Update scroll tree offsets in SetScrollStates

components/compositing/compositor.rs

@@ -698,27 +698,46 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
             ) => {
                 let mut txn = Transaction::new();
                 txn.set_display_list(WebRenderEpoch(0), (pipeline, Default::default()));
-                debug!("INITIAL");
-                self.generate_frame(&mut txn, RenderReasons::APZ);
+                self.generate_frame(&mut txn, RenderReasons::SCENE);
                 self.webrender_api
                     .send_transaction(self.webrender_document, txn);
                 self.webrender_api.flush_scene_builder();
             },
 
             ForwardedToCompositorMsg::Layout(
-                script_traits::ScriptToCompositorMsg::SendScrollNode(point, scroll_id),
+                script_traits::ScriptToCompositorMsg::SendScrollNode(
+                    pipeline_id,
+                    point,
+                    external_scroll_id,
+                ),
             ) => {
+                let pipeline_id = PipelineId::from_webrender(pipeline_id);
+                let pipeline_details = match self.pipeline_details.get_mut(&pipeline_id) {
+                    Some(details) => details,
+                    None => return,
+                };
+
+                let offset = LayoutVector2D::new(point.x, point.y);
+                if !pipeline_details
+                    .scroll_tree
+                    .set_scroll_offsets_for_node_with_external_scroll_id(
+                        external_scroll_id,
+                        -offset,
+                    )
+                {
+                    warn!("Could not scroll not with id: {external_scroll_id:?}");
+                    return;
+                }
+
                 let mut txn = Transaction::new();
-                let offset = point.to_vector();
                 self.webrender_api.flush_scene_builder();
                 txn.set_scroll_offsets(
-                    scroll_id,
+                    external_scroll_id,
                     vec![SampledScrollOffset {
                         offset,
                         generation: 0,
                     }],
                 );
-                debug!("OFFSETS");
                 self.generate_frame(&mut txn, RenderReasons::APZ);
                 self.webrender_api
                     .send_transaction(self.webrender_document, txn);
@@ -787,7 +806,6 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
                         );
                     }
                 }
-                debug!("DISPLAY LIST");
                 self.generate_frame(&mut transaction, RenderReasons::SCENE);
                 self.webrender_api
                     .send_transaction(self.webrender_document, transaction);
@@ -1477,7 +1495,6 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
             self.send_scroll_positions_to_layout_for_pipeline(&pipeline_id);
         }
 
-        debug!("SCROLL ZOOM");
         self.generate_frame(&mut transaction, RenderReasons::APZ);
         self.webrender_api
             .send_transaction(self.webrender_document, transaction);
@@ -2155,7 +2172,6 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
         self.webrender.set_debug_flags(flags);
 
         let mut txn = Transaction::new();
-        debug!("TESTING");
         self.generate_frame(&mut txn, RenderReasons::TESTING);
         self.webrender_api
             .send_transaction(self.webrender_document, txn);

components/layout_thread/lib.rs

@@ -1317,8 +1317,11 @@ impl LayoutThread {
             .insert(state.scroll_id, state.scroll_offset);
 
         let point = Point2D::new(-state.scroll_offset.x, -state.scroll_offset.y);
-        self.webrender_api
-            .send_scroll_node(units::LayoutPoint::from_untyped(point), state.scroll_id);
+        self.webrender_api.send_scroll_node(
+            self.id.to_webrender(),
+            units::LayoutPoint::from_untyped(point),
+            state.scroll_id,
+        );
     }
 
     fn set_scroll_states<'a, 'b>(

components/layout_thread_2020/lib.rs

@@ -984,8 +984,11 @@ impl LayoutThread {
             .insert(state.scroll_id, state.scroll_offset);
 
         let point = Point2D::new(-state.scroll_offset.x, -state.scroll_offset.y);
-        self.webrender_api
-            .send_scroll_node(units::LayoutPoint::from_untyped(point), state.scroll_id);
+        self.webrender_api.send_scroll_node(
+            self.id.to_webrender(),
+            units::LayoutPoint::from_untyped(point),
+            state.scroll_id,
+        );
     }
 
     fn set_scroll_states<'a, 'b>(

components/shared/script/compositor.rs

@@ -216,6 +216,25 @@ impl ScrollTree {
 
         parent.and_then(|parent| self.scroll_node_or_ancestor(&parent, scroll_location))
     }
+
+    /// Given an [`ExternalScrollId`] and an offset, update the scroll offset of the scroll node
+    /// with the given id.
+    pub fn set_scroll_offsets_for_node_with_external_scroll_id(
+        &mut self,
+        external_scroll_id: ExternalScrollId,
+        offset: LayoutVector2D,
+    ) -> bool {
+        for node in self.nodes.iter_mut() {
+            match node.scroll_info {
+                Some(ref mut scroll_info) if scroll_info.external_id == external_scroll_id => {
+                    scroll_info.offset = offset;
+                    return true;
+                },
+                _ => {},
+            }
+        }
+        false
+    }
 }
 
 /// A data structure which stores compositor-side information about

components/shared/script/lib.rs

@@ -1121,7 +1121,7 @@ pub enum ScriptToCompositorMsg {
     /// Inform WebRender of the existence of this pipeline.
     SendInitialTransaction(WebRenderPipelineId),
     /// Perform a scroll operation.
-    SendScrollNode(LayoutPoint, ExternalScrollId),
+    SendScrollNode(WebRenderPipelineId, LayoutPoint, ExternalScrollId),
     /// Inform WebRender of a new display list for the given pipeline.
     SendDisplayList {
         /// The [CompositorDisplayListInfo] that describes the display list being sent.
@@ -1167,11 +1167,17 @@ impl WebrenderIpcSender {
     }
 
     /// Perform a scroll operation.
-    pub fn send_scroll_node(&self, point: LayoutPoint, scroll_id: ExternalScrollId) {
-        if let Err(e) = self
-            .0
-            .send(ScriptToCompositorMsg::SendScrollNode(point, scroll_id))
-        {
+    pub fn send_scroll_node(
+        &self,
+        pipeline_id: WebRenderPipelineId,
+        point: LayoutPoint,
+        scroll_id: ExternalScrollId,
+    ) {
+        if let Err(e) = self.0.send(ScriptToCompositorMsg::SendScrollNode(
+            pipeline_id,
+            point,
+            scroll_id,
+        )) {
             warn!("Error sending scroll node: {}", e);
         }
     }