Extremely basic impl of fetch/spawn methods for getting data off the web

Cargo.lock

@@ -1640,6 +1640,7 @@ dependencies = [
  "svg 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen 0.2.57 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasm-bindgen-futures 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-test 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "web-sys 0.3.34 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

core/src/backend/audio.rs

@@ -82,7 +82,7 @@ pub trait AudioBackend {
     /// This is only necessary if your particular audio backend needs to know
     /// what the stage frame rate is. Otherwise, you are free to avoid
     /// implementing it.
-    fn set_frame_rate(&mut self, frame_rate: f64) {}
+    fn set_frame_rate(&mut self, _frame_rate: f64) {}
 }
 
 /// Rust does not auto-impl a Trait for Box<Trait> or Deref<Target=Trait>

core/src/backend/navigator.rs

@@ -1,8 +1,11 @@
 //! Browser-related platform functions
 
 use std::collections::HashMap;
+use std::future::Future;
 use swf::avm1::types::SendVarsMethod;
 
+pub type Error = Box<dyn std::error::Error>;
+
 /// Enumerates all possible navigation methods.
 pub enum NavigationMethod {
     /// Indicates that navigation should generate a GET request.
@@ -53,6 +56,19 @@ pub trait NavigatorBackend {
         window: Option<String>,
         vars_method: Option<(NavigationMethod, HashMap<String, String>)>,
     );
+
+    /// Fetch data at a given URL and return it some time in the future.
+    fn fetch(&self, url: String) -> Box<dyn Future<Output = Result<Vec<u8>, Error>>>;
+
+    /// Arrange for a future to be run at some point in the... well, future.
+    ///
+    /// This function must be called to ensure a future is actually computed.
+    /// The future must output an empty value and not hold any stack references
+    /// which would cause it to become invalidated.
+    ///
+    /// TODO: For some reason, `wasm_bindgen_futures` wants unpinnable futures.
+    /// This seems highly limiting.
+    fn spawn_future(&mut self, future: Box<dyn Future<Output = ()> + Unpin + 'static>);
 }
 
 /// A null implementation for platforms that do not live in a web browser.
@@ -78,4 +94,10 @@ impl NavigatorBackend for NullNavigatorBackend {
         _vars_method: Option<(NavigationMethod, HashMap<String, String>)>,
     ) {
     }
+
+    fn fetch(&self, _url: String) -> Box<dyn Future<Output = Result<Vec<u8>, Error>>> {
+        Box::new(async { Err("Fetch IO not implemented".into()) })
+    }
+
+    fn spawn_future(&mut self, _future: Box<dyn Future<Output = ()> + Unpin + 'static>) {}
 }

desktop/src/navigator.rs

@@ -1,8 +1,9 @@
 //! Navigator backend for web
 
 use log;
-use ruffle_core::backend::navigator::{NavigationMethod, NavigatorBackend};
+use ruffle_core::backend::navigator::{Error, NavigationMethod, NavigatorBackend};
 use std::collections::HashMap;
+use std::future::Future;
 use url::Url;
 use webbrowser;
 
@@ -60,4 +61,12 @@ impl NavigatorBackend for ExternalNavigatorBackend {
             Err(e) => log::error!("Could not open URL {}: {}", modified_url, e),
         };
     }
+
+    fn fetch(&self, _url: String) -> Box<dyn Future<Output = Result<Vec<u8>, Error>>> {
+        Box::new(async { Err("Fetch not implemented on desktop!".into()) })
+    }
+
+    fn spawn_future(&mut self, _future: Box<dyn Future<Output = ()> + Unpin + 'static>) {
+        unimplemented!();
+    }
 }

web/Cargo.toml

@@ -24,6 +24,7 @@ svg = "0.6.0"
 percent-encoding = "2.1.0"
 url = "2.1.1"
 wasm-bindgen = "0.2.57"
+wasm-bindgen-futures = "0.4.4"
 
 [dependencies.jpeg-decoder]
 version = "0.1.18"

web/src/navigator.rs

@@ -1,8 +1,10 @@
 //! Navigator backend for web
 
-use ruffle_core::backend::navigator::{NavigationMethod, NavigatorBackend};
+use ruffle_core::backend::navigator::{Error, NavigationMethod, NavigatorBackend};
 use std::collections::HashMap;
+use std::future::Future;
 use wasm_bindgen::JsCast;
+use wasm_bindgen_futures::spawn_local;
 use web_sys::window;
 
 pub struct WebNavigatorBackend {}
@@ -72,4 +74,12 @@ impl NavigatorBackend for WebNavigatorBackend {
             };
         }
     }
+
+    fn fetch(&self, _url: String) -> Box<dyn Future<Output = Result<Vec<u8>, Error>>> {
+        Box::new(async { Ok(Vec::new()) })
+    }
+
+    fn spawn_future(&mut self, future: Box<dyn Future<Output = ()> + Unpin + 'static>) {
+        spawn_local(future)
+    }
 }