constellation: Proxy ScrollState through the Constellation (#36062)

This will allow removing the dependency of the compositor on
`script_traits`, which should make our internal dependency chain a lot
easier to deal with.

Part of #35984.

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

components/shared/compositing/constellation_msg.rs

@@ -15,7 +15,7 @@ use ipc_channel::ipc::IpcSender;
 use script_traits::{AnimationTickType, LogEntry, WindowSizeData, WindowSizeType};
 use servo_url::ServoUrl;
 use strum_macros::IntoStaticStr;
-use webrender_traits::CompositorHitTestResult;
+use webrender_traits::{CompositorHitTestResult, ScrollState};
 
 /// Messages to the constellation.
 #[derive(IntoStaticStr)]
@@ -69,6 +69,9 @@ pub enum ConstellationMsg {
     MediaSessionAction(MediaSessionActionType),
     /// Set whether to use less resources, by stopping animations and running timers at a heavily limited rate.
     SetWebViewThrottled(WebViewId, bool),
+    /// The Servo renderer scrolled and is updating the scroll states of the nodes in the
+    /// given pipeline via the constellation.
+    SetScrollStates(PipelineId, Vec<ScrollState>),
 }
 
 impl fmt::Debug for ConstellationMsg {

components/shared/script/lib.rs

@@ -33,7 +33,7 @@ use crossbeam_channel::{RecvTimeoutError, Sender};
 use devtools_traits::{DevtoolScriptControlMsg, ScriptToDevtoolsControlMsg, WorkerId};
 use embedder_traits::input_events::InputEvent;
 use embedder_traits::{MediaSessionActionType, Theme, WebDriverScriptCommand};
-use euclid::{Rect, Scale, Size2D, UnknownUnit, Vector2D};
+use euclid::{Rect, Scale, Size2D, UnknownUnit};
 use http::{HeaderMap, Method};
 use ipc_channel::Error as IpcError;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
@@ -56,10 +56,10 @@ use style_traits::{CSSPixel, SpeculativePainter};
 use stylo_atoms::Atom;
 #[cfg(feature = "webgpu")]
 use webgpu::WebGPUMsg;
-use webrender_api::units::{DevicePixel, LayoutPixel};
-use webrender_api::{DocumentId, ExternalScrollId, ImageKey};
+use webrender_api::units::DevicePixel;
+use webrender_api::{DocumentId, ImageKey};
 use webrender_traits::{
-    CompositorHitTestResult, CrossProcessCompositorApi,
+    CompositorHitTestResult, CrossProcessCompositorApi, ScrollState,
     UntrustedNodeAddress as WebRenderUntrustedNodeAddress,
 };
 
@@ -593,15 +593,6 @@ bitflags! {
     }
 }
 
-/// The scroll state of a stacking context.
-#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize)]
-pub struct ScrollState {
-    /// The ID of the scroll root.
-    pub scroll_id: ExternalScrollId,
-    /// The scrolling offset of this stacking context.
-    pub scroll_offset: Vector2D<f32, LayoutPixel>,
-}
-
 /// Data about the window size.
 #[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize)]
 pub struct WindowSizeData {

components/shared/script_layout/lib.rs

@@ -33,7 +33,7 @@ use net_traits::image_cache::{ImageCache, PendingImageId};
 use profile_traits::mem::Report;
 use profile_traits::time;
 use script_traits::{
-    InitialScriptState, LoadData, Painter, ScriptThreadMessage, ScrollState, UntrustedNodeAddress,
+    InitialScriptState, LoadData, Painter, ScriptThreadMessage, UntrustedNodeAddress,
     WindowSizeData,
 };
 use serde::{Deserialize, Serialize};
@@ -53,7 +53,7 @@ use style::selector_parser::{PseudoElement, RestyleDamage, Snapshot};
 use style::stylesheets::Stylesheet;
 use style_traits::CSSPixel;
 use webrender_api::ImageKey;
-use webrender_traits::CrossProcessCompositorApi;
+use webrender_traits::{CrossProcessCompositorApi, ScrollState};
 
 pub type GenericLayoutData = dyn Any + Send + Sync;
 
@@ -243,7 +243,7 @@ pub trait Layout {
     );
 
     /// Set the scroll states of this layout after a compositor scroll.
-    fn set_scroll_states(&mut self, scroll_states: &[ScrollState]);
+    fn set_scroll_offsets(&mut self, scroll_states: &[ScrollState]);
 
     /// Set the paint time for a specific epoch.
     fn set_epoch_paint_time(&mut self, epoch: Epoch, paint_time: CrossProcessInstant);

components/shared/webrender/lib.rs

@@ -14,13 +14,14 @@ use std::sync::{Arc, Mutex};
 use base::id::{PipelineId, WebViewId};
 use display_list::{CompositorDisplayListInfo, ScrollTreeNodeId};
 use embedder_traits::Cursor;
+use euclid::Vector2D;
 use euclid::default::Size2D as UntypedSize2D;
 use ipc_channel::ipc::{self, IpcSender, IpcSharedMemory};
 use libc::c_void;
 use log::warn;
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 use servo_geometry::{DeviceIndependentIntRect, DeviceIndependentIntSize};
-use webrender_api::units::{DevicePoint, LayoutPoint, TexelRect};
+use webrender_api::units::{DevicePoint, LayoutPixel, LayoutPoint, TexelRect};
 use webrender_api::{
     BuiltDisplayList, BuiltDisplayListDescriptor, ExternalImage, ExternalImageData,
     ExternalImageHandler, ExternalImageId, ExternalImageSource, ExternalScrollId,
@@ -530,3 +531,12 @@ pub struct CompositorHitTestResult {
     /// The scroll tree node associated with this hit test item.
     pub scroll_tree_node: ScrollTreeNodeId,
 }
+
+/// The scroll state of a stacking context.
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize)]
+pub struct ScrollState {
+    /// The ID of the scroll root.
+    pub scroll_id: ExternalScrollId,
+    /// The scrolling offset of this stacking context.
+    pub scroll_offset: Vector2D<f32, LayoutPixel>,
+}