GDExtension loading file generation for Rust

This crate aims to provide a way to autogenerate a .gdextension file for using Rust to make a Godot GDExtension. It provides all the libraries pathfinding and a way to automatically link the default icons to the new defined classes based on the class they inherit from, and also a way to manually link a specific class with a custom icon. For more information, read the documentation, or the source code.

Installation

To install this crate as a build dependency in your own crate, run: cargo add --build gdext-gen. If you instead want it added as a normal dependency run: cargo add gdext-gen.

Usage

build.rs call

To get all the functionality of this crate, in your build.rs file on the root of your crate (not your src/), write the following (parameters may vary depending on the features you've opt in or out of):

use gdext_gen::generate_gdextension_file;

fn main() {
    // All your variable initialization and setup goes here.
    generate_gdextension_file(base_dir, target_dir, gdextension_path, force_generation, configuration, windows_abi, icons_configuration, dependencies);
}

The parameters of this function and how it works are documented in the docs. It should be kept in mind that this function returns an std::io::Result, so the following code could be used instead:

use std::io::Result;
use gdext_gen::generate_gdextension_file;

fn main() -> Result<()> {
    // All your variable initialization and setup goes here.
    generate_gdextension_file(base_dir, target_dir, gdextension_path, force_generation, configuration, windows_abi, icons_configuration, dependencies)?;
}

To compile for Android, Web, MacOS or iOS please refer to the godot-rust book.

It's worth noting that one can configure when the build script will be run, so it's sensible to change it were one not to need it running at every source file change.

Variable initialization

An example of variable initialization to have parity with the godot-rust example is the following (with all the primaty features enabled and checked_generation chosen):

fn main() -> Result<()> {
    generate_gdextension_file(
        BaseDirectory::ProjectFolder.into(),
        Some("../rust/target".into()),
        Some("../godot/rust.gdextension".into()),
        true,
        Some(Configuration::new(
            EntrySymbol::GodotRustDefault,
            Some((4, 1)),
            None,
            true,
            false,
        )),
        Some(WindowsABI::MSVC),
        Some(IconsConfig::new(
            DefaultNodeIcon::NodeRust(NodeRust::Ferris, "rust".into()),
            IconsCopyStrategy::new(true, true, "../godot/addons/rust".into(), false),
            None,
            IconsDirectories::new("addons".into(), "editor".into(), "rust".into(), BaseDirectory::ProjectFolder.into()),
        )),
        None,
    )?;

    Ok(())
}

This results in a "rust.gdextension" file in "Project/godot", which contains the following:

[configuration]
entry_symbol = "gdext_rust_init"
compatibility_minimum = 4.1
reloadable = true

[libraries]
"target.mode" = "res://../rust/target/mode/library.file"
"target.mode.architecture" = "res://../rust/target/target-triple/mode/library.file"
...

[icons]
YourStructName = "res://addons/rust/NodeRust.svg"
...

Few lines of code for a customized automated .gdextension file, in conclusion.

Variables short explanation

Based on the last example, the GDExtension is configured as follows:

• BaseDirectory::ProjectFolder uses "res://" based paths.
• target_dir = "../rust/target": The target folder for the GDExtension crate is found at "res://../rust/target".
• gdextension_path = "../godot/rust.gdextension: Makes the file at "Project/godot/rust.gdextension" (if "rust" and "godot" are in a "Project" folder).
• true here means the .gdextension will be rewritten even if the file already exists.
• EntrySymbol::GodotRustDefault defaults to "gdext_rust_init".
• minimum_compatibility -> 4.1 and reloatable = true
• WindowsABI::MSVC uses MSVC as linker and environment when compiling for Windows.
• DefaultNodeIcon::NodeRust(NodeRust::Ferris, "rust") uses the NodeRustFerris.svg icon and finds it in the folder "res://{base_dir}/rust".
• IconsCopyStrategy: true, copy the NodeRust (and true) files in path "../godot/addons/rust" relative to your crate and if it's there, don't copy it again.
• No custom nodes.
• The directories will be laid out as following:
  • All icons will be found relative to "res://addons".
  • The editor icons will be located in "res://addons/editor".
  • The custom nodes will be located in "res://addons/rust"
• None: No dependencies.

Features

• icons - Allows the use of custom icons and the copying of Rust's default icons for the generation of the icons section of the .gdextension file.
• find_icons - Allows for the finding of the names of the custom implemented nodes and their subclasses using regex to automate the icons section generation process.
• dependencies - Allows for the generation of the dependencies section of the .gdextension file.
• checked_generation - Adds a parameter to the function call to allow for specifying whether the .gdextension file should always be copied or only when it doesn't exist. This option is mutually exclusive with forced_generation. If none is chosen, it defaults to writing it only when it doesn't exist.
• forced_generation - Ensures the .gdextension file is always written regardless of whether it exists or not. This option is mutually exclusive with checked_generation. If none is chosen, it defaults to writing it only when it doesn't exist.

Limitations

The feature "find_icons" uses regex to do its work. It's not a perfect way of finding the icons for each GDExtension custom node, but it always resets after each file, so one file's contents failing can only affect itself. It does so by searching for lines that contain both "base" and "=", then trying to find the name of the base. Same with "struct". The only ways it could fail is if that exact appearance is in a comment or string, has comments in between or extends over more than a line. I believe these to be reasonable compromises, as searching for more than these would only make the code slower, and any reasonably formatted code would have "base =" in the same line and for "base = NameBase", or struct "NameStruct {" to appear on their own in a comment is hard enough, and the auto found icons can ALWAYS be overriden by custom icons that just happen to be the editor's. In any case, if one thinks otherwise, here are other ways to implement this. 1: A pretty barebones Rust parser, 2: Preprocessing strings and comments in a file before doing the search, 3: Searching for the impl INameOfBase for StructName. If you experience problems due to this fact, due let us know, there may be a fix for it.

There is also an issue with structs that use generics, or structs that don't follow the standard. These, may not be found at all, so it's best to just add them as custom.

Acknowledgements

• This crate is based on the gdextension_file documentation from Godot, and some snippets of the documentation (all written by paddy-exe) are taken as are from their documentation, so they are as accurate as possible. The copyright notices for those files can be found directly in their repository, and are licensed under the CC BY 3.0 license. This applies to the doc comments on the serializable structs, so these are not relicensed under the licenses of this repository. The schema for the .gdextension file comes from the Godot Engine which is licensed under the MIT license.
• This crate is meant to work in tandem with godot-rust to give the most painless use of Rust for Godot's GDExtension, automating a helpful bunch of the work. It could be use on its own, just to generate the .gdextension file, but it works best with it.
• The explanation on the WindowsABI::LLVM documentation, taken from the rustc documentation, which is licensed under the MIT license.

Asset licenses

• The default GDExt Rust node's icons, NodeRustSmall.svg, NodeRustLarge.svg and NodeRustFerris.svg are licensed under the CC BY 4.0 license, copyright by burritobandit28, so they is not relicensed under the licenses of this repository. They are derived from the following works:

• Rust Ferris, made by Karen Rustad Tölva and licensed under the CC0 1.0 Universal license.

• Ferris emoji, made by Dzuk and licensed under the CC BY-NC-SA 4.0 license.

• Godot logo, made by Andrea Calabró and licensed under the CC BY 4.0 license.

• godot-rust Ferris, licensed under the CC BY-NC-SA 4.0 license, from godot-rust.