Function readCompositionDimensions

packages/cli/src/commands/render.ts:1051–1066

* Read a composition's dimensions from the SAME source the producer's compiler * uses — `data-width` / `data-height` on the `[data-composition-id]` root (see * htmlCompiler.ts). Returns `undefined` when they can't be determined (no root, * missing/invalid attrs, unparseable HTML). Note the produc

(
  compositionHtml: string,
)

 * hook over its timeout — see the note on `renderLocal browser GPU config`).
 */
async function readCompositionDimensions(
  compositionHtml: string,
): Promise<{ width: number; height: number } | undefined> {
  try {
    const { ensureDOMParser } = await import("../utils/dom.js");
    ensureDOMParser();
    const doc = new DOMParser().parseFromString(compositionHtml, "text/html");
    const rootEl = doc.querySelector("[data-composition-id]");
    const width = parseInt(rootEl?.getAttribute("data-width") ?? "", 10);
    const height = parseInt(rootEl?.getAttribute("data-height") ?? "", 10);
    if (width > 0 && height > 0) return { width, height };
  } catch {
    // Unreadable / unparseable composition — fall through to `undefined`.
  }
  return undefined;
}

/**
 * Render pre-flight: return an actionable message when the chosen