Web: use raw data in DeviceEvent::MouseMotion (#3803)

Only supported on Chrome MacOS and Windows.

src/changelog/unreleased.md

@@ -44,6 +44,9 @@ changelog entry.
 
 - Add `ActiveEventLoop::create_proxy()`.
 - On Web, implement `Error` for `platform::web::CustomCursorError`.
+- On Web, add `ActiveEventLoopExtWeb::is_cursor_lock_raw()` to determine if
+  `DeviceEvent::MouseMotion` is returning raw data, not OS accelerated, when using
+  `CursorGrabMode::Locked`.
 
 ### Changed
 
@@ -71,6 +74,8 @@ changelog entry.
   `EventLoopExtRunOnDemand::run_app_on_demand` to accept a `impl ApplicationHandler` directly,
   instead of requiring a `&mut` reference to it.
 - On Web, `Window::canvas()` now returns a reference.
+- On Web, `CursorGrabMode::Locked` now lets `DeviceEvent::MouseMotion` return raw data, not OS
+  accelerated, if the browser supports it.
 
 ### Removed
 

src/event.rs

@@ -467,6 +467,22 @@ pub enum DeviceEvent {
     ///
     /// This represents raw, unfiltered physical motion. Not to be confused with
     /// [`WindowEvent::CursorMoved`].
+    ///
+    /// ## Platform-specific
+    ///
+    /// **Web:** Only returns raw data, not OS accelerated, if [`CursorGrabMode::Locked`] is used
+    /// and browser support is available, see
+    #[cfg_attr(
+        any(web_platform, docsrs),
+        doc = "[`ActiveEventLoopExtWeb::is_cursor_lock_raw()`][crate::platform::web::ActiveEventLoopExtWeb::is_cursor_lock_raw()]."
+    )]
+    #[cfg_attr(
+        not(any(web_platform, docsrs)),
+        doc = "`ActiveEventLoopExtWeb::is_cursor_lock_raw()`."
+    )]
+    ///
+    #[rustfmt::skip]
+    /// [`CursorGrabMode::Locked`]: crate::window::CursorGrabMode::Locked
     MouseMotion {
         /// (x, y) change in position in unspecified units.
         ///

src/platform/web.rs

@@ -84,6 +84,14 @@ pub trait WindowExtWeb {
     /// Some events are impossible to prevent. E.g. Firefox allows to access the native browser
     /// context menu with Shift+Rightclick.
     fn set_prevent_default(&self, prevent_default: bool);
+
+    /// Returns whether using [`CursorGrabMode::Locked`] returns raw, un-accelerated mouse input.
+    ///
+    /// This is the same as [`ActiveEventLoop::is_cursor_lock_raw()`], and is provided for
+    /// convenience.
+    ///
+    /// [`CursorGrabMode::Locked`]: crate::window::CursorGrabMode::Locked
+    fn is_cursor_lock_raw(&self) -> bool;
 }
 
 impl WindowExtWeb for Window {
@@ -99,6 +107,10 @@ impl WindowExtWeb for Window {
     fn set_prevent_default(&self, prevent_default: bool) {
         self.window.set_prevent_default(prevent_default)
     }
+
+    fn is_cursor_lock_raw(&self) -> bool {
+        self.window.is_cursor_lock_raw()
+    }
 }
 
 pub trait WindowAttributesExtWeb {
@@ -262,6 +274,11 @@ pub trait ActiveEventLoopExtWeb {
     /// Async version of [`ActiveEventLoop::create_custom_cursor()`] which waits until the
     /// cursor has completely finished loading.
     fn create_custom_cursor_async(&self, source: CustomCursorSource) -> CustomCursorFuture;
+
+    /// Returns whether using [`CursorGrabMode::Locked`] returns raw, un-accelerated mouse input.
+    ///
+    /// [`CursorGrabMode::Locked`]: crate::window::CursorGrabMode::Locked
+    fn is_cursor_lock_raw(&self) -> bool;
 }
 
 impl ActiveEventLoopExtWeb for ActiveEventLoop {
@@ -289,6 +306,11 @@ impl ActiveEventLoopExtWeb for ActiveEventLoop {
     fn wait_until_strategy(&self) -> WaitUntilStrategy {
         self.p.wait_until_strategy()
     }
+
+    #[inline]
+    fn is_cursor_lock_raw(&self) -> bool {
+        self.p.is_cursor_lock_raw()
+    }
 }
 
 /// Strategy used for [`ControlFlow::Poll`][crate::event_loop::ControlFlow::Poll].

src/platform_impl/web/event_loop/window_target.rs

@@ -8,7 +8,7 @@ use std::rc::Rc;
 use web_sys::Element;
 
 use super::super::monitor::MonitorHandle;
-use super::super::KeyEventExtra;
+use super::super::{lock, KeyEventExtra};
 use super::device::DeviceId;
 use super::runner::{EventWrapper, WeakShared};
 use super::window::WindowId;
@@ -652,6 +652,10 @@ impl ActiveEventLoop {
         self.runner.wait_until_strategy()
     }
 
