PreviewManager::prepareRenderParameters

protected function prepareRenderParameters($file): array
{
	$getContentType = function() use ($file){
		$filePreviewData = $this->getViewFileData($file);
		if (!$filePreviewData)
		{
			return null;
		}

		return $filePreviewData['CONTENT_TYPE'];
	};

	$getSourceUri = function() use ($file){
		$filePreviewData = $this->getViewFileData($file);
		if (!$filePreviewData)
		{
			return null;
		}

		return $this->getSourceUri()->addParams([
			self::GET_KEY_TO_SEND_PREVIEW_CONTENT => $this->signFileId($filePreviewData['ID']),
		]);
	};

	return [
		'alt' => [
			'contentType' => $getContentType->bindTo($this, $this),
			'sourceUri' => $getSourceUri->bindTo($this, $this),
		],
	];
}