libservo: Combine LoadStart, HeadParsed, and LoadComplete` messages (#35260)

These will be a single method in the upcoming `WebView` delegate, so it
makes sense to also combine the internal message to match this. In
addition, since `LoadStatus` is now exposed to the API if there is ever
the need to add more statuses or to move to an event-based version, the
API is already set up for this.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/constellation/tracing.rs

@@ -121,6 +121,8 @@ mod from_compositor {
 }
 
 mod from_script {
+    use embedder_traits::LoadStatus;
+
     use super::LogTarget;
 
     macro_rules! target {
@@ -222,11 +224,17 @@ mod from_script {
                 Self::SetClipboardContents(..) => target_variant!("SetClipboardContents"),
                 Self::SetCursor(..) => target_variant!("SetCursor"),
                 Self::NewFavicon(..) => target_variant!("NewFavicon"),
-                Self::HeadParsed(..) => target_variant!("HeadParsed"),
                 Self::HistoryChanged(..) => target_variant!("HistoryChanged"),
                 Self::SetFullscreenState(..) => target_variant!("SetFullscreenState"),
-                Self::LoadStart(..) => target_variant!("LoadStart"),
-                Self::LoadComplete(..) => target_variant!("LoadComplete"),
+                Self::NotifyLoadStatusChanged(_, LoadStatus::Started) => {
+                    target_variant!("NotifyLoadStatusChanged(LoadStatus::Started)")
+                },
+                Self::NotifyLoadStatusChanged(_, LoadStatus::HeadParsed) => {
+                    target_variant!("NotifyLoadStatusChanged(LoadStatus::HeadParsed)")
+                },
+                Self::NotifyLoadStatusChanged(_, LoadStatus::Complete) => {
+                    target_variant!("NotifyLoadStatusChanged(LoadStatus::Complete")
+                },
                 Self::Panic(..) => target_variant!("Panic"),
                 Self::GetSelectedBluetoothDevice(..) => {
                     target_variant!("GetSelectedBluetoothDevice")

components/script/dom/document.rs

@@ -24,8 +24,8 @@ use cssparser::match_ignore_ascii_case;
 use devtools_traits::ScriptToDevtoolsControlMsg;
 use dom_struct::dom_struct;
 use embedder_traits::{
-    ClipboardEventType, EmbedderMsg, MouseButton, MouseEventType, TouchEventType, TouchId,
-    WheelDelta,
+    ClipboardEventType, EmbedderMsg, LoadStatus, MouseButton, MouseEventType, TouchEventType,
+    TouchId, WheelDelta,
 };
 use encoding_rs::{Encoding, UTF_8};
 use euclid::default::{Point2D, Rect, Size2D};
@@ -1032,13 +1032,19 @@ impl Document {
         match state {
             DocumentReadyState::Loading => {
                 if self.window().is_top_level() {
-                    self.send_to_embedder(EmbedderMsg::LoadStart(self.webview_id()));
+                    self.send_to_embedder(EmbedderMsg::NotifyLoadStatusChanged(
+                        self.webview_id(),
+                        LoadStatus::Started,
+                    ));
                     self.send_to_embedder(EmbedderMsg::Status(self.webview_id(), None));
                 }
             },
             DocumentReadyState::Complete => {
                 if self.window().is_top_level() {
-                    self.send_to_embedder(EmbedderMsg::LoadComplete(self.webview_id()));
+                    self.send_to_embedder(EmbedderMsg::NotifyLoadStatusChanged(
+                        self.webview_id(),
+                        LoadStatus::Complete,
+                    ));
                 }
                 update_with_current_instant(&self.dom_complete);
             },

components/script/dom/htmlbodyelement.rs

@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use dom_struct::dom_struct;
-use embedder_traits::EmbedderMsg;
+use embedder_traits::{EmbedderMsg, LoadStatus};
 use html5ever::{local_name, namespace_url, ns, LocalName, Prefix};
 use js::rust::HandleObject;
 use servo_url::ServoUrl;
@@ -153,7 +153,10 @@ impl VirtualMethods for HTMLBodyElement {
         let window = self.owner_window();
         window.prevent_layout_until_load_event();
         if window.is_top_level() {
-            window.send_to_embedder(EmbedderMsg::HeadParsed(window.webview_id()));
+            window.send_to_embedder(EmbedderMsg::NotifyLoadStatusChanged(
+                window.webview_id(),
+                LoadStatus::HeadParsed,
+            ));
         }
     }
 

components/shared/embedder/lib.rs

@@ -193,16 +193,12 @@ pub enum EmbedderMsg {
     SetCursor(WebViewId, Cursor),
     /// A favicon was detected
     NewFavicon(WebViewId, ServoUrl),
-    /// `<head>` tag finished parsing
-    HeadParsed(WebViewId),
     /// The history state has changed.
     HistoryChanged(WebViewId, Vec<ServoUrl>, usize),
     /// Enter or exit fullscreen
     SetFullscreenState(WebViewId, bool),
-    /// The load of a page has begun
-    LoadStart(WebViewId),
-    /// The load of a page has completed
-    LoadComplete(WebViewId),
+    /// The [`LoadStatus`] of the Given `WebView` has changed.
+    NotifyLoadStatusChanged(WebViewId, LoadStatus),
     WebResourceRequested(
         Option<WebViewId>,
         WebResourceRequest,
@@ -286,11 +282,11 @@ impl Debug for EmbedderMsg {
             EmbedderMsg::SetClipboardContents(..) => write!(f, "SetClipboardContents"),
             EmbedderMsg::SetCursor(..) => write!(f, "SetCursor"),
             EmbedderMsg::NewFavicon(..) => write!(f, "NewFavicon"),
-            EmbedderMsg::HeadParsed(..) => write!(f, "HeadParsed"),
             EmbedderMsg::HistoryChanged(..) => write!(f, "HistoryChanged"),
             EmbedderMsg::SetFullscreenState(..) => write!(f, "SetFullscreenState"),
-            EmbedderMsg::LoadStart(..) => write!(f, "LoadStart"),
-            EmbedderMsg::LoadComplete(..) => write!(f, "LoadComplete"),
+            EmbedderMsg::NotifyLoadStatusChanged(_, status) => {
+                write!(f, "NotifyLoadStatusChanged({status:?})")
+            },
             EmbedderMsg::WebResourceRequested(..) => write!(f, "WebResourceRequested"),
             EmbedderMsg::Panic(..) => write!(f, "Panic"),
             EmbedderMsg::GetSelectedBluetoothDevice(..) => write!(f, "GetSelectedBluetoothDevice"),
@@ -736,3 +732,17 @@ pub enum MediaSessionActionType {
     /// The action intent is to move the playback time to a specific time.
     SeekTo,
 }
+
+/// The status of the load in this `WebView`.
+#[derive(Clone, Copy, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub enum LoadStatus {
+    /// The load has started, but the headers have not yet been parsed.
+    Started,
+    /// The `<head>` tag has been parsed in the currently loading page. At this point the page's
+    /// `HTMLBodyElement` is now available in the DOM.
+    HeadParsed,
+    /// The `Document` and all subresources have loaded. This is equivalent to
+    /// `document.readyState` == `complete`.
+    /// See <https://developer.mozilla.org/en-US/docs/Web/API/Document/readyState>
+    Complete,
+}