+    pub(crate) fn is_cursor_lock_raw(&self) -> bool {
+        lock::is_cursor_lock_raw(self.runner.window(), self.runner.document())
+    }
+
     pub(crate) fn waker(&self) -> Waker<WeakShared> {
         self.runner.waker()
     }

src/platform_impl/web/lock.rs

@@ -0,0 +1,82 @@
+use std::cell::OnceCell;
+
+use js_sys::{Object, Promise};
+use tracing::error;
+use wasm_bindgen::closure::Closure;
+use wasm_bindgen::prelude::wasm_bindgen;
+use wasm_bindgen::{JsCast, JsValue};
+use web_sys::{console, Document, DomException, Element, Window};
+
+pub(crate) fn is_cursor_lock_raw(window: &Window, document: &Document) -> bool {
+    thread_local! {
+        static IS_CURSOR_LOCK_RAW: OnceCell<bool> = const { OnceCell::new() };
+    }
+
+    IS_CURSOR_LOCK_RAW.with(|cell| {
+        *cell.get_or_init(|| {
+            // TODO: Remove when Chrome can better advertise that they don't support unaccelerated
+            // movement on Linux.
+            // See <https://issues.chromium.org/issues/40833850>.
+            if super::web_sys::chrome_linux(window) {
+                return false;
+            }
+
+            let element: ElementExt = document.create_element("div").unwrap().unchecked_into();
+            let promise = element.request_pointer_lock();
+
+            if promise.is_undefined() {
+                false
+            } else {
+                thread_local! {
+                    static REJECT_HANDLER: Closure<dyn FnMut(JsValue)> = Closure::new(|_| ());
+                }
+
+                let promise: Promise = promise.unchecked_into();
+                let _ = REJECT_HANDLER.with(|handler| promise.catch(handler));
+                true
+            }
+        })
+    })
+}
+
+pub(crate) fn request_pointer_lock(window: &Window, document: &Document, element: &Element) {
+    if is_cursor_lock_raw(window, document) {
+        thread_local! {
+            static REJECT_HANDLER: Closure<dyn FnMut(JsValue)> = Closure::new(|error: JsValue| {
+                if let Some(error) = error.dyn_ref::<DomException>() {
+                        error!("Failed to lock pointer. {}: {}", error.name(), error.message());
+                } else {
+                    console::error_1(&error);
+                    error!("Failed to lock pointer");
+                }
+            });
+        }
+
+        let element: &ElementExt = element.unchecked_ref();
+        let options: PointerLockOptions = Object::new().unchecked_into();
+        options.set_unadjusted_movement(true);
+        let _ = REJECT_HANDLER
+            .with(|handler| element.request_pointer_lock_with_options(&options).catch(handler));
+    } else {
+        element.request_pointer_lock();
+    }
+}
+
+#[wasm_bindgen]
+extern "C" {
+    type ElementExt;
+
+    #[wasm_bindgen(method, js_name = requestPointerLock)]
+    fn request_pointer_lock(this: &ElementExt) -> JsValue;
+
+    #[wasm_bindgen(method, js_name = requestPointerLock)]
+    fn request_pointer_lock_with_options(
+        this: &ElementExt,
+        options: &PointerLockOptions,
+    ) -> Promise;
+
+    type PointerLockOptions;
+
+    #[wasm_bindgen(method, setter, js_name = unadjustedMovement)]
+    fn set_unadjusted_movement(this: &PointerLockOptions, value: bool);
+}

src/platform_impl/web/mod.rs

@@ -26,6 +26,7 @@ mod device;
 mod error;
 mod event_loop;
 mod keyboard;
+mod lock;
 mod main_thread;
 mod monitor;
 mod web_sys;

src/platform_impl/web/web_sys/canvas.rs

@@ -176,15 +176,6 @@ impl Canvas {
         })
     }
 
-    pub fn set_cursor_lock(&self, lock: bool) -> Result<(), RootOE> {
-        if lock {
-            self.raw().request_pointer_lock();
-        } else {
-            self.common.document.exit_pointer_lock();
-        }
-        Ok(())
-    }
-
     pub fn set_attribute(&self, attribute: &str, value: &str) {
         self.common
             .raw

src/platform_impl/web/web_sys/mod.rs

@@ -9,7 +9,7 @@ mod pointer;
 mod resize_scaling;
 mod schedule;
 
-use std::sync::OnceLock;
+use std::cell::OnceCell;
 
 use js_sys::Array;
 use wasm_bindgen::closure::Closure;
@@ -173,9 +173,24 @@ pub enum Engine {
     WebKit,
 }
 
-pub fn engine(window: &Window) -> Option<Engine> {
-    static ENGINE: OnceLock<Option<Engine>> = OnceLock::new();
+struct UserAgentData {
+    engine: Option<Engine>,
+    chrome_linux: bool,
+}
 
