Cross-Platform

Platform Strategy

Every target is built from the same jengine-core crate:

Target	Runtime	Rendering	Audio	Scripting
Windows	`jengine-runtime` (winit + wgpu)	DX12 / Vulkan	kira (cpal)	Luau (`mlua`) + JavaScript (`rquickjs`)
Android	`jengine-runtime` as a NativeActivity APK	Vulkan, GLES fallback	kira	Luau only
Web	`jengine-web` (wasm-bindgen)	WebGPU, WebGL2 fallback	Web Audio API	Fengari (Lua 5.3)
Editor	`jengine-editor-viewport` inside Tauri	WebGPU in WebView2	Web Audio API	Fengari — the same bundle as web builds

So what you verify in the editor is what a web build runs, while native runs Luau. Keep scripts to the common subset of the two Lua dialects, standard library included.

A project with its own Rust packages gets a generated crate per target — <project>/.jengine/runtime/, /web/ and /viewport/ — that links them in.

Feature Gating

Platform-specific code uses cfg attributes (#[cfg(target_arch = "wasm32")], #[cfg(target_os = "android")]) and Cargo features. jengine-core’s features:

Feature	Brings
`native` (default)	`mlua` (Luau)
`physics` (default)	`rapier2d`
`audio` (default)	`kira`
`js-adapter-host`	`rquickjs`, for JavaScript and batch scripts on the desktop
`web`	`wasm-bindgen`, `web-sys`, `js-sys`
`gpu-wgpu`	the wgpu renderer
`backend-dx12`, `backend-vulkan`, `backend-metal`, `backend-webgpu`, `backend-webgl`	one wgpu backend each

cargo check -p jengine-core without gpu-wgpu does not compile the renderer; check renderer changes with --features gpu-wgpu, or against the editor’s real target with cargo check -p jengine-editor-viewport --target wasm32-unknown-unknown. Android-only code is checked with cargo ndk -t arm64-v8a check -p jengine-runtime.

Shaders

Shaders are WGSL, one source for every backend. They live in crates/jengine-core/assets/shaders/wgsl/ and are embedded at compile time with include_str!(); wgpu translates them to whatever the chosen backend speaks. Shader graphs generate WGSL too.

Avoid WGSL’s bit functions (firstTrailingBit and kin) in a shader the lights or sprites use: naga writes them as GLSL ES 3.10 calls that WebGL2 cannot compile.

Which backends a build carries is a project setting (Project Settings → Graphics). A crate that enables jengine-core/gpu-wgpu must name at least one backend feature or it compiles with no backend and fails at adapter request at runtime.

Key Gotchas

image crate: must use default-features = false on WASM (rayon breaks single-threaded WASM)
WebGPU canvases offer no sRGB format: the browser hosts draw through an sRGB view of the canvas, so colours match native
winit 0.30: windows are created inside the event loop (the Resumed handler), not before
glam SIMD: enabled on WASM via .cargo/config.toml with -C target-feature=+simd128
Batch scripts run on the native desktop runtime only
A web page served over https cannot open a plain ws:// socket to the online relay