Use only non-send futures

maplibre/Cargo.toml

@@ -12,13 +12,13 @@ readme = "../README.md"
 web-webgl = ["wgpu/webgl"]
 # Enable tracing using tracy on desktop/mobile and the chrome profiler on web
 trace = ["tracing-subscriber", "tracing-tracy", "tracy-client"]
-no-thread-safe-futures = []
 embed-static-tiles = ["maplibre-build-tools/sqlite"]
 headless = ["png"]
 
 
 [target.'cfg(any(target_os = "macos", target_os = "ios", target_os = "linux", target_os = "android", target_os = "windows"))'.dependencies]
 tokio = { version = "1.20.1", features = ["macros", "rt", "rt-multi-thread", "sync", "time"] }
+tokio-util = { version = "0.7.1", features = ["rt"] }
 env_logger = "0.9.0"
 reqwest = { version = "0.11.11", default-features = false, features = ["rustls-tls", "gzip"] }
 reqwest-middleware-cache = "0.1.1"

maplibre/src/io/scheduler.rs

@@ -27,15 +27,6 @@ where
 
 /// Can schedule a task from a future factory and a shared state.
 pub trait ScheduleMethod: 'static {
-    #[cfg(not(feature = "no-thread-safe-futures"))]
-    fn schedule<T>(
-        &self,
-        future_factory: impl (FnOnce() -> T) + Send + 'static,
-    ) -> Result<(), Error>
-    where
-        T: Future<Output = ()> + Send + 'static;
-
-    #[cfg(feature = "no-thread-safe-futures")]
     fn schedule<T>(
         &self,
         future_factory: impl (FnOnce() -> T) + Send + 'static,

maplibre/src/io/source_client.rs

@@ -5,16 +5,12 @@ use async_trait::async_trait;
 use crate::{coords::WorldTileCoords, error::Error, style::source::TileAddressingScheme};
 
 /// A closure that returns a HTTP client.
-pub type HTTPClientFactory<HC> = dyn Fn() -> HC;
+pub type HttpClientFactory<HC> = dyn Fn() -> HC;
 
-/// On the web platform futures are not thread-safe (i.e. not Send). This means we need to tell
-/// async_trait that these bounds should not be placed on the async trait:
-/// [https://github.com/dtolnay/async-trait/blob/b70720c4c1cc0d810b7446efda44f81310ee7bf2/README.md#non-threadsafe-futures](https://github.com/dtolnay/async-trait/blob/b70720c4c1cc0d810b7446efda44f81310ee7bf2/README.md#non-threadsafe-futures)
-///
-/// Users of this library can decide whether futures from the HTTPClient are thread-safe or not via
-/// the future "no-thread-safe-futures". Tokio futures are thread-safe.
-#[cfg_attr(feature = "no-thread-safe-futures", async_trait(?Send))]
-#[cfg_attr(not(feature = "no-thread-safe-futures"), async_trait)]
+// On the web platform futures are not thread-safe (i.e. not Send). This means we need to tell
+// async_trait that these bounds should not be placed on the async trait:
+// https://github.com/dtolnay/async-trait/blob/b70720c4c1cc0d810b7446efda44f81310ee7bf2/README.md#non-threadsafe-futures
+#[async_trait(?Send)]
 pub trait HttpClient: Clone + Sync + Send + 'static {
     async fn fetch(&self, url: &str) -> Result<Vec<u8>, Error>;
 }

maplibre/src/platform/noweb/http_client.rs

@@ -39,7 +39,7 @@ impl ReqwestHttpClient {
     }
 }
 
-#[async_trait]
+#[async_trait(?Send)]
 impl HttpClient for ReqwestHttpClient {
     async fn fetch(&self, url: &str) -> Result<Vec<u8>, Error> {
         let response = self.client.get(url).send().await?;

maplibre/src/platform/noweb/schedule_method.rs

@@ -1,22 +1,34 @@
 use std::future::Future;
 
+use tokio::task;
+use tokio_util::task::LocalPoolHandle;
+
 use crate::{error::Error, ScheduleMethod};
 
 /// Multi-threading with Tokio.
-pub struct TokioScheduleMethod;
+pub struct TokioScheduleMethod {
+    pool: LocalPoolHandle,
+}
 
 impl TokioScheduleMethod {
     pub fn new() -> Self {
-        Self {}
+        Self {
+            pool: LocalPoolHandle::new(4),
+        }
     }
 }
 
 impl ScheduleMethod for TokioScheduleMethod {
     fn schedule<T>(&self, future_factory: impl FnOnce() -> T + Send + 'static) -> Result<(), Error>
     where
-        T: Future<Output = ()> + Send + 'static,
+        T: Future<Output = ()> + 'static,
     {
-        tokio::task::spawn((future_factory)());
+        self.pool.spawn_pinned(|| {
+            let unsend_data = (future_factory)();
+
+            async move { unsend_data.await }
+        });
+
         Ok(())
     }
 }

web/Cargo.toml

@@ -19,7 +19,7 @@ crate-type = ["cdylib", "rlib"]
 
 [dependencies]
 async-trait = "0.1.56"
-maplibre = { path = "../maplibre", features = ["no-thread-safe-futures"] }
+maplibre = { path = "../maplibre", features = [] }
 maplibre-winit = { path = "../maplibre-winit", version = "0.0.1"  }
 log = "0.4.17"