layout: Measure stacking context tree in layout thread memory report (#38762)

Measures the memory usage of the stacking context tree in the memory
report of the layout thread by adding `MallocSizeOf` to
`StackingContextTree` and all the types required for that. Also requires
adding `MallocSizeOf` to some webrender types.

Testing: Manually looked at about:memory
<img width="636" height="241" alt="image"
src="https://github.com/user-attachments/assets/6bf9d65a-0bf0-4a99-99b5-ddedba3269c1"
/>

Fixes: https://github.com/servo/servo/issues/38725

---------

Signed-off-by: Rahul Menon <menonrahul02@gmail.com>

Cargo.lock

@@ -6219,7 +6219,7 @@ dependencies = [
 [[package]]
 name = "peek-poke"
 version = "0.3.0"
-source = "git+https://github.com/servo/webrender?branch=0.67#15318d6627e91ec19fc0a44a7434b08673413140"
+source = "git+https://github.com/servo/webrender?branch=0.67#428d64dc5c92f157be2b0fd85dc7a6506be77132"
 dependencies = [
  "euclid",
  "peek-poke-derive",
@@ -6228,7 +6228,7 @@ dependencies = [
 [[package]]
 name = "peek-poke-derive"
 version = "0.3.0"
-source = "git+https://github.com/servo/webrender?branch=0.67#15318d6627e91ec19fc0a44a7434b08673413140"
+source = "git+https://github.com/servo/webrender?branch=0.67#428d64dc5c92f157be2b0fd85dc7a6506be77132"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -7751,6 +7751,7 @@ dependencies = [
  "url",
  "urlpattern",
  "uuid",
+ "webrender",
  "webrender_api",
  "wr_malloc_size_of",
 ]
@@ -9687,7 +9688,7 @@ dependencies = [
 [[package]]
 name = "webrender"
 version = "0.66.0"
-source = "git+https://github.com/servo/webrender?branch=0.67#15318d6627e91ec19fc0a44a7434b08673413140"
+source = "git+https://github.com/servo/webrender?branch=0.67#428d64dc5c92f157be2b0fd85dc7a6506be77132"
 dependencies = [
  "allocator-api2",
  "bincode",
@@ -9722,7 +9723,7 @@ dependencies = [
 [[package]]
 name = "webrender_api"
 version = "0.66.0"
-source = "git+https://github.com/servo/webrender?branch=0.67#15318d6627e91ec19fc0a44a7434b08673413140"
+source = "git+https://github.com/servo/webrender?branch=0.67#428d64dc5c92f157be2b0fd85dc7a6506be77132"
 dependencies = [
  "app_units",
  "bitflags 2.9.2",
@@ -9743,7 +9744,7 @@ dependencies = [
 [[package]]
 name = "webrender_build"
 version = "0.0.2"
-source = "git+https://github.com/servo/webrender?branch=0.67#15318d6627e91ec19fc0a44a7434b08673413140"
+source = "git+https://github.com/servo/webrender?branch=0.67#428d64dc5c92f157be2b0fd85dc7a6506be77132"
 dependencies = [
  "bitflags 2.9.2",
  "lazy_static",
@@ -10455,7 +10456,7 @@ dependencies = [
 [[package]]
 name = "wr_glyph_rasterizer"
 version = "0.1.0"
-source = "git+https://github.com/servo/webrender?branch=0.67#15318d6627e91ec19fc0a44a7434b08673413140"
+source = "git+https://github.com/servo/webrender?branch=0.67#428d64dc5c92f157be2b0fd85dc7a6506be77132"
 dependencies = [
  "core-foundation 0.9.4",
  "core-graphics",
@@ -10480,7 +10481,7 @@ dependencies = [
 [[package]]
 name = "wr_malloc_size_of"
 version = "0.2.0"
-source = "git+https://github.com/servo/webrender?branch=0.67#15318d6627e91ec19fc0a44a7434b08673413140"
+source = "git+https://github.com/servo/webrender?branch=0.67#428d64dc5c92f157be2b0fd85dc7a6506be77132"
 dependencies = [
  "app_units",
  "euclid",

components/layout/display_list/clip.rs

@@ -4,6 +4,7 @@
 
 use app_units::Au;
 use base::id::ScrollTreeNodeId;
+use malloc_size_of_derive::MallocSizeOf;
 use style::values::computed::basic_shape::{BasicShape, ClipPath};
 use style::values::computed::length_percentage::NonNegativeLengthPercentage;
 use style::values::computed::position::Position;
@@ -16,7 +17,7 @@ use super::{BuilderForBoxFragment, compute_margin_box_radius, normalize_radii};
 
