switch to a Document trait and introduce Script/Head/Style/Meta components (#2635)

* switch to a Document trait and introduce Script/Head/Style/Meta components

* Fix desktop title

* Insert special elements into the head during the inital SSR render

* Make all head component attributes optional

* hydrate head elements

* improve the server streaming head warning

* Document fullstack head hydration approach

* deduplicate head elements by href

* move Link into head::Link

* document head components

* add meta and title examples

* Fix a few doc examples

* fix formatting

* Add title to playwright tests

* serde is optional on web, but it is enabled by hydrate

* remove leftover console log

packages/html/src/ts/eval.ts

@@ -0,0 +1,108 @@
+// Handle communication between rust and evaluating javascript
+
+export class Channel {
+  pending: any[];
+  waiting: ((data: any) => void)[];
+
+  constructor() {
+    this.pending = [];
+    this.waiting = [];
+  }
+
+  send(data: any) {
+    // If there's a waiting callback, call it
+    if (this.waiting.length > 0) {
+      this.waiting.shift()(data);
+      return;
+    }
+    // Otherwise queue the data
+    this.pending.push(data);
+  }
+
+  async recv(): Promise<any> {
+    return new Promise((resolve, _reject) => {
+      // If data already exists, resolve immediately
+      if (this.pending.length > 0) {
+        resolve(this.pending.shift());
+        return;
+      }
+      // Otherwise queue the resolve callback
+      this.waiting.push(resolve);
+    });
+  }
+}
+
+export class WeakDioxusChannel {
+  inner: WeakRef<DioxusChannel>;
+
+  constructor(channel: DioxusChannel) {
+    this.inner = new WeakRef(channel);
+  }
+
+  // Send data from rust to javascript
+  rustSend(data: any) {
+    let channel = this.inner.deref();
+    if (channel) {
+      channel.rustSend(data);
+    }
+  }
+
+  // Receive data sent from javascript in rust
+  async rustRecv(): Promise<any> {
+    let channel = this.inner.deref();
+    if (channel) {
+      return await channel.rustRecv();
+    }
+  }
+}
+
+export abstract class DioxusChannel {
+  // Return a weak reference to this channel
+  weak(): WeakDioxusChannel {
+    return new WeakDioxusChannel(this);
+  }
+
+  // Send data from rust to javascript
+  abstract rustSend(data: any): void;
+
+  // Receive data sent from javascript in rust
+  abstract rustRecv(): Promise<any>;
+}
+
+export class WebDioxusChannel extends DioxusChannel {
+  js_to_rust: Channel;
+  rust_to_js: Channel;
+  owner: any;
+
+  constructor(owner: any) {
+    super();
+    this.owner = owner;
+    this.js_to_rust = new Channel();
+    this.rust_to_js = new Channel();
+  }
+
+  // Return a weak reference to this channel
+  weak(): WeakDioxusChannel {
+    return new WeakDioxusChannel(this);
+  }
+
+  // Receive message from Rust
+  async recv() {
+    return await this.rust_to_js.recv();
+  }
+
+  // Send message to rust.
+  send(data: any) {
+    this.js_to_rust.send(data);
+  }
+
+  // Send data from rust to javascript
+  rustSend(data: any) {
+    this.rust_to_js.send(data);
+  }
+
+  // Receive data sent from javascript in rust
+  async rustRecv(): Promise<any> {
+    return await this.js_to_rust.recv();
+  }
+}