Using an Integrated Development Environment (IDE) makes it easier to find your way in the ROS cpp code. All functions, variables, classes, etc. will be highlighted and can be be easily tracked.
From the suggestions in http://wiki.ros.org/IDEs, we recommend to use KDevelop. Install it first:
sudo apt-get install kdevelop
To set it up and open a ROS project, either a whole catkin workspace or a package, follow carefully the instructions here http://wiki.ros.org/IDEs#kDevelop.
It is recommended to also install doxygen http://www.stack.nl/~dimitri/doxygen/. You can use doxygen comment style to later automatically generate documentation for your source code. Moreover doxygen can generate class dependency graphs that will help you in understanding existing source code. Follow the documentation in the website to learn how to generate documentation, the use of the doxywizard command is especially recommended.
and follow the instructions.
- Line numbers can be added at Setting->Configure Editor->Appearance->Borders.
- The background of your editor can be changed via Setting->Configure Editor->Fonts & Colors -> Default schema for KDevelop.
A list of shortcuts can be found at cheatography or be set to your own preferences at settings->configure shortsuts