# CellRendererBackend

Source: /tuil/docs/reference/packages/cell/api/cell-renderer-backend
Locale: en

class exported by @mwillbanks/tuil-cell.



{/* Generated by tooling/docs/generate-reference.ts. */}

## class [#class]

Public class exported by `@mwillbanks/tuil-cell`.

```ts
export class CellRendererBackend implements RendererBackend<CellTree> {
  readonly id = "cell";
  readonly capabilities = new Set([
    "cells",
    "renderer-application",
    "pointer",
    "scroll",
    "clipboard",
    "alternate-screen",
    "inline",
    "static",
    "json",
    "silent",
    "embedded",
  ] as const);
  #accelerator = typescriptCellAccelerator;
  readonly #acceleratorReady: Promise<void>;
  #sequence = 0;

  constructor(options: CellRendererBackendOptions = {}) {
    const configured = options.accelerator ?? typescriptCellAccelerator;
    this.#acceleratorReady = Promise.resolve(
      typeof configured === "function" ? configured() : configured,
    ).then((accelerator) => {
      this.#accelerator = accelerator;
    });
  }

  async render(
    tree: CellTree,
    context: RendererContext,
  ): Promise<RendererFrame> {
    await this.#acceleratorReady;
    if (context.signal.aborted) throw context.signal.reason;
    const projected =
      typeof tree === "function"
        ? await this.#renderFunction(tree, context)
        : "lines" in tree
          ? this.#renderScene(tree, context)
          : "kind" in tree
            ? composeCellScene(
                tree,
                context.capabilities.width,
                context.capabilities.height,
                context.layout,
              )
            : tree;
    const frame = normalizeCellFrame(
      projected,
      context.capabilities.hyperlinks,
    );
    return Object.freeze({
      width: frame.width,
      height: frame.height,
      sequence: ++this.#sequence,
      timestamp: performance.now(),
      mode: context.mode,
      payload: frame,
      cursor: frame.cursor,
    });
  }

  diff(
    previous: RendererFrame | undefined,
    current: RendererFrame,
  ): RendererOutput {
    const mode = current.mode ?? "interactive";
    if (mode === "interactive") {
      return this.#accelerator.diff(
        previous?.payload as CellFrame | undefined,
        current.payload as CellFrame,
      );
    }
    return encodeCellOutput(
      current.payload as CellFrame,
      mode === "json" ? "json" : mode === "silent" ? "silent" : "static",
      previous?.payload as CellFrame | undefined,
    );
  }

  #renderScene(tree: RendererScene, context: RendererContext): CellFrame {
    const scene = normalizeRendererScene(
      tree,
      context.capabilities.width,
      context.capabilities.height,
      context.capabilities.hyperlinks,
    );
    const buffer = new CellBuffer(
      context.capabilities.width,
      context.capabilities.height,
    );
    for (const [index, line] of scene.lines.entries()) {
      if (index >= buffer.height) break;
      const runs = scene.styledLines?.[index];
      if (!runs || runs.length === 0) {
        buffer.write(0, index, line);
        continue;
      }
      let column = 0;
      for (const run of runs) {
        column = buffer.write(
          column,
          index,
          run.text,
          rendererCellStyle(run.style, run.link),
        );
      }
    }
    buffer.setCursor(scene.cursor);
    return Object.freeze({ ...buffer.frame(), semantics: scene.semantics });
  }

  async #renderFunction(
    tree: (
      buffer: CellBuffer,
      context: RendererContext,
    ) => void | Promise<void>,
    context: RendererContext,
  ): Promise<CellFrame> {
    const buffer = new CellBuffer(
      context.capabilities.width,
      context.capabilities.height,
    );
    await tree(buffer, context);
    if (context.signal.aborted) throw context.signal.reason;
    return buffer.frame();
  }
}
```