 /// An identifier for a clip used during StackingContextTree construction. This is a simple index in
 /// a [`ClipStore`]s vector of clips.
-#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+#[derive(Clone, Copy, Debug, Eq, Hash, MallocSizeOf, PartialEq)]
 pub(crate) struct ClipId(pub usize);
 
 impl ClipId {
@@ -27,7 +28,7 @@ impl ClipId {
 /// All the information needed to create a clip on a WebRender display list. These are created at
 /// two times: during `StackingContextTree` creation and during WebRender display list construction.
 /// Only the former are stored in a [`ClipStore`].
-#[derive(Clone)]
+#[derive(Clone, MallocSizeOf)]
 pub(crate) struct Clip {
     pub id: ClipId,
     pub radii: BorderRadius,
@@ -39,7 +40,7 @@ pub(crate) struct Clip {
 /// A simple vector of [`Clip`] that is built during `StackingContextTree` construction.
 /// These are later turned into WebRender clips and clip chains during WebRender display
 /// list construction.
-#[derive(Clone, Default)]
+#[derive(Clone, Default, MallocSizeOf)]
 pub(crate) struct StackingContextTreeClipStore(pub Vec<Clip>);
 
 impl StackingContextTreeClipStore {

components/layout/display_list/stacking_context.rs

@@ -18,6 +18,7 @@ use embedder_traits::ViewportDetails;
 use euclid::SideOffsets2D;
 use euclid::default::{Point2D, Rect, Size2D};
 use log::warn;
+use malloc_size_of_derive::MallocSizeOf;
 use servo_config::opts::DebugOptions;
 use style::Zero;
 use style::color::AbsoluteColor;
@@ -92,7 +93,7 @@ impl ContainingBlock {
 
 pub(crate) type ContainingBlockInfo<'a> = ContainingBlockManager<'a, ContainingBlock>;
 
-#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
+#[derive(Clone, Copy, Debug, Eq, Ord, MallocSizeOf, PartialEq, PartialOrd)]
 pub(crate) enum StackingContextSection {
     OwnBackgroundsAndBorders,
     DescendantBackgroundsAndBorders,
@@ -100,6 +101,7 @@ pub(crate) enum StackingContextSection {
     Outline,
 }
 
+#[derive(MallocSizeOf)]
 pub(crate) struct ScrollFrameHitTestItem {
     /// The [`ScrollTreeNodeId`] of the spatial node that contains this hit test item.
     pub scroll_node_id: ScrollTreeNodeId,
@@ -116,6 +118,7 @@ pub(crate) struct ScrollFrameHitTestItem {
     pub external_scroll_id: ExternalScrollId,
 }
 
+#[derive(MallocSizeOf)]
 pub(crate) struct StackingContextTree {
     /// The root stacking context of this [`StackingContextTree`].
     pub root_stacking_context: StackingContext,
@@ -282,7 +285,7 @@ impl StackingContextTree {
 }
 
 /// The text decorations for a Fragment, collecting during [`StackingContextTree`] construction.
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, MallocSizeOf)]
 pub(crate) struct FragmentTextDecoration {
     pub line: TextDecorationLine,
     pub color: AbsoluteColor,
@@ -293,6 +296,7 @@ pub(crate) struct FragmentTextDecoration {
 ///
 /// This is generally part of a fragment, like its borders or foreground, but it
 /// can also be a stacking container that needs to be painted in fragment order.
+#[derive(MallocSizeOf)]
 pub(crate) enum StackingContextContent {
     /// A fragment that does not generate a stacking context or stacking container.
     Fragment {
@@ -303,6 +307,7 @@ pub(crate) enum StackingContextContent {
         containing_block: PhysicalRect<Au>,
         fragment: Fragment,
         is_collapsed_table_borders: bool,
+        #[conditional_malloc_size_of]
         text_decorations: Arc<Vec<FragmentTextDecoration>>,
     },
 
