# Custom view rules

What custom view code may and may not contain, generated from the SDK validator.

## Custom view rules
Custom view code is checked before it runs. These rules come straight from the validator:

- **HTML elements:** only `div`, `section`, `article`, `header`, `footer`, `main`, `aside`, `nav`, `h1`, `h2`, `h3`, `h4`, `p`, `span`, `strong`, `em`, `i`, `small`, `br`, `hr`, `label`, `input`, `textarea`, `button`, `select`, `option`, `optgroup`, `fieldset`, `legend`, `output`, `progress`, `meter`, `ul`, `ol`, `li`, `dl`, `dt`, `dd`, `figure`, `figcaption`, `img`, `video`, `audio`, `source`, `canvas`, `table`, `thead`, `tbody`, `tfoot`, `tr`, `th`, `td`, `pre`, `code`, `details`, `summary`. No scripts, iframes, SVG, forms, comments or inline event attributes; media URLs must be `data:` or `blob:`.
- **Never use these names in view JavaScript:** `eval`, `Function`, `AsyncFunction`, `GeneratorFunction`, `require`, `importScripts`, `process`, `globalThis`, `window`, `self`, `top`, `parent`, `opener`, `frames`, `location`, `navigation`, `history`, `navigator`, `localStorage`, `sessionStorage`, `indexedDB`, `caches`, `cookieStore`, `fetch`, `XMLHttpRequest`, `WebSocket`, `EventSource`, `Worker`, `SharedWorker`, `ServiceWorker`, `WebAssembly`, `Deno`, `Bun`, `Reflect`, `Proxy`, `DOMParser`, `MutationObserver`, `postMessage`, `open`, `close`, `print`, `alert`, `confirm`, `prompt`, `setInterval`, `setTimeout`, `queueMicrotask`, `arguments`, `constructor`, `__proto__`, `prototype`, `__lookupGetter__`, `__lookupSetter__`, `__defineGetter__`, `__defineSetter__`, `getPrototypeOf`, `setPrototypeOf`, `getOwnPropertyDescriptor`, `getOwnPropertyDescriptors`, `getOwnPropertyNames`, `getOwnPropertySymbols`, `defineProperty`, `defineProperties`, `defaultView`, `ownerGlobal`, `contentWindow`, `contentDocument`, `cookie`, `domain`, `documentURI`, `URL`, `baseURI`, `referrer`, `write`, `writeln`, `innerHTML`, `outerHTML`, `insertAdjacentHTML`, `createElement`, `createElementNS`, `createContextualFragment`, `createRange`, `setAttribute`, `setAttributeNS`, `attributes`, `attributeStyleMap`, `adoptNode`, `importNode`, `execCommand`, `replaceChildren`, `setHTML`, `setHTMLUnsafe`, `parseHTML`, `parseHTMLUnsafe`, `showSaveFilePicker`, `showDirectoryPicker`, `saveAs`, `FileSystemWritableFileStream`, `createWritable`, `msSaveBlob`, `msSaveOrOpenBlob`, `download`.
- **Never use these property names:** `assign`, `values`, `entries`, `fromEntries` (so no `Object.assign`, `Object.values`, `Object.entries`, `Object.fromEntries`; use arrays and `map`/`forEach`).
- **These words may not appear anywhere in view JavaScript, even in strings or comments:** `style`, `cssText`, `setProperty`, `removeProperty`, `insertRule`, `deleteRule`, `styleSheets`, `adoptedStyleSheets`, `animate`. Change appearance with CSS classes and `hidden`; put colors in the stylesheet.
- **Property access with brackets needs a literal key:** `items[0]` and `record["title"]` are accepted; `items[index]` is rejected. Iterate with `map`/`forEach` or call `items.at(index)`.
- **No named recursive functions** and no listeners on the global frame; attach events to declared controls.
- **Dynamic elements:** `StillMade.render` can create `div`, `section`, `article`, `header`, `footer`, `p`, `span`, `strong`, `em`, `i`, `small`, `h1`, `h2`, `h3`, `h4`, `label`, `button`, `input`, `textarea`, `select`, `option`, `ul`, `ol`, `li`, `table`, `thead`, `tbody`, `tr`, `th`, `td`, `details`, `summary`, `output`, `progress`, `img`; give repeated items stable IDs derived from their identity. An `img` gets its picture when you set its `src` to the data URL `StillMade.previewImage` returns, after rendering; the renderer keeps Block-owned `src`. `previewImage` works on items of an `image[]` input.
- **Shared writes are queued in order:** if one `StillMade.updateShared` write is rejected (conflict, read-only or timeout), the writes queued behind it are rejected too. Send dependent edits one at a time or through `StillMade.scheduleSharedEdit`, keep the person's draft, and retry from the latest `onShared` value. `{merge: true}` merges independent fields of an object value; create an absent field with the precondition `{exists: false}`.
- **Limits:** HTML 64 KiB, CSS 32 KiB, JavaScript 64 KiB; 30 runs and 60 image previews per minute.