Libmypaint's Rust port

This is heavily in development. Only use this if you like bugs.

Why port libmypaint to Rust?

Why not? Honestly, it's not a great library. Mypaint suffers from it being too generic, and nothing else uses it (to my knowledge) because it's not generic enough. It being written in C means there's likely dozens of major bugs that haven't been discovered yet. In the end, libmypaint really needs a fresh start.

What are your goals?

• Step 1: Have a fully ABI-compatible libmypaint.so generated entirely in Rust with no C inter-op outside of FFI.
• Step 2: Clean this shit up. A direct port of C code to Rust does not look pretty.
• Step 3?: Possibly try and move some of the C++ in Mypaint to Rust. rust-cpython will help with this.
• Ultimate goal: Fully eliminate all unsafe code from Mypaint.

There's a few side goals as well, that I'm sure are manageable. For example, leveraging Rust's excellent concurrency tools to fully parallelize brush stroke painting would be pretty nice. Also a fully-featured test suite will make lives much easier.

So, where are you at now?

Around 70% ported. Got a few bugs that need hunting down, which is annoying because of the lack of testing beyond "open Mypaint and draw a bit". Most functions are ported over to equivalent Rust, and some areas that aren't publicly exposed have been cleaned up a lot. Progress is slow but steady, as I tend to be busy, so chances are if you find something broken, a PR would really help out.

Compiling and running

The current layout of the project is:

1. This crate is generating a .so
2. The .so is dynamically linked with C libmypaint's .so
3. Functions are removed from the C code, causing the linker to automatically use the Rust functions instead
4. Running Mypaint just involves telling it where our Rust-augmented libmypaint is

Steps:

1. Install Rust if you haven't already and run cargo build --release in this project.
2. Clone the libmypaint repo
3. Checkout f052590 (just in case changes make incompatibilities pop up, which is unlikely as libmypaint development is slow)
4. Follow libmypaint's compilation guide, but replace ./configure with ./configure LDFLAGS="-L/path/to/rustport/target/release/ -lrustport"
5. It should make properly without complaining. If it doesn't then uh, make an issue?
6. Clone Mypaint and follow its installation instructions.
7. Export LD_PRELOAD as /path/to/our/libmypaint/.libs/libmypaint.so and LD_LIBRARY_PATH as /path/to/rustport/target/release/
8. Run Mypaint and pray that it works.