Make media queries more robust

CHANGELOG.md

@@ -63,6 +63,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 - **Breaking:** On Web, `instant` is now replaced by `web_time`.
 - On Windows, port to `windows-sys` version 0.48.0.
 - On Web, fix pen treated as mouse input.
+- On Web, scale factor and dark mode detection are now more robust.
 
 # 0.28.6
 

Cargo.toml

@@ -146,7 +146,6 @@ features = [
     'HtmlElement',
     'KeyboardEvent',
     'MediaQueryList',
-    'MediaQueryListEvent',
     'MouseEvent',
     'Node',
     'PointerEvent',

src/platform_impl/web/web_sys/canvas.rs

@@ -16,8 +16,8 @@ use wasm_bindgen::prelude::wasm_bindgen;
 use wasm_bindgen::{closure::Closure, JsCast, JsValue};
 use wasm_bindgen_futures::JsFuture;
 use web_sys::{
-    AddEventListenerOptions, Event, FocusEvent, HtmlCanvasElement, KeyboardEvent,
-    MediaQueryListEvent, MouseEvent, WheelEvent,
+    AddEventListenerOptions, Event, FocusEvent, HtmlCanvasElement, KeyboardEvent, MouseEvent,
+    WheelEvent,
 };
 
 mod mouse_handler;
@@ -331,12 +331,10 @@ impl Canvas {
     where
         F: 'static + FnMut(bool),
     {
-        let closure =
-            Closure::wrap(
-                Box::new(move |event: MediaQueryListEvent| handler(event.matches()))
-                    as Box<dyn FnMut(_)>,
-            );
-        self.on_dark_mode = MediaQueryListHandle::new("(prefers-color-scheme: dark)", closure);
+        self.on_dark_mode = Some(MediaQueryListHandle::new(
+            "(prefers-color-scheme: dark)",
+            move |mql| handler(mql.matches()),
+        ));
     }
 
     pub fn request_fullscreen(&self) {

src/platform_impl/web/web_sys/media_query_handle.rs

@@ -1,54 +1,47 @@
 use wasm_bindgen::{prelude::Closure, JsCast};
-use web_sys::{MediaQueryList, MediaQueryListEvent};
+use web_sys::MediaQueryList;
 
 pub(super) struct MediaQueryListHandle {
     mql: MediaQueryList,
-    listener: Option<Closure<dyn FnMut(MediaQueryListEvent)>>,
+    closure: Closure<dyn FnMut()>,
 }
 
 impl MediaQueryListHandle {
-    pub fn new(
-        media_query: &str,
-        listener: Closure<dyn FnMut(MediaQueryListEvent)>,
-    ) -> Option<Self> {
+    pub fn new<F>(media_query: &str, mut listener: F) -> Self
+    where
+        F: 'static + FnMut(&MediaQueryList),
+    {
         let window = web_sys::window().expect("Failed to obtain window");
         let mql = window
             .match_media(media_query)
-            .ok()
-            .flatten()
-            .and_then(|mql| {
-                mql.add_listener_with_opt_callback(Some(listener.as_ref().unchecked_ref()))
-                    .map(|_| mql)
-                    .ok()
-            });
-        mql.map(|mql| Self {
-            mql,
-            listener: Some(listener),
-        })
+            .expect("Failed to parse media query")
+            .expect("Found empty media query");
+
+        let closure = Closure::new({
+            let mql = mql.clone();
+            move || listener(&mql)
+        });
+        // TODO: Replace obsolete `addListener()` with `addEventListener()` and use
+        // `MediaQueryListEvent` instead of cloning the `MediaQueryList`.
+        // Requires Safari v14.
+        mql.add_listener_with_opt_callback(Some(closure.as_ref().unchecked_ref()))
+            .expect("Invalid listener");
+
+        Self { mql, closure }
     }
 
     pub fn mql(&self) -> &MediaQueryList {
         &self.mql
     }
-
-    /// Removes the listener and returns the original listener closure, which
-    /// can be reused.
-    pub fn remove(mut self) -> Closure<dyn FnMut(MediaQueryListEvent)> {
-        let listener = self.listener.take().unwrap_or_else(|| unreachable!());
-        remove_listener(&self.mql, &listener);
-        listener
-    }
 }
 
 impl Drop for MediaQueryListHandle {
     fn drop(&mut self) {
-        if let Some(listener) = self.listener.take() {
-            remove_listener(&self.mql, &listener);
-        }
+        remove_listener(&self.mql, &self.closure);
     }
 }
 
