PreviewUpdateService.renderBlockByIndex

How to read this API

These are TypeScript APIs compiled into SnapTeX; a .tex project cannot load them at runtime.

• function name(...) is a helper that your rule imports and calls.
• apply(...), render(...), extract(...), and collect(...) are callbacks that your rule implements and SnapTeX calls.
• renderer.name(...), context.name(...), input.name(...), and deps.name(...) are methods SnapTeX supplies to callbacks; do not import or construct them.
• service.name(...) is an instance method called after your host or test constructs PreviewUpdateService.

Register extension declarations through SNAP_TEX_RULES in src/rules.ts. See Source API Scope for imports, value ownership, output safety, rebuilds, and testing.

Renders one previously parsed block for lazy or virtualized preview mounting. Call it only after render(..., { deferFullHtml: true }) has established the current block map.

Signature

service.renderBlockByIndex(
    index: number
): Promise<{ hash: string; html?: string } | undefined>

Parameters

Parameter	Description
index	Zero-based block index from the latest render payload

Returns

The block metadata and HTML when the index exists, otherwise undefined. The service automatically selects synchronous legacy rendering or asynchronous AST rendering according to its current backend.

Call relationships

• Requires: a preceding render call to populate document and renderer state.
• Calls: SmartRenderer.renderBlockByIndex or renderBlockByIndexAsync.
• Used by: viewport virtualization and lazy-render tests.

await service.render(uri, source, { deferFullHtml: true });
const block = await service.renderBlockByIndex(0);
assert.match(block?.html ?? '', /First paragraph/);

See also

• PreviewUpdateService.render
• Long Documents