script: Ensure that leaving the WebView sets the cursor back to the default cursor (#38759)

This changes makes a variety of changes to ensure that the cursor is set
back to the default cursor when it leaves the `WebView`:

1. Display list updates can come after a mouse leaves the `WebView`, so
   when refreshing the cursor after the update, base the updated cursor
   on the last hovered location in the `DocumentEventHandler`, rather
   than the compositor. This allows us to catch when the last hovered
   position is `None` (ie the cursor has left the `WebView`).
2. When handling `MouseLeftViewport` events for the cursor leaving the
   entire WebView, properly set the
   MouseLeftViewport::focus_moving_to_another_iframe` on the input event
   passed to the script thread.
3. When moving out of the `WebView` entirely, explicitly ask the
   embedder to set the cursor back to the default.

Testing: This change adds a unit test verifying this behavior.
Fixes: #38710.

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

components/shared/constellation/lib.rs

@@ -22,7 +22,6 @@ use embedder_traits::{
     CompositorHitTestResult, FocusId, InputEvent, JavaScriptEvaluationId, MediaSessionActionType,
     Theme, TraversalId, ViewportDetails, WebDriverCommandMsg, WebDriverCommandResponse,
 };
-use euclid::Point2D;
 pub use from_script_message::*;
 use ipc_channel::ipc::IpcSender;
 use malloc_size_of_derive::MallocSizeOf;
@@ -32,7 +31,6 @@ use servo_config::prefs::PrefValue;
 use servo_url::{ImmutableOrigin, ServoUrl};
 pub use structured_data::*;
 use strum_macros::IntoStaticStr;
-use style_traits::CSSPixel;
 use webrender_api::units::LayoutVector2D;
 use webrender_api::{ExternalScrollId, ImageKey};
 
@@ -78,9 +76,10 @@ pub enum EmbedderToConstellationMessage {
     BlurWebView,
     /// Forward an input event to an appropriate ScriptTask.
     ForwardInputEvent(WebViewId, InputEvent, Option<CompositorHitTestResult>),
-    /// Request that the given pipeline do a hit test at the location and reset the
-    /// cursor accordingly. This happens after a display list update is rendered.
-    RefreshCursor(PipelineId, Point2D<f32, CSSPixel>),
+    /// Request that the given pipeline refresh the cursor by doing a hit test at the most
+    /// recently hovered cursor position and resetting the cursor. This happens after a
+    /// display list update is rendered.
+    RefreshCursor(PipelineId),
     /// Enable the sampling profiler, with a given sampling rate and max total sampling duration.
     ToggleProfiler(Duration, Duration),
     /// Request to exit from fullscreen mode

components/shared/embedder/lib.rs

@@ -55,9 +55,10 @@ pub enum ShutdownState {
 /// A cursor for the window. This is different from a CSS cursor (see
 /// `CursorKind`) in that it has no `Auto` value.
 #[repr(u8)]
-#[derive(Clone, Copy, Debug, Deserialize, Eq, MallocSizeOf, PartialEq, Serialize)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, Eq, MallocSizeOf, PartialEq, Serialize)]
 pub enum Cursor {
     None,
+    #[default]
     Default,
     Pointer,
     ContextMenu,

components/shared/script/lib.rs

@@ -32,7 +32,7 @@ use embedder_traits::{
     CompositorHitTestResult, FocusSequenceNumber, InputEvent, JavaScriptEvaluationId,
     MediaSessionActionType, Theme, ViewportDetails, WebDriverScriptCommand,
 };
-use euclid::{Point2D, Rect, Scale, Size2D, UnknownUnit};
+use euclid::{Rect, Scale, Size2D, UnknownUnit};
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use keyboard_types::Modifiers;
 use malloc_size_of_derive::MallocSizeOf;
@@ -147,9 +147,10 @@ pub enum ScriptThreadMessage {
     ExitScriptThread,
     /// Sends a DOM event.
     SendInputEvent(PipelineId, ConstellationInputEvent),
-    /// Ask that the given pipeline refreshes the cursor (after a display list render) based
-    /// on the hit test at the given point.
-    RefreshCursor(PipelineId, Point2D<f32, CSSPixel>),
+    /// Request that the given pipeline refresh the cursor by doing a hit test at the most
+    /// recently hovered cursor position and resetting the cursor. This happens after a
+    /// display list update is rendered.
+    RefreshCursor(PipelineId),
     /// Notifies script of the viewport.
     Viewport(PipelineId, Rect<f32, UnknownUnit>),
     /// Requests that the script thread immediately send the constellation the title of a pipeline.