compositor: Make input event handling per-WebView (#35716)

This is another step in the move to having a per-WebView renderer. In
this step event handling is made per-WebView. Most events sent to Servo
are sent via the WebView API already, so this just moves more event
handling code to the per-WebView render portion of the compositor.

- ServoRenderer is given shared ownership and interior mutability as
  it is now shared among all WebView(Renderers).
- Some messages coming from other parts of Servo must now carry a
  WebViewId as well so that they can be associated with a particular
  WebView.
- There needs to be some reorganization of `ServoRenderer` in order to
  avoid issues with double borrow of `RefCells`.

Signed-off-by: Delan Azabani <dazabani@igalia.com>
Co-authored-by: Martin Robinson <mrobinson@igalia.com>

components/shared/compositing/constellation_msg.rs

@@ -62,7 +62,7 @@ pub enum ConstellationMsg {
     /// Make none of the webviews focused.
     BlurWebView,
     /// Forward an input event to an appropriate ScriptTask.
-    ForwardInputEvent(InputEvent, Option<CompositorHitTestResult>),
+    ForwardInputEvent(WebViewId, InputEvent, Option<CompositorHitTestResult>),
     /// Requesting a change to the onscreen cursor.
     SetCursor(WebViewId, Cursor),
     /// Enable the sampling profiler, with a given sampling rate and max total sampling duration.

components/shared/compositing/lib.rs

@@ -65,7 +65,7 @@ pub enum CompositorMsg {
     /// Remove a webview.
     RemoveWebView(TopLevelBrowsingContextId),
     /// Script has handled a touch event, and either prevented or allowed default actions.
-    TouchEventProcessed(TouchEventResult),
+    TouchEventProcessed(WebViewId, TouchEventResult),
     /// Composite to a PNG file and return the Image over a passed channel.
     CreatePng(Option<Rect<f32, CSSPixel>>, IpcSender<Option<Image>>),
     /// A reply to the compositor asking if the output image is stable.
@@ -89,9 +89,9 @@ pub enum CompositorMsg {
     /// The load of a page has completed
     LoadComplete(TopLevelBrowsingContextId),
     /// WebDriver mouse button event
-    WebDriverMouseButtonEvent(MouseButtonAction, MouseButton, f32, f32),
+    WebDriverMouseButtonEvent(WebViewId, MouseButtonAction, MouseButton, f32, f32),
     /// WebDriver mouse move event
-    WebDriverMouseMoveEvent(f32, f32),
+    WebDriverMouseMoveEvent(WebViewId, f32, f32),
 
     /// Messages forwarded to the compositor by the constellation from other crates. These
     /// messages are mainly passed on from the compositor to WebRender.

components/shared/embedder/webdriver.rs

@@ -41,9 +41,9 @@ pub enum WebDriverCommandMsg {
     /// Act as if keys were pressed or release in the browsing context with the given ID.
     KeyboardAction(BrowsingContextId, KeyboardEvent),
     /// Act as if the mouse was clicked in the browsing context with the given ID.
-    MouseButtonAction(MouseButtonAction, MouseButton, f32, f32),
+    MouseButtonAction(WebViewId, MouseButtonAction, MouseButton, f32, f32),
     /// Act as if the mouse was moved in the browsing context with the given ID.
-    MouseMoveAction(f32, f32),
+    MouseMoveAction(WebViewId, f32, f32),
     /// Set the window size.
     SetWindowSize(WebViewId, DeviceIntSize, IpcSender<Size2D<f32, CSSPixel>>),
     /// Take a screenshot of the window.