• PreonEngine
  • Compatibility
    • Android
      • Setup
      • Code
      • Running
      • Debugging

PreonEngine

An extremely customizable, modular, fast, gpu-accelerated, cross-platform solution for creating user-interfaces minimal effort.

Compatibility

Platform	Status	Rendering Backend(s)
Windows 10+	✔️	DX12, Vulkan
Windows 8.1-	⚠️	Vulkan, experimental DX11
MacOS/iOS	✔️	Metal
Linux X11/Wayland	✔️	Vulkan, GLES3
Android	✔️	Vulkan, GLES3

Android

Setup

Download & install the recommended version of the Android NDK ("Current LTS Release", avoid the beta version).

Install cargo-apk:

cargo install cargo-apk

Setting up your device (pick one, real hardware is easier):

• Real hardware
  • Enable developer options and enable USB debugging
  • Connect your phone via USB cable to your pc
• Emulator (virtual phone):
  • Download & install the official Android emulator from google
  • Make sure everything is setup correctly with PATH variables etc.

Code

Recommended setup for single codebase applications supporting both mobile & desktop:

File structure (optional)

my_application
├──res
│   └──image.png
├──src
│   ├──app.rs
│   ├──main.rs
│   └──lib.rs
└──Cargo.toml

Cargo.toml

[features]
default = [] # 1
android = ["ndk-glue", "preon_module_wgpu/android"] # 2

[dependencies]
preon_engine = { path = "../preon_engine" }
ndk-glue = { version = "0.3.0", optional = true } # 3
preon_module_wgpu = { path = "../preon_module_wgpu" }

[lib]
crate-type = ["cdylib"] # 4

1. Don't enable any features by default
2. When the android feature is specified in cargo, it will enable the ndk-glue dependency and enable the android feature in preon_module_wgpu
3. Specify the ndk-glue dependency, but don't enable it by default. Warning: If you have a tool that checks for dependencies and their updates, ignore the update for ndk-glue, as winit depends on this specific version.
4. Android requires a dynamic library for native code.

main.rs

mod app;

// Desktop entry point
fn main() {
    app::app();
}

app.rs

pub fn app() {
    // Regular preon_engine code here
}

lib.rs

mod app;

// Mobile entry point
#[cfg_attr(target_os = "android", ndk_glue::main(backtrace = "on"))]
pub fn main() {
    app::app();
}

Why so weird?

Android needs native code to be a dynamically linked library, so you simply cant use fn main(). And while we can very easily use the official example to narrow it down to only 2 files, I've found that it can sometimes break IDE & rust-analyzer functionality due to the macro. This solution avoids that.

Running

To run your app on android you would run:

cargo apk run --features android

Running on desktop remains the same:

cargo run

Debugging

To view stdout (println!, panic!, etc.), run (with your phone connected of course):

adb logcat RustStdoutStderr:D *:S