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godmodelabs / ejecta-v8

A port of @phoboslabs EjectaJS which uses v8 instead of JavaScriptCore.
http://godmodelabs.github.io/ejecta-v8/
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About

This library ports the excellent EjectaJS (https://github.com/phoboslab/Ejecta) to Android, replacing JavascriptCore with v8 in the process. Think of it as a Javascript engine with Canvas and AJAX but no DOM. If you want fast rendering of a cross-platform Canvas-based JS application this is for - if you have a web application or your JS code accesses the DOM in any way a WebView will be a better choice.

Ejecta-v8 is published under the MIT Open Source License (http://opensource.org/licenses/mit-license.php), as is Ejecta.

You can use our sample app under https://github.com/godmodelabs/ejecta-v8-sample to get a feel for the library.

This library needs a precompiled, statically linked version of v8 to link against. Currently this is tested against 8.2.297.3 See also Updating v8.

It also needs a precompiled, statically linked version of libuv.

Getting v8 & uv libraries

Precompiled from DropBox

  1. Download the precompiled libs from DropBox
  2. Unpack into libs/

The libs/v8 folder should look like this:

# pwd
~/git/ejecta-v8/libs/v8
# ls
arm64-v8a   armeabi-v7a x86         x86_64

The folders in livs/uv should be the same.

Building libuv from sources

Coming soon.

Important notes:

  1. Use 64 bit linux, was used ubuntu-18.04.3-live-server-amd64.iso, sudo apt-get -y install git cmake python unzip pkg-config clang-8 wget
  2. Do not configure & compile using root
  3. Do not configure & compile using script
  4. Do not use d8, custom libc++, manual linking(std namespace must use stable, static ABI, i.e. ::__ndk:: internal namespace. NOT a ::__:: or ::__1:: or ::__Cr::).
  5. Make sure to add/use extra args when configuring & compiling to same host_cpu and target_cpu, in this example it's x64

Building v8 from sources

We need NDK r20b. We assume it to be in $NDKPATH:

export ANDROID_NDK_HOME=~/android-ndk-r20b (or wherever you installed it to). Don't forget to add it to the path: export PATH=$PATH:$ANDROID_NDK_HOME

For steps 1 and 2 see also the v8 project documentation.

  1. get depot_tools
  2. Get the sources: fetch v8
  3. cd v8
  4. Checkout correct revision: git checkout 8.2.297.3
  5. echo "target_os = ['android']" >> ../.gclient && gclient sync --nohooks as described on v8 wiki
  6. Create GN build configuration for each ABI.

    x64

    gn gen out.gn/x64.release --args='host_cpu="x64" is_clang=true is_component_build=false is_debug=false is_official_build=true strip_debug_info=true symbol_level=0 target_cpu="x64" target_os="android" treat_warnings_as_errors=false v8_enable_i18n_support=false v8_enable_verify_heap=true v8_target_cpu="x64" v8_use_external_startup_data=false use_thin_lto=false use_glib=false android_ndk_root="${ANDROID_NDK_HOME}" libcxx_abi_unstable=false use_sysroot=false use_custom_libcxx=false v8_static_library=true v8_monolithic=true' ninja -C out.gn/x64.release v8_monolith

    arm

    gn gen out.gn/arm.release --args='host_cpu="x64" is_clang=true is_component_build=false is_debug=false is_official_build=true strip_debug_info=true symbol_level=0 target_cpu="arm" target_os="android" treat_warnings_as_errors=false v8_enable_i18n_support=false v8_enable_verify_heap=true v8_target_cpu="arm" v8_use_external_startup_data=false use_thin_lto=false use_glib=false android_ndk_root="${ANDROID_NDK_HOME}" use_custom_libcxx=false v8_static_library=true v8_monolithic=true' ninja -C out.gn/arm.release v8_monolith

    arm64

    gn gen out.gn/arm64.release --args='host_cpu="x64" is_clang=true is_component_build=false is_debug=false is_official_build=true strip_debug_info=true symbol_level=0 target_cpu="arm64" target_os="android" treat_warnings_as_errors=false v8_enable_i18n_support=false v8_enable_verify_heap=true v8_target_cpu="arm64" v8_use_external_startup_data=false use_thin_lto=false use_glib=false android_ndk_root="${ANDROID_NDK_HOME}" use_custom_libcxx=false v8_static_library=true v8_monolithic=true' ninja -C out.gn/arm64.release v8_monolith

    x86

    gn gen out.gn/x86.release --args='host_cpu="x64" is_clang=true is_component_build=false is_debug=false is_official_build=true strip_debug_info=true symbol_level=0 target_cpu="x86" target_os="android" treat_warnings_as_errors=false v8_enable_i18n_support=false v8_enable_verify_heap=true v8_target_cpu="x86" v8_use_external_startup_data=false use_thin_lto=false use_glib=false android_ndk_root="${ANDROID_NDK_HOME}" use_custom_libcxx=false v8_static_library=true v8_monolithic=true' ninja -C out.gn/x86.release v8_monolith

  7. Copy and rename resulting libv8_monolith.a into the folder where ndk-build expects it: cp libv8_monolith.a $PATH_TO_YOUR_EJECTAV8_CHECKOUT/bgjslibrary/jni/libs/$ABI/libv8.a where $ABI is either armeabi-v7a, arm64-v8a, x86 or x86_64.

Steps 6-7 can be repeated as mentioned for each ABI you want to support. Step 7 can set is_debug to false of course.

Building the sample

Set up at least NDK r20b and make sure it is in the search path.

./gradlew assembleDebug

Updating v8

Find good v8 version: Gist that explains it. See the list of v8 release information

ARMv7 NEON

I opted to compile the arm version with support for NEON instructions, as non-NEON devices are becoming very rare. Make sure to either compile without this option if supporting Tegra 2 is important to you, or disable these devices in the Play Store: List of non-neon devices