readme: description, build instructions

README.md

@@ -1,17 +1,38 @@
-This is a minimal test application based on `GameActivity` that just
-runs a mainloop based on android_activity::poll_events() and traces
-the events received without doing any rendering. It also saves and
-restores some minimal application state.
+# Grim
+
+Cross-platform GUI for [Grin](https://github.com/mimblewimble/grin) on [Rust](https://stackoverflow.blog/2020/01/20/what-is-rust-and-why-is-it-so-popular/) with focus on usability and availability to be used by anyone, anywhere. Named by character [Grim](https://harrypotter.fandom.com/wiki/Grim) - giant, spectral dog that haunts churchyards.
+## Build instructions
+### Install Rust
+`curl https://sh.rustup.rs -sSf | sh`
+
+### Desktop
+
+To build and run application go to project directory and run:
 
 ```
-export ANDROID_NDK_HOME="path/to/ndk"
-export ANDROID_HOME="path/to/sdk"
-
-rustup target add aarch64-linux-android
-cargo install cargo-ndk
-
-export CPPFLAGS="-DMDB_USE_ROBUST=0" && export CFLAGS="-DMDB_USE_ROBUST=0" && cargo ndk -t arm64-v8a -o app/src/main/jniLibs/ build
-./gradlew build
-./gradlew installDebug
-adb shell am start -n mw.gri.android/.MainActivity
+cargo build release
+./target/release/grim
 ```
+
+### Android
+#### Set up the environment
+
+Install Android SDK / NDK / Platform Tools
+```
+brew cask install android-sdk android-ndk android-platform-tools
+```
+
+Add to your `.bashprofile` or `.zshrc`:
+```
+export ANDROID_HOME="$(brew --prefix)/share/android-sdk"
+export PATH=$PATH:$ANDROID_HOME/emulator:$ANDROID_HOME/tools:$ANDROID_HOME/tools/bin:$ANDROID_HOME/platform-tools
+export ANDROID_NDK_HOME="$(brew --prefix)/share/android-ndk"
+```
+
+#### Build the project
+Run Android emulator or connect a real device. Command `adb devices` should show at least one device.
+In the root of the repo run `./build_run_android.sh release {arch}`, where is `arch` is `v7` or `v8` based on device CPU architecture.
+
+## License
+
+Apache License v2.0.