Scroll from script should trigger a reflow

Scrolling from script should flow layout and send a display list to WebRender. This allows all of the scroll nodes to exist in WebRender before asking it to move the node. See https://gist.github.com/paulirish/5d52fb081b3570c81e3a. Fixes #29659.
2025-08-05 05:30:08 +01:00 · 2023-04-25 08:29:09 +02:00 · 2023-04-25 08:29:09 +02:00 · 3ab5e2a188
commit 3ab5e2a188
parent 2ae158dec1
25 changed files with 161 additions and 188 deletions
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@ -645,9 +645,6 @@ impl LayoutThread {
            Msg::CreateLayoutThread(..) => LayoutHangAnnotation::CreateLayoutThread,
            Msg::SetFinalUrl(..) => LayoutHangAnnotation::SetFinalUrl,
            Msg::SetScrollStates(..) => LayoutHangAnnotation::SetScrollStates,
-            Msg::UpdateScrollStateFromScript(..) => {
-                LayoutHangAnnotation::UpdateScrollStateFromScript
-            },
            Msg::RegisterPaint(..) => LayoutHangAnnotation::RegisterPaint,
            Msg::SetNavigationStart(..) => LayoutHangAnnotation::SetNavigationStart,
        };
@ -753,19 +750,6 @@ impl LayoutThread {
            Msg::SetScrollStates(new_scroll_states) => {
                self.set_scroll_states(new_scroll_states, possibly_locked_rw_data);
            },
-            Msg::UpdateScrollStateFromScript(state) => {
-                let mut rw_data = possibly_locked_rw_data.lock();
-                rw_data
-                    .scroll_offsets
-                    .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(
-                    webrender_api::units::LayoutPoint::from_untyped(point),
-                    state.scroll_id,
-                    webrender_api::ScrollClamping::ToContentBounds,
-                );
-            },
            Msg::CollectReports(reports_chan) => {
                self.collect_reports(reports_chan, possibly_locked_rw_data);
            },
@ -1250,7 +1234,9 @@ impl LayoutThread {
                            rw_data.inner_window_dimensions_response = None;
                        },
                    },
-                    ReflowGoal::Full | ReflowGoal::TickAnimations => {},
+                    ReflowGoal::Full |
+                    ReflowGoal::TickAnimations |
+                    ReflowGoal::UpdateScrollNode(_) => {},
                }
                return;
            },
@ -1619,10 +1605,26 @@ impl LayoutThread {
                        .cloned();
                },
            },
+            ReflowGoal::UpdateScrollNode(scroll_state) => {
+                self.update_scroll_node_state(&scroll_state, rw_data);
+            },
            ReflowGoal::Full | ReflowGoal::TickAnimations => {},
        }
    }

+    fn update_scroll_node_state(&self, state: &ScrollState, rw_data: &mut LayoutThreadData) {
+        rw_data
+            .scroll_offsets
+            .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(
+            webrender_api::units::LayoutPoint::from_untyped(point),
+            state.scroll_id,
+            webrender_api::ScrollClamping::ToContentBounds,
+        );
+    }
+
    fn set_scroll_states<'a, 'b>(
        &mut self,
        new_scroll_states: Vec<ScrollState>,
--- a/components/layout_thread_2020/lib.rs
+++ b/components/layout_thread_2020/lib.rs
@ -616,9 +616,6 @@ impl LayoutThread {
            Msg::CreateLayoutThread(..) => LayoutHangAnnotation::CreateLayoutThread,
            Msg::SetFinalUrl(..) => LayoutHangAnnotation::SetFinalUrl,
            Msg::SetScrollStates(..) => LayoutHangAnnotation::SetScrollStates,
-            Msg::UpdateScrollStateFromScript(..) => {
-                LayoutHangAnnotation::UpdateScrollStateFromScript
-            },
            Msg::RegisterPaint(..) => LayoutHangAnnotation::RegisterPaint,
            Msg::SetNavigationStart(..) => LayoutHangAnnotation::SetNavigationStart,
        };
@ -724,19 +721,6 @@ impl LayoutThread {
            Msg::SetScrollStates(new_scroll_states) => {
                self.set_scroll_states(new_scroll_states, possibly_locked_rw_data);
            },
-            Msg::UpdateScrollStateFromScript(state) => {
-                let mut rw_data = possibly_locked_rw_data.lock();
-                rw_data
-                    .scroll_offsets
-                    .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(
-                    webrender_api::units::LayoutPoint::from_untyped(point),
-                    state.scroll_id,
-                    webrender_api::ScrollClamping::ToContentBounds,
-                );
-            },
            Msg::CollectReports(reports_chan) => {
                self.collect_reports(reports_chan, possibly_locked_rw_data);
            },
@ -935,7 +919,9 @@ impl LayoutThread {
                                .cloned();
                        },
                    },
-                    ReflowGoal::Full | ReflowGoal::TickAnimations => {},
+                    ReflowGoal::Full |
+                    ReflowGoal::TickAnimations |
+                    ReflowGoal::UpdateScrollNode(_) => {},
                }
                return;
            },
@ -1256,10 +1242,26 @@ impl LayoutThread {
                    rw_data.inner_window_dimensions_response = None;
                },
            },
+            ReflowGoal::UpdateScrollNode(scroll_state) => {
+                self.update_scroll_node_state(&scroll_state, rw_data);
+            },
            ReflowGoal::Full | ReflowGoal::TickAnimations => {},
        }
    }

