Added document how to build Yoga for Java

java/BUILD_JAVA.md

@@ -0,0 +1,99 @@
+## Building Yoga native lib for Java
+Instruction how to build Yoga native lib on local MacOs/Linux machine.
+
+### Prerequisites
+Required tools:
+* ninja
+* cmake
+* g++
+
+### Steps
+
+1. Modify `cmake/project-defaults.cmake` file by commenting out `-Werror`:
+
+    ```diff
+    diff --git a/cmake/project-defaults.cmake b/cmake/project-defaults.cmake
+    index 987529c..c28d542 100644
+    --- a/cmake/project-defaults.cmake
+    +++ b/cmake/project-defaults.cmake
+    @@ -33,7 +33,7 @@ add_compile_options(
+         -fexceptions
+         # Enable warnings and warnings as errors
+         -Wall
+    -    -Werror
+    +    #-Werror
+         # Disable RTTI
+         $<$<COMPILE_LANGUAGE:CXX>:-fno-rtti>
+         # Use -O2 (prioritize speed)
+    ```
+2. Modify `java/CMakeLists.txt` file:
+
+    ```diff
+    diff --git a/java/CMakeLists.txt b/java/CMakeLists.txt
+    index d8afd67..185a6fb 100644
+    --- a/java/CMakeLists.txt
+    +++ b/java/CMakeLists.txt
+    @@ -5,8 +5,13 @@
+
+     cmake_minimum_required(VERSION 3.13...3.26)
+     project(yogajni)
+    +find_package(JNI REQUIRED)
+    +include_directories(${JNI_INCLUDE_DIRS})
+     set(CMAKE_VERBOSE_MAKEFILE on)
+
+    +set(CMAKE_CURRENT_SOURCE_DIR ${CMAKE_SOURCE_DIR})
+    +message(CMAKE_CURRENT_SOURCE_DIR="${CMAKE_CURRENT_SOURCE_DIR}")
+    +
+     set(YOGA_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/..)
+     include(${YOGA_ROOT}/cmake/project-defaults.cmake)
+
+    @@ -18,5 +23,9 @@ file(GLOB VERSION_SCRIPT CONFIGURE_DEPENDS
+         ${CMAKE_CURRENT_SOURCE_DIR}/yogajni.version)
+
+     add_library(yoga SHARED ${SOURCES})
+    +
+    +# TODO export lib with .so extension on MacOS with Apple Silicon
+    +#set_target_properties(yoga PROPERTIES SUFFIX ".so")
+    +
+     target_link_libraries(yoga yogacore)
+    -target_link_options(yoga PRIVATE -Wl,--version-script=${VERSION_SCRIPT})
+    +target_link_options(yoga PRIVATE "-Wl")
+    ```
+
+3. Create a `./build_java` build file.
+
+    ```bash
+    #!/bin/sh
+    # Copyright (c) Meta Platforms, Inc. and affiliates.
+    #
+    # This source code is licensed under the MIT license found in the
+    # LICENSE file in the root directory of this source tree.
+
+    cd "$(dirname "$0")/java"
+    rm -rf build
+
+    if [ "$#" -eq 0 ]; then
+      build_type="Debug"
+    else
+      build_type="$1"
+    fi
+
+    if which ninja; then
+      set -e
+      cmake -B build -S . -D CMAKE_OSX_ARCHITECTURES=arm64 -D CMAKE_BUILD_TYPE="$build_type" -G Ninja
+    else
+      set -e
+      cmake -B build -S . -D CMAKE_BUILD_TYPE="$build_type"
+    fi
+
+    cmake --build build
+
+    find . \( -name "*.so" -o -name "*.dylib" \)
+
+    ```
+4. Run `./build_java` from the terminal.
+
+    MacOS systems will create a `.dylib`, whereas Linux an `.so` version of the library. 
+    There's possiblity to build yoga lib for two architectures (only for MacOs), just update `CMAKE_OSX_ARCHITECTURES` flag to: `CMAKE_OSX_ARCHITECTURES:STRING="x86_64;arm64"`.
+
+6. Artifact location will be printed in output. Output may contain several warnings - which are a non-issue. If there's a library location printed out at the end, the build was successful.