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plugin-dev.md

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This document details how to compile a basic plugin in Visual Studio, MinGW, or GCC/Clang.

To find the functions and variables available for use in plugins, look for CC_API/CC_VAR in the .h files.

Source code of some actual plugins

Setup

You need to download and install either Visual Studio, MinGW, or GCC/Clang.

Note: MinGW/GCC/Clang are relatively small, while Visual Studio is gigabytes in size.
If you're just trying to compile a plugin on Windows you might want to use MinGW. See main readme.

I assume your directory is structured like this:

src/...
TestPlugin.c

Or in other words, in a directory somewhere, you have a file named TestPlugin.c, and then a sub-directory named src which contains the game's source code.

Basic plugin

#include "src/Chat.h"
#include "src/Game.h"
#include "src/String.h"

static void TestPlugin_Init(void) {
        cc_string msg = String_FromConst("Hello world!");
        Chat_Add(&msg);
}

int Plugin_ApiVersion = 1;
struct IGameComponent Plugin_Component = { TestPlugin_Init };

Here's the idea for a basic plugin that shows "Hello world" in chat when the game starts. Alas, this won't compile...

Basic plugin boilerplate

#ifdef _WIN32
    #define CC_API __declspec(dllimport)
    #define CC_VAR __declspec(dllimport)
    #define EXPORT __declspec(dllexport)
#else
    #define CC_API
    #define CC_VAR
    #define EXPORT __attribute__((visibility("default")))
#endif

#include "src/Chat.h"
#include "src/Game.h"
#include "src/String.h"

static void TestPlugin_Init(void) {
    cc_string msg = String_FromConst("Hello world!");
    Chat_Add(&msg);
}

EXPORT int Plugin_ApiVersion = 1;
EXPORT struct IGameComponent Plugin_Component = { TestPlugin_Init };

With this boilerplate, we're ready to compile the plugin. All plugins require this boilerplate, so feel free to copy and paste it.

Writing plugins in C++

Exported plugin functions must be surrounded with extern "C", i.e.

extern "C" {
EXPORT int Plugin_ApiVersion = 1;
EXPORT struct IGameComponent Plugin_Component = { TestPlugin_Init };
}

Otherwise your plugin will not load. (you'll see error getting plugin version in-game)

Compiling

Plugin compilation instructions differs depending on the compiler and operating system

Linux

Compiling using gcc or clang

Cross compiling for Windows 32-bit

Cross compiling for Windows 64-bit

macOS

Compiling using gcc or clang

Windows

Compiling using Visual Studio

Compiling using mingw-w64

Compiling - Linux

Using gcc or clang

Compiling

cc TestPlugin.c -o TestPlugin.so -shared -fPIC

Then put TestPlugin.so into your game's plugins folder. Done.

Cross compiling for Windows 32 bit using mingw-w64

Setup

  1. Create ClassiCube.exe by either:
    1. Compiling the game, see Cross compiling for windows (32 bit) in main readme
    2. Downloading 32 bit ClassiCube from https://www.classicube.net/download/#dl-win
  2. Install the mingw-w64-tools package (if it isn't already)
  3. Generate the list of exported symbols from ClassiCube.exe by running:
    • gendef ClassiCube.exe
  4. Create a linkable library from the exported symbols list by running:
    • i686-w64-mingw32-dlltool -d ClassiCube.def -l libClassiCube.a -D ClassiCube.exe

TODO: also document alternate method of compiling the game using --out-implib

Compiling

i686-w64-mingw32-gcc TestPlugin.c -o TestPlugin.dll -s -shared -L . -lClassiCube

Then put TestPlugin.dll into your game's plugins folder. Done.