+thread_local! {
+    static USER_AGENT_DATA: OnceCell<UserAgentData> = const { OnceCell::new() };
+}
+
+pub fn chrome_linux(window: &Window) -> bool {
+    USER_AGENT_DATA.with(|data| data.get_or_init(|| user_agent(window)).chrome_linux)
+}
+
+pub fn engine(window: &Window) -> Option<Engine> {
+    USER_AGENT_DATA.with(|data| data.get_or_init(|| user_agent(window)).engine)
+}
+
+fn user_agent(window: &Window) -> UserAgentData {
     #[wasm_bindgen]
     extern "C" {
         #[wasm_bindgen(extends = Navigator)]
@@ -189,16 +204,19 @@ pub fn engine(window: &Window) -> Option<Engine> {
         #[wasm_bindgen(method, getter)]
         fn brands(this: &NavigatorUaData) -> Array;
 
+        #[wasm_bindgen(method, getter)]
+        fn platform(this: &NavigatorUaData) -> String;
+
         type NavigatorUaBrandVersion;
 
         #[wasm_bindgen(method, getter)]
         fn brand(this: &NavigatorUaBrandVersion) -> String;
     }
 
-    *ENGINE.get_or_init(|| {
-        let navigator: NavigatorExt = window.navigator().unchecked_into();
+    let navigator: NavigatorExt = window.navigator().unchecked_into();
 
-        if let Some(data) = navigator.user_agent_data() {
+    if let Some(data) = navigator.user_agent_data() {
+        let engine = 'engine: {
             for brand in data
                 .brands()
                 .iter()
@@ -206,18 +224,28 @@ pub fn engine(window: &Window) -> Option<Engine> {
                 .map(|brand| brand.brand())
             {
                 match brand.as_str() {
-                    "Chromium" => return Some(Engine::Chromium),
+                    "Chromium" => break 'engine Some(Engine::Chromium),
                     // TODO: verify when Firefox actually implements it.
-                    "Gecko" => return Some(Engine::Gecko),
+                    "Gecko" => break 'engine Some(Engine::Gecko),
                     // TODO: verify when Safari actually implements it.
-                    "WebKit" => return Some(Engine::WebKit),
+                    "WebKit" => break 'engine Some(Engine::WebKit),
                     _ => (),
                 }
             }
 
             None
-        } else {
-            let data = navigator.user_agent().ok()?;
+        };
+
+        let chrome_linux = matches!(engine, Some(Engine::Chromium))
+            .then(|| data.platform() == "Linux")
+            .unwrap_or(false);
+
+        UserAgentData { engine, chrome_linux }
+    } else {
+        let engine = 'engine: {
+            let Ok(data) = navigator.user_agent() else {
+                break 'engine None;
+            };
 
             if data.contains("Chrome/") {
                 Some(Engine::Chromium)
@@ -228,6 +256,8 @@ pub fn engine(window: &Window) -> Option<Engine> {
             } else {
                 None
             }
-        }
-    })
+        };
+
+        UserAgentData { engine, chrome_linux: false }
+    }
 }

src/platform_impl/web/window.rs

@@ -8,7 +8,7 @@ use web_sys::HtmlCanvasElement;
 use super::main_thread::{MainThreadMarker, MainThreadSafe};
 use super::monitor::MonitorHandle;
 use super::r#async::Dispatcher;
-use super::{backend, ActiveEventLoop, Fullscreen};
+use super::{backend, lock, ActiveEventLoop, Fullscreen};
 use crate::dpi::{PhysicalPosition, PhysicalSize, Position, Size};
 use crate::error::{ExternalError, NotSupportedError, OsError as RootOE};
 use crate::icon::Icon;
@@ -78,6 +78,12 @@ impl Window {
         self.inner.dispatch(move |inner| inner.canvas.prevent_default.set(prevent_default))
     }
 
+    pub(crate) fn is_cursor_lock_raw(&self) -> bool {
+        self.inner.queue(move |inner| {
+            lock::is_cursor_lock_raw(inner.canvas.window(), inner.canvas.document())
+        })
+    }
+
     #[cfg(feature = "rwh_06")]
     #[inline]
     pub fn raw_window_handle_rwh_06(&self) -> Result<rwh_06::RawWindowHandle, rwh_06::HandleError> {
@@ -235,15 +241,19 @@ impl Inner {
 
     #[inline]
     pub fn set_cursor_grab(&self, mode: CursorGrabMode) -> Result<(), ExternalError> {
-        let lock = match mode {
-            CursorGrabMode::None => false,
-            CursorGrabMode::Locked => true,
+        match mode {
+            CursorGrabMode::None => self.canvas.document().exit_pointer_lock(),
+            CursorGrabMode::Locked => lock::request_pointer_lock(
+                self.canvas.window(),
+                self.canvas.document(),
+                self.canvas.raw(),
+            ),
             CursorGrabMode::Confined => {
                 return Err(ExternalError::NotSupported(NotSupportedError::new()))
             },
-        };
+        }
 
-        self.canvas.set_cursor_lock(lock).map_err(ExternalError::Os)
+        Ok(())
     }
 
     #[inline]