@@ -354,7 +359,7 @@ impl StackingContextContent {
     }
 }
 
-#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq)]
 pub(crate) enum StackingContextType {
     RealStackingContext,
     PositionedStackingContainer,
@@ -367,6 +372,7 @@ pub(crate) enum StackingContextType {
 ///
 /// We use the term “real stacking context” in situations that call for a
 /// stacking context but not a stacking container.
+#[derive(MallocSizeOf)]
 pub struct StackingContext {
     /// The spatial id of this fragment. This is used to properly handle
     /// things like preserve-3d.
@@ -416,14 +422,14 @@ pub struct StackingContext {
 }
 
 /// Refers to one of the child contents or stacking contexts of a [StackingContext].
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, MallocSizeOf)]
 pub struct DebugPrintItem {
     field: DebugPrintField,
     index: usize,
 }
 
 /// Refers to one of the vecs of a [StackingContext].
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, MallocSizeOf)]
 pub enum DebugPrintField {
     Contents,
     RealStackingContextsAndPositionedStackingContainers,

components/layout/layout_impl.rs

@@ -459,6 +459,12 @@ impl Layout for LayoutThread {
                 .unwrap_or_default(),
         });
 
+        reports.push(Report {
+            path: path![formatted_url, "layout-thread", "stacking-context-tree"],
+            kind: ReportKind::ExplicitJemallocHeapSize,
+            size: self.stacking_context_tree.size_of(ops),
+        });
+
         reports.push(self.image_cache.memory_report(formatted_url, ops));
     }
 

components/malloc_size_of/Cargo.toml

@@ -39,5 +39,6 @@ unicode-script = { workspace = true }
 url = { workspace = true }
 urlpattern = { workspace = true }
 uuid = { workspace = true }
+webrender = { workspace = true }
 webrender_api = { workspace = true }
 wr_malloc_size_of = { workspace = true }

components/malloc_size_of/lib.rs

@@ -643,6 +643,12 @@ impl<T: MallocSizeOf, U> MallocSizeOf for euclid::Point2D<T, U> {
     }
 }
 
+impl<T: MallocSizeOf, U> MallocSizeOf for euclid::Box2D<T, U> {
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        self.min.size_of(ops) + self.max.size_of(ops)
+    }
+}
+
 impl<T: MallocSizeOf, U> MallocSizeOf for euclid::Rect<T, U> {
     fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
         self.origin.size_of(ops) + self.size.size_of(ops)
@@ -826,7 +832,9 @@ malloc_size_of_is_webrender_malloc_size_of!(webrender_api::BorderRadius);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::BorderStyle);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::BoxShadowClipMode);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::ColorF);
+malloc_size_of_is_webrender_malloc_size_of!(webrender_api::Epoch);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::ExtendMode);
+malloc_size_of_is_webrender_malloc_size_of!(webrender_api::ExternalScrollId);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::FontKey);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::FontInstanceKey);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::GlyphInstance);
@@ -836,8 +844,14 @@ malloc_size_of_is_webrender_malloc_size_of!(webrender_api::ImageRendering);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::LineStyle);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::MixBlendMode);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::NormalBorder);
+malloc_size_of_is_webrender_malloc_size_of!(webrender_api::PipelineId);
+malloc_size_of_is_webrender_malloc_size_of!(webrender_api::ReferenceFrameKind);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::RepeatMode);
 malloc_size_of_is_webrender_malloc_size_of!(webrender_api::FontVariation);
+malloc_size_of_is_webrender_malloc_size_of!(webrender_api::SpatialId);
+malloc_size_of_is_webrender_malloc_size_of!(webrender_api::StickyOffsetBounds);
+malloc_size_of_is_webrender_malloc_size_of!(webrender_api::TransformStyle);
+malloc_size_of_is_webrender_malloc_size_of!(webrender::FastTransform<webrender_api::units::LayoutPixel,webrender_api::units::LayoutPixel>);
 