Cross compiling for Windows 64 bit using mingw-w64

Setup

  1. Create ClassiCube.exe by either:
    1. Compiling the game, see Cross compiling for windows (64 bit) in main readme
    2. Downloading 64 bit ClassiCube from https://www.classicube.net/download/#dl-win
  2. Install the mingw-w64-tools package (if it isn't already)
  3. Generate the list of exported symbols from ClassiCube.exe by running:
    • gendef ClassiCube.exe
  4. Create a linkable library from the exported symbols list by running:
    • x86_64-w64-mingw32-dlltool -d ClassiCube.def -l libClassiCube.a -D ClassiCube.exe

TODO: also document alternate method of compiling the game using --out-implib

Compiling

x86_64-w64-mingw32-gcc TestPlugin.c -o TestPlugin.dll -s -shared -L . -lClassiCube

Then put TestPlugin.dll into your game's plugins folder. Done.

Compiling - macOS

Using gcc or clang

Compiling

cc TestPlugin.c -o TestPlugin.dylib -undefined dynamic_lookup

Then put TestPlugin.dylib into your game's plugins folder. Done.

Compiling - Windows

Using Visual Studio

TODO more detailed when I have some more time...

Setup

  1. Compile the game, see Compiling - Windows > using Visual Studio in main readme
  2. Find the ClassiCube.lib that was generated when compiling the game. Usually it is in either src\x64\Debug or src\x86\Debug.
  3. Add a new Empty Project to the ClassiCube solution, then add the plugin .c files to it

Note: If the plugin provides a .vcxproj file, you can skip step 2 and just open that project file instead.

Configuration - alternative #1

The simplest way of linking to the .lib file is simply adding the following code to one of the plugin's .c files

#ifdef _MSC_VER
  #ifdef _WIN64
    #pragma comment(lib, "[GAME SRC FOLDER]/x64/Debug/ClassiCube.lib")
  #else
    #pragma comment(lib, "[GAME SRC FOLDER]/x86/Debug/ClassiCube.lib")
  #endif
#endif

replacing [GAME SRC FOLDER] with the full path of src folder (e.g. C:/Dev/ClassiCube/src)

Configuration - alternative #2

The more complicated way of linking to the .lib file is to add it to the plugin's project configuration file

Right click the plugin project in the Solution Explorer pane, then click Properties

TODO: add screenshots here

TODO: may need to configure include directories

  1. In Configuration properties -> General, make sure Configuration type is set to Dynamic library (.DLL)

  2. In Configuration properties -> Linker -> Input, click the dropdown button for Additional Dependencies, then click Edit. Add the full path to ClassiCube.lib, then click OK

Compiling

Build the project. There should be a line in the build output that tells you where you can find the .dll file like this: Project1.vcxproj -> C:\classicube-dev\testplugin\src\x64\Debug\TestPlugin.dll

Then put TestPlugin.dll into your game's plugins folder. Done.

Using mingw-w64

Setup

  1. Create ClassiCube.exe by either:
    1. Compiling the game, see Compiling for windows (MinGW-w64) in main readme
    2. Downloading ClassiCube from https://www.classicube.net/download/#dl-win
  2. Generate the list of exported symbols in ClassiCube.exe by running:
    • gendef ClassiCube.exe
  3. Create a linkable library from the exported symbols list by running:
    • dlltool -d ClassiCube.def -l libClassiCube.a -D ClassiCube.exe

Compiling

gcc TestPlugin.c -o TestPlugin.dll -s -shared -L . -lClassiCube

Then put TestPlugin.dll into your game's plugins folder. Done.

Notes for compiling for Windows

Ensuring your plugin works when the ClassiCube exe isn't named ClassiCube.exe

If you follow the prior compilation instructions, the compiled DLL will have a runtime dependancy on ClassiCube.exe

However, this means that if the executable is e.g. named ClassiCube (2).exe instead. the plugin DLL will fail to load

To avoid this problem, you must

  1. Stop linking to ClassiCube (e.g. for MinGW, remove the -L . -lClassiCube)
  2. Load all functions and variables exported from ClassiCube via GetProcAddress instead

This is somewhat tedious to do - see here for some examples of plugins which do this

Compiling ultra small plugin DLLs - MinGW

If you ONLY use code from the game (no external libraries and no C standard library functions):

  • You can add -nostartfiles -Wl,--entry=0 to the compile flags to reduce the DLL size (e.g from 11 to 4 kb)

This isn't necessary to do though, and plugin DLLs work completely fine without doing this.