The original GMapping SLAM (see (https://openslam-org.github.io/gmapping.html), http://wiki.ros.org/slam_gmapping and https://github.com/ros-perception/slam_gmapping) was modified to also inform the region visited by the robot.
The project is compiled using catkin. From the project root directory:
catkin_make
source devel/setup.bash
roslaunch gmapping gmapping.launch