Web: Implement MonitorHandle (#3801)

Requires getting permission from the user to get "detailed" support.
Also enables users to go fullscreen on specific monitors.
Exposes platform-specific orientation API.

Most functionality depends on browser support, currently only Chromium.

src/platform_impl/web/async/dispatcher.rs

@@ -1,4 +1,7 @@
 use std::cell::Ref;
+use std::cmp::Ordering;
+use std::fmt::{self, Debug, Formatter};
+use std::hash::{Hash, Hasher};
 use std::rc::Rc;
 use std::sync::{Arc, Condvar, Mutex};
 
@@ -9,6 +12,44 @@ pub struct Dispatcher<T: 'static>(Wrapper<T, Arc<Sender<Closure<T>>>, Closure<T>
 
 struct Closure<T>(Box<dyn FnOnce(&T) + Send>);
 
+impl<T> Clone for Dispatcher<T> {
+    fn clone(&self) -> Self {
+        Self(self.0.clone())
+    }
+}
+
+impl<T> Debug for Dispatcher<T> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Dispatcher").finish_non_exhaustive()
+    }
+}
+
+impl<T> Eq for Dispatcher<T> {}
+
+impl<T> Hash for Dispatcher<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.0.hash(state);
+    }
+}
+
+impl<T> Ord for Dispatcher<T> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.0.cmp(&other.0)
+    }
+}
+
+impl<T> PartialEq for Dispatcher<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.0.eq(&other.0)
+    }
+}
+
+impl<T> PartialOrd for Dispatcher<T> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
 impl<T> Dispatcher<T> {
     pub fn new(main_thread: MainThreadMarker, value: T) -> (Self, DispatchRunner<T>) {
         let (sender, receiver) = channel::<Closure<T>>();

src/platform_impl/web/async/wrapper.rs

@@ -1,5 +1,7 @@
 use std::cell::{Ref, RefCell};
+use std::cmp;
 use std::future::Future;
+use std::hash::{Hash, Hasher};
 use std::marker::PhantomData;
 use std::sync::Arc;
 
@@ -81,3 +83,29 @@ impl<V, S: Clone + Send, E> Clone for Wrapper<V, S, E> {
         }
     }
 }
+
+impl<V, S: Clone + Send, E> Eq for Wrapper<V, S, E> {}
+
+impl<V, S: Clone + Send, E> Hash for Wrapper<V, S, E> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        Arc::as_ptr(&self.value.value).hash(state)
+    }
+}
+
+impl<V, S: Clone + Send, E> Ord for Wrapper<V, S, E> {
+    fn cmp(&self, other: &Self) -> cmp::Ordering {
+        Arc::as_ptr(&self.value.value).cmp(&Arc::as_ptr(&other.value.value))
+    }
+}
+
+impl<V, S: Clone + Send, E> PartialOrd for Wrapper<V, S, E> {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl<V, S: Clone + Send, E> PartialEq for Wrapper<V, S, E> {
+    fn eq(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.value.value, &other.value.value)
+    }
+}