public function filter_context_locations( $locations ) {
		if ( ! is_array( $locations ) ) {
			return $locations;
		}

		// The state of the whole Filter Bar. If found then it will be one of `open` or `closed`.
		$locations['fbar_state'] = [
			'read' => [
				Context::FUNC => [
					static function () {
						$var = tribe_get_request_var( 'tribe_filter_bar_state', Context::NOT_FOUND );
						if ( Context::NOT_FOUND === $var ) {
							return $var;
						}

						return tribe_is_truthy( $var ) ? 'open' : 'closed';
					},
				],
			],
		];

		// The state of each Filter Bar filter, an integer representing a bitmask.
		$locations['fbar_filters_state'] = [
			'read' => [
				Context::REQUEST_VAR => [ 'tribe_filters_state' ],
			],
		];

		// Add some extra locations to read the current and previous URL from.
		foreach ( [ 'view_url' => 'url', 'view_prev_url' => 'prev_url' ] as $location => $request_var ) {
			if ( isset( $locations[ $location ]['read'] ) ) {
				$prev = Arr::get( $locations[ $location ]['read'], Context::REQUEST_VAR, [] );

				$locations[ $location ]['read'][ Context::REQUEST_VAR ] = array_merge( $prev, [ $request_var ] );
			}
		}

		return $locations;
	}