessionization, attribution, or unique visitors in HogQL. Format large values for display, such as 236K, while preserving the raw value for calculations and accessible labels.

Interactive explorer

Use controlled Quill inputs for each dimension, event, or date choice. Keep result sets small and refresh every dependent query when a control changes.

Checklist or runbook

For a checklist, QA runbook, launch plan, onboarding sequence, or any list of steps people work through and tick off, start from the complete, validated project in references/checklist-example.md. Its load-bearing parts — the typed content module separate from the component, one shared ph.state key per step, the debounced ref-alongside-state update path, an expected outcome on every step, and visible load/save failure states — are what break when improvised. Keep them; replace the content.

Date window

A data board owns its own date control — render Quill's DateTimePicker (never a custom Select or native date input) inside a Popover whose trigger is a Quill Button. PopoverContent gets exactly className="w-auto p-0" and nothing is added to DateTimePicker beyond value/onApply/onCancel (it self-sizes; don't pass compact or widths). Re-run every query when the window changes — see the querying-canvas-data skill for feeding it into dateRange.

State and actions

Persisting values across reloads (ph.state, with user/shared scopes) and writing into PostHog from a button (ph.actions.invoke, e.g. filing a task or an annotation) have their own API contracts, capability declarations, and gesture rules — read the "Runtime memory" and "PostHog writes" sections of the querying-canvas-data skill before using either. Wire actions to a Button onClick that disables itself while the call is in flight, and render the returned error (they are real PostHog writes, throttled server-side).