# CMake Guide

CMake is an open-source, cross-platform family of tools designed to build, test and package software. CMake is used to control the software compilation process using simple platform and compiler independent configuration files, and generates native makefiles and workspaces that can be used in the compiler environment of your choice.

## Requirement

1. Open your terminal and execute:
  ```sh
  cmake --version
  ```
if the CMake version is lower than 3.1, please upgrade.

2. You should use __out-of-source__ builds, this means you need to create a different directory than __cocos2d-x__ to execute the `cmake` command.

## Step by Step

### Linux

```sh
cd cocos2d-x
mkdir linux-build && cd linux-build
cmake ..
make
``` 

Execute `make help` to see all build targets, `make <target>` build specified target

### Generate Visual Studio projects

```sh
cd cocos2d-x
mkdir win32-build && cd win32-build
cmake .. -G"Visual Studio 15 2017" -Tv141
```

Execute `cmake --build .` to compile, or open __Cocos2d-x.sln__ in Explorer to use the generated project. 

### Generate macOS Project

```sh
cd cocos2d-x
mkdir mac-build && cd mac-build
cmake .. -GXcode
open Cocos2d-x.xcodeproj
```

### Generate iOS Project

```sh
cd cocos2d-x
mkdir ios-build && cd ios-build
cmake .. -GXcode -DCMAKE_TOOLCHAIN_FILE=../cmake/ios.toolchain.cmake
open Cocos2d-x.xcodeproj
```

The default build is for running on actual iOS hardware, if you want to run in the simulator, please add `-DIOS_PLATFORM=SIMULATOR` for architecture i386 or `-DIOS_PLATFORM=SIMULATOR64` for x86_64.

### Android Studio

We use the Gradle for Android applications, and Gradle use cmake to build the native code, see  [gradle.properties](https://github.com/cocos2d/cocos2d-x/blob/84be684e3858393a6f3efc50e3f95d4e0ac92a20/tests/cpp-empty-test/proj.android/gradle.properties#L38): `PROP_NDK_MODE`, it controls how native builds work.

```sh
# android native code build type
# none, native code will never be compiled.
# cmake, native code will be compiled by CMakeLists.txt
# ndk-build, native code will be compiled by Android.mk
PROP_BUILD_TYPE=cmake
```

If you want to add cmake build arguments, please add it at [external Native Build](https://github.com/cocos2d/cocos2d-x/blob/84be684e3858393a6f3efc50e3f95d4e0ac92a20/tests/cpp-empty-test/proj.android/app/build.gradle#L25) block of __app/build.gradle__ file.

## Prebuilt libraries feature

To solve long compilation times of the engine source code one can use prebuilt libraries. Using this feature you only need build engine sources once for a specific environment or again when the engine version changes and you wish to utilize the new version.

### Example

This is an example of building c++ libs once, and use them in different c++ projects.

```sh
cocos new -l cpp -p my.pack.app1 test_app1
mkdir app1_build && cd app1_build
cmake ../test_app1 -DGEN_COCOS_PREBUILT=ON
make prebuilt
```

Change option `GEN_COCOS_PREBUILT` and use instead `USE_COCOS_PREBUILT` to use prebuilt in the same project

```sh
cmake ../test_app1 -DGEN_COCOS_PREBUILT=OFF -DUSE_COCOS_PREBUILT=ON
make TemplateCpp
open bin/TemplateCpp.app
```

Add `-DUSE_COCOS_PREBUILT=ON` to use prebuilt libs in another cmake build.

```sh
cocos new -l cpp -p my.pack.app2 test_app2
mkdir app2_build && cd app2_build
cmake ../test_app2 -DUSE_COCOS_PREBUILT=ON
make TemplateCpp
open bin/TemplateCpp.app
```

> Any other cpp project can use prebuilt in this way

When using the prebuilt libraries on Android there is a small difference as CMake can't find system environment when built using Gradle. You need to [supply a path](https://github.com/cocos2d/cocos2d-x/blob/c087be314c2c56a757bf66163b173746b5d6ad34/tests/cpp-empty-test/proj.android/app/build.gradle#L34) as the location of prebuilt libs.

## Build Options

### CMake Common Build Options

1. __`-G`__, generate native build project you specified, for example

    * `-GXcode` generate Xcode project files.
    * `-GVisual Studio 15 2017` generate Visual Studio 2017 project, the default toolset is v141, add `-T` option to specify toolset, like this `-Tv140`

1. __`CMAKE_BUILD_TYPE`__, specify the build mode, Debug or Release

    * `-DCMAKE_BUILD_TYPE=Release` to generate the Release mode project, the default build mode is Debug

1. __`-H -B`__, `-H` specify the CMake project Home directory, `-B` specify CMake-generated project binary directory. for example

    * `-H..\cocos2d-x -Bmsvc_build` the generated native project's location will be `msvc_build` directory.

1. __`--build  <dir>`__, build a CMake-generated project binary tree, for example

    * `cmake --build ./msvc_build`, cmake will sellect corresponding build tools.

### Cocos2d-x Options

1. __`GEN_COCOS_PREBUILT`__, control the project have the feature to generate pre-build libraries or not. Default value is `OFF`

    * `-DGEN_COCOS_PREBUILT=ON`, will add target prebuilt, build this target will generate prebuilt libraries

1. __`USE_COCOS_PREBUILT`__, control the project have the feature to use pre-build libraries or not. Default value is `OFF`

    * `-DUSE_COCOS_PREBUILT=ON`, will disable libraries target, and make app target use prebuilt libraries

1. __`COCOS_PREBUILT_ROOT`__, a path means the prebuilt libraries root location, it's not optional for Android Project on Android Studio, optional for other supported platforms. the default value is $cocos2dx_root/prebuilt if the cmake can access to cocos2d-x environment variable. for example

    * `arguments "-DCOCOS_PREBUILT_ROOT=/Users/laptop/cocos-prebuilt"` set this value on [cmake block](https://github.com/cocos2d/cocos2d-x/blob/84be684e3858393a6f3efc50e3f95d4e0ac92a20/tests/cpp-empty-test/proj.android/app/build.gradle#L31) of build.gradle file.

1. Any options in [SelectModule.cmake](./Modules/SelectModule.cmake) can be set manually. Do it if you know what you're doing.

## Useful Links

* CMake Official website: [cmake.org](https://cmake.org/)

* CMake Documentation: [cmake.org/documentation](https://cmake.org/documentation/)

* CMake FAQ: [Wiki/CMake_FAQ](https://cmake.org/Wiki/CMake_FAQ)