BBP_BuddyPress_Activity::activity_forums_scope( array $retval = array(), array $filter = array() )

		public function activity_forums_scope( $retval = array(), $filter = array() ) {

			// Determine the user_id.
			if ( ! empty( $filter['user_id'] ) ) {
				$user_id = $filter['user_id'];
			} else {
				$user_id = bp_displayed_user_id()
					? bp_displayed_user_id()
					: bp_loggedin_user_id();
			}

			$forum_ids = bbp_get_user_subscribed_forum_ids( $user_id );
			$topic_ids = bbp_get_user_subscribed_topic_ids( $user_id );

			if ( empty( $forum_ids ) ) {
				$forum_ids = array( 0 );
			}

			if ( empty( $topic_ids ) ) {
				$topic_ids = array( 0 );
			}

			$retval = array(
				'relation' => 'AND',
				array(
					'column'  => 'component',
					'compare' => '=',
					'value'   => 'bbpress',
				),
				array(
					'relation' => 'OR',
					array(
						'column'  => 'secondary_item_id',
						'compare' => 'IN',
						'value'   => (array) $forum_ids,
					),
					array(
						'column'  => 'secondary_item_id',
						'compare' => 'IN',
						'value'   => (array) $topic_ids,
					),
				),

				// we should only be able to view sitewide activity content for those the user.
				// is following.
				array(
					'column' => 'hide_sitewide',
					'value'  => 0,
				),

			);

			return $retval;
		}