+    fn update_scroll_node_state(&self, state: &ScrollState, rw_data: &mut LayoutThreadData) {
+        rw_data
+            .scroll_offsets
+            .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(
+            webrender_api::units::LayoutPoint::from_untyped(point),
+            state.scroll_id,
+            webrender_api::ScrollClamping::ToContentBounds,
+        );
+    }
+
    fn set_scroll_states<'a, 'b>(
        &mut self,
        new_scroll_states: Vec<ScrollState>,
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@ -168,26 +168,27 @@ enum WindowState {
 #[derive(Debug, MallocSizeOf)]
 pub enum ReflowReason {
    CachedPageNeededReflow,
-    RefreshTick,
-    FirstLoad,
-    KeyEvent,
-    MouseEvent,
-    Query,
-    Timer,
-    Viewport,
-    WindowResize,
    DOMContentLoaded,
    DocumentLoaded,
-    StylesheetLoaded,
-    ImageLoaded,
-    RequestAnimationFrame,
-    WebFontLoaded,
-    WorkletLoaded,
+    ElementStateChanged,
+    FirstLoad,
    FramedContentChanged,
    IFrameLoadEvent,
+    ImageLoaded,
+    KeyEvent,
    MissingExplicitReflow,
-    ElementStateChanged,
+    MouseEvent,
    PendingReflow,
+    Query,
+    RefreshTick,
+    RequestAnimationFrame,
+    ScrollFromScript,
+    StylesheetLoaded,
+    Timer,
+    Viewport,
+    WebFontLoaded,
+    WindowResize,
+    WorkletLoaded,
 }

 #[dom_struct]
@ -1755,15 +1756,13 @@ impl Window {
        // TODO Step 1
        // TODO(mrobinson, #18709): Add smooth scrolling support to WebRender so that we can
        // properly process ScrollBehavior here.
-        match self.layout_chan() {
-            Some(chan) => chan
-                .send(Msg::UpdateScrollStateFromScript(ScrollState {
-                    scroll_id,
-                    scroll_offset: Vector2D::new(-x, -y),
-                }))
-                .unwrap(),
-            None => warn!("Layout channel unavailable"),
-        }
+        self.reflow(
+            ReflowGoal::UpdateScrollNode(ScrollState {
+                scroll_id,
+                scroll_offset: Vector2D::new(-x, -y),
+            }),
+            ReflowReason::ScrollFromScript,
+        );
    }

    pub fn update_viewport_for_scroll(&self, x: f32, y: f32) {
@ -2719,6 +2718,7 @@ fn debug_reflow_events(id: PipelineId, reflow_goal: &ReflowGoal, reason: &Reflow
    let goal_string = match *reflow_goal {
        ReflowGoal::Full => "\tFull",
        ReflowGoal::TickAnimations => "\tTickAnimations",
+        ReflowGoal::UpdateScrollNode(_) => "\tUpdateScrollNode",
        ReflowGoal::LayoutQuery(ref query_msg, _) => match query_msg {
            &QueryMsg::ContentBoxQuery(_n) => "\tContentBoxQuery",
            &QueryMsg::ContentBoxesQuery(_n) => "\tContentBoxesQuery",
--- a/components/script_layout_interface/message.rs
+++ b/components/script_layout_interface/message.rs
@ -81,10 +81,6 @@ pub enum Msg {
    /// Tells layout about the new scrolling offsets of each scrollable stacking context.
    SetScrollStates(Vec<ScrollState>),

-    /// Tells layout about a single new scrolling offset from the script. The rest will
-    /// remain untouched and layout won't forward this back to script.
-    UpdateScrollStateFromScript(ScrollState),
-
    /// Tells layout that script has added some paint worklet modules.
    RegisterPaint(Atom, Vec<Atom>, Box<dyn Painter>),

@ -125,6 +121,10 @@ pub enum ReflowGoal {
    Full,
    TickAnimations,
    LayoutQuery(QueryMsg, u64),
+
+    /// Tells layout about a single new scrolling offset from the script. The rest will
+    /// remain untouched and layout won't forward this back to script.
+    UpdateScrollNode(ScrollState),
 }

 impl ReflowGoal {
@ -132,7 +132,7 @@ impl ReflowGoal {
    /// be present or false if it only needs stacking-relative positions.
    pub fn needs_display_list(&self) -> bool {
        match *self {
-            ReflowGoal::Full | ReflowGoal::TickAnimations => true,
+            ReflowGoal::Full | ReflowGoal::TickAnimations | ReflowGoal::UpdateScrollNode(_) => true,
            ReflowGoal::LayoutQuery(ref querymsg, _) => match *querymsg {
                QueryMsg::NodesFromPointQuery(..) |
                QueryMsg::TextIndexQuery(..) |
@ -155,7 +155,7 @@ impl ReflowGoal {
    /// false if a layout_thread display list is sufficient.
    pub fn needs_display(&self) -> bool {
        match *self {
-            ReflowGoal::Full | ReflowGoal::TickAnimations => true,
+            ReflowGoal::Full | ReflowGoal::TickAnimations | ReflowGoal::UpdateScrollNode(_) => true,
            ReflowGoal::LayoutQuery(ref querymsg, _) => match *querymsg {
                QueryMsg::NodesFromPointQuery(..) |
                QueryMsg::TextIndexQuery(..) |
--- a/components/script_traits/lib.rs
+++ b/components/script_traits/lib.rs
@ -791,7 +791,7 @@ bitflags! {
 }

 /// The scroll state of a stacking context.
-#[derive(Clone, Copy, Debug, Deserialize, Serialize)]
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize)]
 pub struct ScrollState {
    /// The ID of the scroll root.
    pub scroll_id: ExternalScrollId,