Merge pull request #158 from garanj/watchface-libs-example

Adds example of building Pack

Author: garanj

watchface/README.md

@@ -20,5 +20,25 @@ example, using `pngquant` on all images, to help keep the watch face size to a m
 ## Packaging the watch face
 
 To package the watch face, the [Pack](https://github.com/google/pack) is used. This is a native
-library, so the pre-builts are provided in `jniLibs`. A script is also included for building these
-fresh, but that should not be necessary.
+library, so the pre-builts are provided in `jniLibs`.
+
+## Building native libraries
+
+A script is also included for building these fresh, but that is generally not necessary when
+building Androidify.
+
+However, if you do wish to build these, follow these steps in order to run the script:
+
+1. [Install][install-ndk] the Android NDK.
+2. [Install][install-rust] Rust and Cargo.
+3. Make a copy of `watchface/pack-java/.cargo-example` as
+    `watchface/pack-java/.cargo`.
+4. Open `watchface/pack-java/.cargo/config.toml`.
+5. Adjust all the `linker` and `ar` paths, replacing `<NDK_PATH>` with the absolute path to your
+   Android NDK installation. Note that each linker must support API level 26 and above, to match
+   the Androidify `minSdk`. For example: `armv7a-linux-androideabi26-clang`.
+6. Execute the `watchface/provide-libraries-to-androidify-project.sh` script. This will build the native
+   libraries and copy them to the `jniLibs` directory.
+
+[install-ndk]: https://developer.android.com/studio/projects/install-ndk#default-version
+[install-rust]: https://rust-lang.org/tools/install/

watchface/pack-java/.cargo-example/config.toml

@@ -0,0 +1,20 @@
+# The paths below are examples for a macOS (darwin-x86_64) host.
+# You will need to adjust them for your operating system and NDK installation.
+# Replace <NDK_PATH> with the absolute path to your Android NDK installation.
+
+# Real watch
+[target.armv7-linux-androideabi]
+linker = "<NDK_PATH>/toolchains/llvm/prebuilt/darwin-x86_64/bin/armv7a-linux-androideabi26-clang"
+ar = "<NDK_PATH>/toolchains/llvm/prebuilt/darwin-x86_64/bin/llvm-ar"
+# Emulator
+[target.i686-linux-android]
+linker = "<NDK_PATH>/toolchains/llvm/prebuilt/darwin-x86_64/bin/i686-linux-android26-clang"
+ar = "<NDK_PATH>/toolchains/llvm/prebuilt/darwin-x86_64/bin/llvm-ar"
+# Emulator on Apple Silicon MacBooks
+[target.aarch64-linux-android]
+linker = "<NDK_PATH>/toolchains/llvm/prebuilt/darwin-x86_64/bin/aarch64-linux-android26-clang"
+ar = "<NDK_PATH>/toolchains/llvm/prebuilt/darwin-x86_64/bin/llvm-ar"
+# Emulator (64-bit x86_64)
+[target.x86_64-linux-android]
+linker = "<NDK_PATH>/toolchains/llvm/prebuilt/darwin-x86_64/bin/x86_64-linux-android26-clang"
+ar = "<NDK_PATH>/toolchains/llvm/prebuilt/darwin-x86_64/bin/llvm-ar"