/**
	 * Prepares array entry for widget field, ready to be passed to CDashboard API functions.
	 * Reference is needed here to avoid array merging in CWidgetForm::fieldsToApi method. With large number of widget
	 * fields it causes significant performance decrease.
	 *
	 * @param array $widget_fields  Reference to array of widget fields.
	 */
	public function toApi(array &$widget_fields = []) {
		$value = $this->getValue();

		$dataset_fields = [
			'color' => ZBX_WIDGET_FIELD_TYPE_STR,
			'type' => ZBX_WIDGET_FIELD_TYPE_INT32,
			'width' => ZBX_WIDGET_FIELD_TYPE_INT32,
			'pointsize' => ZBX_WIDGET_FIELD_TYPE_INT32,
			'transparency' => ZBX_WIDGET_FIELD_TYPE_INT32,
			'fill' => ZBX_WIDGET_FIELD_TYPE_INT32,
			'axisy' => ZBX_WIDGET_FIELD_TYPE_STR,
			'timeshift' => ZBX_WIDGET_FIELD_TYPE_STR,
			'missingdatafunc' => ZBX_WIDGET_FIELD_TYPE_INT32,
			'aggregate_function' => ZBX_WIDGET_FIELD_TYPE_INT32,
			'aggregate_interval' => ZBX_WIDGET_FIELD_TYPE_STR,
			'aggregate_grouping' => ZBX_WIDGET_FIELD_TYPE_INT32
		];
		$dataset_defaults = self::getDefaults();

		foreach ($value as $index => $val) {
			// Hosts and items fields are stored as arrays to bypass length limit.
			foreach ($val['hosts'] as $num => $pattern_item) {
				$widget_fields[] = [
					'type' => ZBX_WIDGET_FIELD_TYPE_STR,
					'name' => $this->name.'.hosts.'.$index.'.'.$num,
					'value' => $pattern_item
				];
			}
			foreach ($val['items'] as $num => $pattern_item) {
				$widget_fields[] = [
					'type' => ZBX_WIDGET_FIELD_TYPE_STR,
					'name' => $this->name.'.items.'.$index.'.'.$num,
					'value' => $pattern_item
				];
			}

			// Other dataset fields are stored if different from the defaults.
			foreach ($dataset_fields as $name => $type) {
				if ($val[$name] !== null && $val[$name] != $dataset_defaults[$name]) {
					$widget_fields[] = [
						'type' => $type,
						'name' => $this->name.'.'.$name.'.'.$index,
						'value' => $val[$name]
					];
				}
			}
		}
	}