-fn remove_listener(mql: &MediaQueryList, listener: &Closure<dyn FnMut(MediaQueryListEvent)>) {
+fn remove_listener(mql: &MediaQueryList, listener: &Closure<dyn FnMut()>) {
     mql.remove_listener_with_opt_callback(Some(listener.as_ref().unchecked_ref()))
         .unwrap_or_else(|e| {
             web_sys::console::error_2(&"Error removing media query listener".into(), &e)

src/platform_impl/web/web_sys/scaling.rs

@@ -1,9 +1,9 @@
+use web_sys::MediaQueryList;
+
 use super::super::ScaleChangeArgs;
 use super::media_query_handle::MediaQueryListHandle;
 
 use std::{cell::RefCell, rc::Rc};
-use wasm_bindgen::prelude::Closure;
-use web_sys::MediaQueryListEvent;
 
 pub struct ScaleChangeDetector(Rc<RefCell<ScaleChangeDetectorInternal>>);
 
@@ -37,52 +37,57 @@ impl ScaleChangeDetectorInternal {
         }));
 
         let weak_self = Rc::downgrade(&new_self);
-        let closure = Closure::wrap(Box::new(move |event: MediaQueryListEvent| {
+        let mql = Self::create_mql(move |mql| {
             if let Some(rc_self) = weak_self.upgrade() {
-                rc_self.borrow_mut().handler(event);
+                Self::handler(rc_self, mql);
             }
-        }) as Box<dyn FnMut(_)>);
-
-        let mql = Self::create_mql(closure);
+        });
         {
             let mut borrowed_self = new_self.borrow_mut();
-            borrowed_self.mql = mql;
+            borrowed_self.mql = Some(mql);
         }
         new_self
     }
 
-    fn create_mql(
-        closure: Closure<dyn FnMut(MediaQueryListEvent)>,
-    ) -> Option<MediaQueryListHandle> {
+    fn create_mql<F>(closure: F) -> MediaQueryListHandle
+    where
+        F: 'static + FnMut(&MediaQueryList),
+    {
         let current_scale = super::scale_factor();
-        // This media query initially matches the current `devicePixelRatio`.
-        // We add 0.0001 to the lower and upper bounds such that it won't fail
-        // due to floating point precision limitations.
+        // TODO: Remove `-webkit-device-pixel-ratio`. Requires Safari v16.
         let media_query = format!(
-            "(min-resolution: {min_scale:.4}dppx) and (max-resolution: {max_scale:.4}dppx),
-             (-webkit-min-device-pixel-ratio: {min_scale:.4}) and (-webkit-max-device-pixel-ratio: {max_scale:.4})",
-            min_scale = current_scale - 0.0001, max_scale= current_scale + 0.0001,
+            "(resolution: {current_scale}dppx),
+             (-webkit-device-pixel-ratio: {current_scale})",
         );
         let mql = MediaQueryListHandle::new(&media_query, closure);
-        if let Some(mql) = &mql {
-            assert!(mql.mql().matches());
-        }
+        assert!(
+            mql.mql().matches(),
+            "created media query doesn't match, {current_scale} != {}",
+            super::scale_factor()
+        );
         mql
     }
 
-    fn handler(&mut self, _event: MediaQueryListEvent) {
-        let mql = self
-            .mql
-            .take()
-            .expect("DevicePixelRatioChangeDetector::mql should not be None");
-        let closure = mql.remove();
+    fn handler(this: Rc<RefCell<Self>>, mql: &MediaQueryList) {
+        let weak_self = Rc::downgrade(&this);
+        let mut this = this.borrow_mut();
+        let old_scale = this.last_scale;
         let new_scale = super::scale_factor();
-        (self.callback)(ScaleChangeArgs {
-            old_scale: self.last_scale,
+        (this.callback)(ScaleChangeArgs {
+            old_scale,
             new_scale,
         });
-        let new_mql = Self::create_mql(closure);
-        self.mql = new_mql;
-        self.last_scale = new_scale;
+
+        // If this matches, then the scale factor is back to it's
+        // old value again, so we won't need to update the query.
+        if !mql.matches() {
+            let new_mql = Self::create_mql(move |mql| {
+                if let Some(rc_self) = weak_self.upgrade() {
+                    Self::handler(rc_self, mql);
+                }
+            });
+            this.mql = Some(new_mql);
+            this.last_scale = new_scale;
+        }
     }
 }