## Members [#members]

| Member              | Type                                                                                                                                                               | Required | Description                                                                                                                                                                                                     | Related types                                                                                                              |
| ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------- |
| `id`                | `"cell"`                                                                                                                                                           | Yes      | The `id` member uses the `"cell"` contract.                                                                                                                                                                     | —                                                                                                                          |
| `capabilities`      | `Set<"static" \| "json" \| "silent" \| "cells" \| "renderer-application" \| "pointer" \| "scroll" \| "clipboard" \| "alternate-screen" \| "inline" \| "embedded">` | Yes      | The `capabilities` member uses the `Set<"static" \| "json" \| "silent" \| "cells" \| "renderer-application" \| "pointer" \| "scroll" \| "clipboard" \| "alternate-screen" \| "inline" \| "embedded">` contract. | —                                                                                                                          |
| `#accelerator`      | `CellAccelerator`                                                                                                                                                  | Yes      | The `#accelerator` member uses the `CellAccelerator` contract.                                                                                                                                                  | [`CellAccelerator`](/tuil/docs/reference/packages/cell/api/cell-accelerator)                                                    |
| `#acceleratorReady` | `Promise<void>`                                                                                                                                                    | Yes      | The `#acceleratorReady` member uses the `Promise<void>` contract.                                                                                                                                               | —                                                                                                                          |
| `#sequence`         | `number`                                                                                                                                                           | Yes      | The `#sequence` member uses the `number` contract.                                                                                                                                                              | —                                                                                                                          |
| `__constructor`     | `any`                                                                                                                                                              | Yes      | The `__constructor` member uses the `any` contract.                                                                                                                                                             | —                                                                                                                          |
| `render`            | `(tree: CellTree, context: RendererContext) => Promise<RendererFrame>`                                                                                             | Yes      | The `render` member uses the `(tree: CellTree, context: RendererContext) => Promise<RendererFrame>` contract.                                                                                                   | [`CellTree`](/tuil/docs/reference/packages/cell/api/cell-tree)                                                                  |
| `diff`              | `(previous: RendererFrame \| undefined, current: RendererFrame) => RendererOutput`                                                                                 | Yes      | The `diff` member uses the `(previous: RendererFrame \| undefined, current: RendererFrame) => RendererOutput` contract.                                                                                         | —                                                                                                                          |
| `#renderScene`      | `(tree: RendererScene, context: RendererContext) => CellFrame`                                                                                                     | Yes      | The `#renderScene` member uses the `(tree: RendererScene, context: RendererContext) => CellFrame` contract.                                                                                                     | [`CellFrame`](/tuil/docs/reference/packages/cell/api/cell-frame)                                                                |
| `#renderFunction`   | `(tree: (buffer: CellBuffer, context: RendererContext) => void \| Promise<void>, context: RendererContext) => Promise<CellFrame>`                                  | Yes      | The `#renderFunction` member uses the `(tree: (buffer: CellBuffer, context: RendererContext) => void \| Promise<void>, context: RendererContext) => Promise<CellFrame>` contract.                               | [`CellBuffer`](/tuil/docs/reference/packages/cell/api/cell-buffer), [`CellFrame`](/tuil/docs/reference/packages/cell/api/cell-frame) |

## Parameters [#parameters]

This declaration has no public members.

## Returns [#returns]

This declaration does not return a value.

## Throws [#throws]

No thrown errors are documented for this declaration.

## Related types [#related-types]

* [`CellBuffer`](/tuil/docs/reference/packages/cell/api/cell-buffer)
* [`CellFrame`](/tuil/docs/reference/packages/cell/api/cell-frame)
* [`CellRendererBackendOptions`](/tuil/docs/reference/packages/cell/api/cell-renderer-backend-options)
* [`CellTree`](/tuil/docs/reference/packages/cell/api/cell-tree)

## Source [#source]

[View the secondary source reference](https://github.com/mwillbanks/tuil/blob/main/packages/cell/src/index.ts)

## Package [#package]

[@mwillbanks/tuil-cell](/tuil/docs/reference/packages/cell)