 macro_rules! malloc_size_of_is_stylo_malloc_size_of(
     ($($ty:ty),+) => (
@@ -892,6 +906,7 @@ malloc_size_of_is_stylo_malloc_size_of!(style::attr::AttrIdentifier);
 malloc_size_of_is_stylo_malloc_size_of!(style::attr::AttrValue);
 malloc_size_of_is_stylo_malloc_size_of!(style::color::AbsoluteColor);
 malloc_size_of_is_stylo_malloc_size_of!(style::computed_values::font_variant_caps::T);
+malloc_size_of_is_stylo_malloc_size_of!(style::computed_values::text_decoration_style::T);
 malloc_size_of_is_stylo_malloc_size_of!(style::dom::OpaqueNode);
 malloc_size_of_is_stylo_malloc_size_of!(style::invalidation::element::restyle_hints::RestyleHint);
 malloc_size_of_is_stylo_malloc_size_of!(style::logical_geometry::WritingMode);

components/shared/compositing/display_list.rs

@@ -56,14 +56,14 @@ pub struct AxesScrollSensitivity {
     pub y: ScrollType,
 }
 
-#[derive(Debug, Deserialize, Serialize)]
+#[derive(Debug, Deserialize, MallocSizeOf, Serialize)]
 pub enum SpatialTreeNodeInfo {
     ReferenceFrame(ReferenceFrameNodeInfo),
     Scroll(ScrollableNodeInfo),
     Sticky(StickyNodeInfo),
 }
 
-#[derive(Debug, Deserialize, Serialize)]
+#[derive(Debug, Deserialize, MallocSizeOf, Serialize)]
 pub struct StickyNodeInfo {
     pub frame_rect: LayoutRect,
     pub margins: SideOffsets2D<Option<f32>, LayoutPixel>,
@@ -160,7 +160,7 @@ impl StickyNodeInfo {
     }
 }
 
-#[derive(Debug, Deserialize, Serialize)]
+#[derive(Debug, Deserialize, MallocSizeOf, Serialize)]
 pub struct ReferenceFrameNodeInfo {
     pub origin: LayoutPoint,
     /// Origin of this frame relative to the document for bounding box queries.
@@ -172,7 +172,7 @@ pub struct ReferenceFrameNodeInfo {
 
 /// Data stored for nodes in the [ScrollTree] that actually scroll,
 /// as opposed to reference frames and sticky nodes which do not.
-#[derive(Debug, Deserialize, Serialize)]
+#[derive(Debug, Deserialize, MallocSizeOf, Serialize)]
 pub struct ScrollableNodeInfo {
     /// The external scroll id of this node, used to track
     /// it between successive re-layouts.
@@ -278,7 +278,7 @@ impl ScrollableNodeInfo {
 /// Potential ideas for improvement:
 ///  - Test optimizing simple translations to avoid having to do full matrix
 ///    multiplication when transforms are not involved.
-#[derive(Clone, Copy, Debug, Default, Deserialize, Serialize)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, MallocSizeOf, Serialize)]
 pub struct ScrollTreeNodeTransformationCache {
     node_to_root_transform: FastLayoutTransform,
     root_to_node_transform: Option<FastLayoutTransform>,
@@ -290,7 +290,7 @@ struct AncestorStickyInfo {
     nearest_scrolling_ancestor_viewport: LayoutRect,
 }
 
-#[derive(Debug, Deserialize, Serialize)]
+#[derive(Debug, Deserialize, MallocSizeOf, Serialize)]
 /// A node in a tree of scroll nodes. This may either be a scrollable
 /// node which responds to scroll events or a non-scrollable one.
 pub struct ScrollTreeNode {
@@ -421,7 +421,7 @@ impl ScrollTreeNode {
 /// A tree of spatial nodes, which mirrors the spatial nodes in the WebRender
 /// display list, except these are used to scrolling in the compositor so that
 /// new offsets can be sent to WebRender.
-#[derive(Debug, Default, Deserialize, Serialize)]
+#[derive(Debug, Default, Deserialize, MallocSizeOf, Serialize)]
 pub struct ScrollTree {
     /// A list of compositor-side scroll nodes that describe the tree
     /// of WebRender spatial nodes, used by the compositor to scroll the
@@ -778,7 +778,7 @@ impl ScrollTree {
 
 /// A data structure which stores compositor-side information about
 /// display lists sent to the compositor.
-#[derive(Debug, Deserialize, Serialize)]
+#[derive(Debug, Deserialize, MallocSizeOf, Serialize)]
 pub struct CompositorDisplayListInfo {
     /// The WebRender [PipelineId] of this display list.
     pub pipeline_id: PipelineId,