nix: prepare targets with rust-overlay

pre-install the system-images
add doc of using avd without android-studio

README.md

@@ -60,11 +60,23 @@ $ cargo apk run --release
 
 ## Android Emulator
 
+With Android Studio:
+
 - Install [Android Studio](https://developer.android.com/studio)
 - Open 'Device Manager' in Android Studio
 - Add a new device with API level `34` and ABI `arm64-v8a` (even though the app uses 30, the 30 emulator can't find the vulkan adapter, but 34 works fine)
 - Start up the emulator
 
+Without Android Studio:
+
+```sh
+# create emulator
+avdmanager create avd -k 'system-images;android-34;google_apis;arm64-v8a' -n notedeck
+
+# start up the emulator
+env ANDROID_EMULATOR_WAIT_TIME_BEFORE_KILL=999 emulator -avd notedeck
+```
+
 while the emulator is running, run:
 
 ```bash

shell.nix

@@ -1,20 +1,46 @@
-{ pkgs ? import <nixpkgs> { }
-, android ? "https://github.com/tadfisher/android-nixpkgs/archive/refs/tags/2024-04-02.tar.gz"
+{ android ? "https://github.com/tadfisher/android-nixpkgs/archive/refs/tags/2024-04-02.tar.gz"
 , use_android ? true
 , android_emulator ? false
 }:
-with pkgs;
+with import <nixpkgs>
+{
+  overlays = [
+    (import (builtins.fetchTarball {
+      url = "https://github.com/oxalica/rust-overlay/archive/master.tar.gz";
+    }))
+  ];
+  config = {
+    android_sdk.accept_license = use_android;
+    allowUnfree = use_android;
+  };
+};
 
 let
   x11libs = lib.makeLibraryPath [ xorg.libX11 xorg.libXcursor xorg.libXrandr xorg.libXi libglvnd vulkan-loader vulkan-validation-layers libxkbcommon ];
+  rustc = (rust-bin.fromRustupToolchainFile ./rust-toolchain).override {
+    targets = [ ] ++
+      (lib.optionals (stdenv.isLinux && use_android) [
+        "aarch64-linux-android"
+      ]) ++
+      (lib.optionals (stdenv.isLinux && stdenv.isx86_64 && use_android && android_emulator) [
+        "x86_64-linux-android"
+      ]) ++
+      (lib.optionals (stdenv.isLinux && stdenv.isx86_64) [
+        "x86_64-unknown-linux-gnu"
+      ]) ++
+      (lib.optionals stdenv.isDarwin [
+        # TODO
+      ]);
+  };
 in
 mkShell ({
   nativeBuildInputs = [
+    rustc
     #cargo-udeps
     #cargo-edit
     #cargo-watch
-    rustup
-    rustfmt
+    # rustup
+    # rustfmt
     libiconv
     pkg-config
     #cmake
@@ -45,13 +71,17 @@ mkShell ({
       android-nixpkgs = callPackage (fetchTarball android) { };
       ndk-version = "24.0.8215888";
 
-      android-sdk = android-nixpkgs.sdk (sdkPkgs: with sdkPkgs; [
-        cmdline-tools-latest
-        build-tools-34-0-0
-        platform-tools
-        platforms-android-30
-        ndk-24-0-8215888
-      ] ++ lib.optional android_emulator [ emulator ]);
+      android-sdk = android-nixpkgs.sdk
+        (sdkPkgs: with sdkPkgs; [
+          cmdline-tools-latest
+          build-tools-34-0-0
+          platform-tools
+          platforms-android-30
+          ndk-24-0-8215888
+        ] ++
+        (lib.optionals android_emulator [ emulator ]) ++
+        (lib.optionals (android_emulator && stdenv.isx86_64) [ system-images-android-34-google-apis-x86-64 ]) ++
+        (lib.optionals (android_emulator && !stdenv.isx86_64) [ system-images-android-34-google-apis-arm64-v8a ]));
 
       android-sdk-path = "${android-sdk.out}/share/android-sdk";
       android-ndk-path = "${android-sdk-path}/ndk/${ndk-version}";