Dexterous Developer

An experimental hot reload system for the bevy game engine. Inspired by DGriffin91's Ridiculous bevy hot reloading, it aims to resolve two particular problems I had with it: the ability to re-load arbitrary systems, and then ability to transform resource/component structures over time.

Features

• Define the reloadable areas of your game explicitly - which can include systems, components and resources (w/ some limitations)
• Reset resources to a default or pre-determined value upon reload
• serialize/deserialize your reloadable resources & components, allowing you to evolve their schemas so long as they are compatible with the de-serializer (using rmp_serde)
• mark entities to get removed on hot reload
• run systems after hot-reload
• create functions to set-up & tear down upon either entering/exiting a state or on hot reload
• default to bypassing hot reload - only add the costs of hot reload during development, using the "hot" feature

Known issues

• Won't work on mobile or WASM, and only tested on Windows
• events and states still need to be pre-defined
• can't guarantee the main bevy thread will run on the main thread from an OS perspective, which can cause issues in some packages
  • Relies on a fork of bevy_winit (only when hot reload is enabled, will use the regular bevy_winit otherwise). A PR for adding the required ability to bevy exists.

Installation

In your Cargo.toml add the following:

[features]

hot = ["dexterous_developer_example/hot", "bevy/dynamic_linking"]



[lib]

name = "lib_THE_NAME_OF_YOUR_GAME"

path = "src/lib.rs"

crate-type = ["rlib", "dylib"]



[dependencies]

bevy = "0.11"

dexterous_developer_example = "0.0.1"

serde = "1" # If you want the serialization capacities

If your game is not a library yet, move all your main logic to lib.rs rather than main.rs. Then, in your main.rs:

fn main() {
    lib_THE_NAME_OF_YOUR_GAME::bevy_main(dexterous_developer::HotReloadOptions::default());
}

and in your lib.rs, your main function should become:

#[hot_bevy_main]
pub fn bevy_main(initial: InitialPlugins) {
    App::new().add_plugins(initial.with_default_plugins()) // This should replace the "DefaultPlugins", and you can use ".set()" on these as well. Use "with_minimal_plugins()" if you don't want the defaults.
    // ... and so on
}

If you have a plugin where you want to add reloadable elements, add the following in the file defining the plugin:

impl Plugin for MyPlugin {
    fn build(&self, app: &mut App) {
        app
            .setup_reloadable_elements::<reloadable>();
    }
}

#[dexterous_developer_setup]
fn reloadable(app: &mut ReloadableAppContents) {
    app
        .add_systems(Update, this_system_will_reload);
}

You might also want the following in your .cargo/config.toml:

# Add the contents of this file to `config.toml` to enable "fast build" configuration. Please read the notes below.



# NOTE: For maximum performance, build using a nightly compiler

# If you are using rust stable, remove the "-Zshare-generics=y" below.



[target.x86_64-unknown-linux-gnu]

linker = "clang"

rustflags = ["-Clink-arg=-fuse-ld=lld", "-Zshare-generics=y"]



# NOTE: you must install [Mach-O LLD Port](https://lld.llvm.org/MachO/index.html) on mac. you can easily do this by installing llvm which includes lld with the "brew" package manager:

# `brew install llvm`

[target.x86_64-apple-darwin]

rustflags = [

    "-C",

    "link-arg=-fuse-ld=/usr/local/opt/llvm/bin/ld64.lld",

    "-Zshare-generics=y",

]



[target.aarch64-apple-darwin]

rustflags = [

    "-C",

    "link-arg=-fuse-ld=/opt/homebrew/opt/llvm/bin/ld64.lld",

    "-Zshare-generics=y",

]



[target.x86_64-pc-windows-msvc]

linker = "rust-lld.exe"

rustflags = ["-Zshare-generics=n"]



# Optional: Uncommenting the following improves compile times, but reduces the amount of debug info to 'line number tables only'

# In most cases the gains are negligible, but if you are on macos and have slow compile times you should see significant gains.

#[profile.dev]

#debug = 1



# Enable a small amount of optimization in debug mode

[profile.dev]

opt-level = 1



# Enable high optimizations for dependencies (incl. Bevy), but not for our code:

[profile.dev.package."*"]

opt-level = 3



[profile.dev.package.gfx-backend-vulkan]

opt-level = 3

debug-assertions = false