Added a Vello back-end with a custom winit viewer.

My first PR! 🎉

You can get Rust with [Rustup](https://rustup.rs). Then run `cargo run --release` in the `vello/` directory.

Things left to do before merging:
- [x] remove `clap`
- [x] add rustfmt & clippy checks to CI
- [x] add text support
- [x] add README
- [ ] add CONTRIBUTING

Diffs=
abe5aab14 Added a Vello back-end with a custom winit viewer. (#5786)

Co-authored-by: Dragoș Tiselice <[email protected]>
Co-authored-by: Dragoș Tiselice <[email protected]>

.rive_head

@@ -1 +1 @@
-adeebb26a7ac58a1aaa18a40ed9d98af46735c97
+abe5aab1431c34a42458a9650831d6b3a7c39feb

vello/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "rive-vello"
+version = "0.1.0"
+edition = "2021"
+
+[build-dependencies]
+cc = { version = "1.0", features = ["parallel"] }
+walkdir = "2.3.3"
+
+[dependencies]
+clap = { version = "4.3.19", features = ["derive"] }
+image = "0.24.6"
+pollster = "0.3.0"
+smallvec = "1.8.0"
+vello = { git = "https://github.com/linebender/vello", rev = "3cb5462" }
+wgpu = "0.17.0"
+winit = "0.28.6"

vello/README.md

@@ -0,0 +1,31 @@
+# Vello back-end for Rive
+
+Small application for viewing `.riv` files rendered with Vello. It uses [winit]
+for creating the window and [image] to decode images.
+
+## Build
+
+You will need clang, Cargo, and the Rust compiler to build. You can can install
+Cargo and rustc using [rustup].
+
+To use the application, run:
+
+```bash
+$ cargo run --release
+```
+
+## Usage
+
+Drop any `.riv` file into the window to open it. Scroll to control the size of
+the grid of copies.
+
+## Caveats
+
+The current implementation is a work-in-progress and might exhibit artifacts or
+render incorrectly.
+
+Only tested on macOS for the time being.
+
+[winit]: https://github.com/rust-windowing/winit
+[image]: https://github.com/image-rs/image
+[rustup]: https://rustup.rs

vello/build.rs

@@ -0,0 +1,118 @@
+use std::{
+    env,
+    ffi::OsString,
+    path::{Path, PathBuf},
+    process::Command,
+};
+
+use walkdir::WalkDir;
+
+const CHECKOUT_DIRECTORY: &str = "target";
+
+struct Checkout {
+    path: PathBuf,
+}
+
+impl Checkout {
+    pub fn new(repo: &str, tag: &str) -> Self {
+        let name = repo.rsplit_once('/').expect("URL format invalid").1;
+        let mut path = PathBuf::from(CHECKOUT_DIRECTORY);
+
+        path.push(name);
+
+        if !path.is_dir() {
+            Command::new("git")
+                .args([
+                    "clone",
+                    "-b",
+                    tag,
+                    repo,
+                    &path.as_os_str().to_string_lossy(),
+                ])
+                .output()
+                .unwrap_or_else(|_| panic!("failed to clone {}; is git CLI available?", name));
+        }
+
+        Self { path }
+    }
+
+    pub fn join<P: AsRef<Path>>(&self, path: P) -> PathBuf {
+        self.path.join(path)
+    }
+}
+
+fn all_files_with_extension<P: AsRef<Path>>(
+    path: P,
+    extension: &str,
+) -> impl Iterator<Item = PathBuf> + '_ {
+    WalkDir::new(path).into_iter().filter_map(move |entry| {
+        entry
+            .ok()
+            .map(|entry| entry.into_path())
+            .filter(|path| path.extension() == Some(&OsString::from(extension)))
+    })
+}
+
+fn main() {
+    println!("cargo:rerun-if-changed=src/vello_renderer.hpp");
+    println!("cargo:rerun-if-changed=src/vello_renderer.cpp");
+    println!("cargo:rerun-if-changed=src/winit_viewer.cpp");
+
+    let harfbuzz = Checkout::new("https://github.com/harfbuzz/harfbuzz", "8.1.1");
+    let sheen_bidi = Checkout::new("https://github.com/Tehreer/SheenBidi", "v2.6");
+
+    let target = env::var("TARGET").unwrap();
+    let profile = env::var("PROFILE").unwrap();
+
+    let mut cfg = cc::Build::new();
+    cfg.compiler("clang")
+        .cpp(true)
+        .flag_if_supported("-std=c++11") // for unix
+        .warnings(false)
+        .file(harfbuzz.join("src/harfbuzz.cc"));
+
+    if !target.contains("windows") {
+        cfg.define("HAVE_PTHREAD", "1");
+    }
+
+    if target.contains("apple") && profile.contains("release") {
+        cfg.define("HAVE_CORETEXT", "1");
+    }
+
+    if target.contains("windows") {
+        cfg.define("HAVE_DIRECTWRITE", "1");
+    }
+
+    if target.contains("windows-gnu") {
+        cfg.flag("-Wa,-mbig-obj");
+    }
+
+    cfg.compile("harfbuzz");
+
+    cc::Build::new()
+        .compiler("clang")
+        .files(all_files_with_extension(sheen_bidi.join("Source"), "c"))
+        .include(sheen_bidi.join("Headers"))
+        .compile("sheenbidi");
+
+    cc::Build::new()
+        .compiler("clang")
+        .cpp(true)
+        .files(all_files_with_extension("../src", "cpp"))
+        .files(all_files_with_extension(
+            "../viewer/src/viewer_content",
+            "cpp",
+        ))
+        .file("src/vello_renderer.cpp")
+        .file("src/winit_viewer.cpp")
+        .include("src")
+        .include("../include")
+        .include("../viewer/include")
+        .include(harfbuzz.join("src"))
+        .include(sheen_bidi.join("Headers"))
+        .flag("-std=c++14")
+        .flag("-Wno-everything")
+        .define("RIVE_SKIP_IMGUI", None)
+        .define("WITH_RIVE_TEXT", None)
+        .compile("rive");
+}