From DDraceNetwork
    This page contains changes which are not marked for translation.
    Other languages:

    This article aims to introduce you into DDNet development, since it's an open-source game, it relies on random people kind enough to contribute to it on their free time.

    Your development environment[edit | edit source]

    It is extremely recommended to set up a Linux environment to begin programming in DDNet for the following reasons (as of now):

    • Most DDNet contributors actually use Linux to contribute.
    • Easier package management, you can easily install all the needed libraries and begin contributing.
    • This article doesn't have yet a Windows version and is focused on Linux.

    First an foremost, DDNet is coded using the C++ programming language, you will need to be fairly familiar with it, but you can also know the basics and learn more with it.

    Some useful resources to learn C++:

    The source code of DDNet is managed using Git, a version control system, an essential tool to collaborate with multiple developers.

    If you don't have git yet in your Linux distribution, make sure to install it, for example in most debian/ubuntu based distributions: sudo apt install git.

    Getting the source code[edit | edit source]

    The source code is located on Github, you can get the source code by cloning without the need of an account, but if you want to ever put your changes to the official source code you will need one.

    If you are not familiar with git/github you can learn the basics here: Hello World - Github

    Installing the dependencies[edit | edit source]

    If you are on Linux, you can install all the needed dependencies by reading the README on the DDNet github page:

    For Arch Linux:

    sudo pacman -S --needed base-devel cmake curl freetype2 git glew gmock libnotify opusfile python sdl2 sqlite wavpack

    Compiling DDNet[edit | edit source]

    We use CMake to control the compilation process, if you have all the dependencies installed, it's as easy as following these commands (make sure you are on the DDNet folder):

    mkdir build
    cd build
    cmake ..
    make -j$(nproc)

    General information[edit | edit source]

    Here are some general bits of information:

    • Currently, the source code is compiled with the C++17 standard, but you will see that many parts of the code are more C-like since only mostly new code uses C++17 stuff.
    • std::string is rarely used, char arrays plus using system.h methods for handling them are the norm.
    • Most I/O code, formatting and printing is done using system.h provided methods.

    The source code layout[edit | edit source]

    Now that you can build DDNet you can begin editing it.

    The src/base directory[edit | edit source]

    Since DDNet is a cross-platform game, an abstraction layer over that is needed to make development easier, this directory contains many useful functions to handle that.

    The src/engine directory[edit | edit source]

    Here lies the game engine, it handles most stuff that is not gameplay related, such as graphics, sound, network, etc.

    The src/game directory[edit | edit source]

    All gameplay related code is here, separated into client and server.

    Server side[edit | edit source]

    This game uses its own hierarchical object-oriented entity system, the main class to which all other entities derive from is CEntity located in src/game/server/entity.h.

    These entities are managed by the game world located here src/game/server/gameworld.h

    Some important entities are:

    • CCharacter: Represents a tee that is alive, it is instantiated when a tee spawns and deleted when it dies. For information about the player kept between deaths, see CPlayer.

    Client side[edit | edit source]

    The client side is made up of components, these are classes that inherit CComponent: These components can implement the virtual methods such as OnInit, OnMessage, etc. to provide their functionality.

    Networking[edit | edit source]

    The network protocol is mostly generated by python scripts that output C++ code, for example, datasrc/ defines all network packets.

    Code conventions[edit | edit source]

    The ongoing discussion on code conventions is located here: ddnet#2945

    Currently, the following applies:

    Indentation style[edit | edit source]

    Allman style is used.

    This style puts the brace associated with a control statement on the next line, indented to the same level as the control statement. Statements within the braces are indented to the next level.

    while(x == y)

    Classes and Structs[edit | edit source]

    Must be prefixed by C (for legacy reasons this is ignored for structs in some places, such as in graphics code) or I for interfaces.


    class CCharacter : public CEntity
        // ...

    Enums and constants[edit | edit source]

    Should be screaming snake case, for example: MAX_PLAYERS


    Variable naming[edit | edit source]

    • The names of variables contain 3 parts: qualifier, prefix and name.
    • Variable names should start with uppercase unless they are 1 char long without any prefix or qualifier, for example: i, x, y.
    • Variables can have more than 1 qualifier (or zero) and more than 1 prefix (or zero).

    These are laid out like this: [qualifiers]_[prefixes][Name]

    Qualifiers[edit | edit source]

    • m for member variables: m_MyVariable.
    • s for static variables: s_MyStaticVariable.
    • g for global variables with external linkage: gs_MyGlobalStaticVar.

    Prefixes[edit | edit source]

    • p for pointers: pMyPointer, m_pCharacter, ppMyPointerToPointer.
    • a for arrays: aMyArray, aBuf.
    • fn for functions: pfnMyCallback, m_papfnMyPointerToArrayOfCallbacks.

    Common snippets[edit | edit source]

    Here is a list of code that you may frequently see across the codebase:

    Formatting text[edit | edit source]

    char aBuf[128];
    str_format(aBuf, sizeof(aBuf), "number: %d", 2);

    Iterating over all players[edit | edit source]

    for(int i = 0; i < MAX_CLIENTS; i++)
        // Server-side
        CPlayer *pPlayer = GameServer()->m_apPlayers[i];

    Printing to the game console[edit | edit source]

    Console()->Print(IConsole::OUTPUT_LEVEL_STANDARD, "wikiprint", "Hello from the ddnet wiki!");

    Debug printing[edit | edit source]

    int i = 2;
    dbg_msg("wikiprint", "Hello from the ddnet wiki: %d", i);

    External resources[edit | edit source]