<cat>Dev</cat> Binary modules allow you to extend Lua's functionality using C++. # Headers The headers you need and an example are [available here](https://github.com/Facepunch/gmod-module-base/tree/development). # Building To turn the example into a visual studio project you should download [premake4](https://github.com/premake/premake-core), place the premake5.exe file in the same directory as BuildProjects.bat (or ideally in your main windows folder), and then run BuildProjects.bat. This will then create a folder called "windows-vs2010", which contains the Visual Studio project file. Read up on how to use [Premake](https://github.com/premake/premake-core/wiki) to compile your modules for osx/linux. # A note on userdata & metatables Userdata and metatables are handled differently in Garry's Mod. This helps the engine determine userdata type much faster. First create your metatable (ideally in GMOD_MODULE_OPEN), then create a reference to it and store it globally in a variable. ``` LUA->CreateTable(); ```⤶ ⤶ ```⤶ ⤶ LUA->PushCFunction(gcDeleteWrapper);⤶ ⤶ LUA->PushCFunction(gcDeleteWrapper); LUA->SetField(-2, "__gc"); ```⤶ ⤶ ```⤶ ⤶ LUA->PushCFunction(toStringWrapper);⤶ ⤶ LUA->PushCFunction(toStringWrapper); LUA->SetField(-2, "__tostring"); ```⤶ ⤶ ```⤶ ⤶ LUA->PushCFunction(indexWrapper);⤶ ⤶ LUA->PushCFunction(indexWrapper); LUA->SetField(-2, "__index"); ```⤶ ⤶ ```⤶ ⤶ LUA->PushCFunction(newIndexWrapper);⤶ ⤶ LUA->PushCFunction(newIndexWrapper); LUA->SetField(-2, "__newindex"); ```⤶ ⤶ ```⤶ ⤶ metatable = LUA->ReferenceCreate();⤶ ⤶ metatable = LUA->ReferenceCreate(); ``` To push your userdata to the stack: ``` GarrysMod::Lua::UserData* ud = ( GarrysMod::Lua::UserData* )LUA->NewUserdata( sizeof( GarrysMod::Lua::UserData ) ); ud->data = pointer_to_your_c_class; ud->type = your_type_id; LUA->ReferencePush( metatable ); LUA->SetMetaTable(-2); ``` To get your userdata from the stack: ``` GarrysMod::Lua::UserData* obj = (GarrysMod::Lua::UserData* )LUA->GetUserdata(position); your_c_class* var = (your_c_class*)(obj->data); ``` # Naming & Location The module files should be placed in the garrysmod/lua/bin/ folder. The names differ between platform and Lua realm. * gmcl_example_win32.dll - windows clientside module * gmsv_example_win32.dll - windows serverside/menu state module * gmcl_example_osx.dll - osx clientside module * gmsv_example_linux.dll - linux serverside/menu state module # Converting From GMod 12 The interface in GMod 13 is very different to that of GMod 12 - the handy object wrappers are gone and the interface is very very similar to the standard Lua C API. Infact, nearly all of the functions in the interface work exactly the same way as their equivalents in the Lua C API, they're just named slightly differently. You should be able to work out what most of the functions do from the example and the [Lua C API Documentation](http://www.lua.org/manual/5.2/manual.html#4.8). If you find this kind of stack-level programming too hard, BlackAwps has created some "backwards headers", which should work exactly how the GMod 12 interface worked, you can find them [here](https://bitbucket.org/breakpointservers/bkacjios-glua-modules/src).