servo/components/layout/dom.rs
Martin Robinson 51367c22a6
layout: Store most anonymous pseudo-elements in box slots (#37941)
Previously, anonymous boxes, such for anonymous table parts were not
associated with their non-pseudo ancestor DOM nodes. This presents a
problem when it comes time to clear layout data during incremental
layouts. This change reworks the way that pseudo-elements in general are
stored in their non-pseudo ancestor DOM nodes, allowing for any number
to be placed there.

This trades a bit of performance for space, as just adding a vector to
the node would add something like 24 bytes of storage to every node.
This change should have a neutral runtime memory usage.

Testing: This shouldn't change observable behavior and is thus covered
by
existing WPT tests. It will allow tests to pass in a subsequent PR.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>
2025-07-08 15:22:09 +00:00

433 lines
15 KiB
Rust
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
use std::any::Any;
use std::marker::PhantomData;
use atomic_refcell::{AtomicRef, AtomicRefCell, AtomicRefMut};
use base::id::{BrowsingContextId, PipelineId};
use html5ever::{local_name, ns};
use layout_api::wrapper_traits::{
LayoutDataTrait, LayoutNode, ThreadSafeLayoutElement, ThreadSafeLayoutNode,
};
use layout_api::{
GenericLayoutDataTrait, LayoutDamage, LayoutElementType, LayoutNodeType as ScriptLayoutNodeType,
};
use malloc_size_of_derive::MallocSizeOf;
use net_traits::image_cache::Image;
use script::layout_dom::ServoLayoutNode;
use servo_arc::Arc as ServoArc;
use smallvec::SmallVec;
use style::context::SharedStyleContext;
use style::properties::ComputedValues;
use style::selector_parser::{PseudoElement, RestyleDamage};
use crate::cell::ArcRefCell;
use crate::flexbox::FlexLevelBox;
use crate::flow::BlockLevelBox;
use crate::flow::inline::{InlineItem, SharedInlineStyles};
use crate::fragment_tree::Fragment;
use crate::geom::PhysicalSize;
use crate::replaced::CanvasInfo;
use crate::table::TableLevelBox;
use crate::taffy::TaffyItemBox;
#[derive(MallocSizeOf)]
pub struct PseudoLayoutData {
pseudo: PseudoElement,
box_slot: ArcRefCell<Option<LayoutBox>>,
}
/// The data that is stored in each DOM node that is used by layout.
#[derive(Default, MallocSizeOf)]
pub struct InnerDOMLayoutData {
pub(super) self_box: ArcRefCell<Option<LayoutBox>>,
pub(super) pseudo_boxes: SmallVec<[PseudoLayoutData; 2]>,
}
impl InnerDOMLayoutData {
pub(crate) fn for_pseudo(
&self,
pseudo_element: Option<PseudoElement>,
) -> Option<AtomicRef<Option<LayoutBox>>> {
let Some(pseudo_element) = pseudo_element else {
return Some(self.self_box.borrow());
};
for pseudo_layout_data in self.pseudo_boxes.iter() {
if pseudo_element == pseudo_layout_data.pseudo {
return Some(pseudo_layout_data.box_slot.borrow());
}
}
None
}
}
/// A box that is stored in one of the `DOMLayoutData` slots.
#[derive(MallocSizeOf)]
pub(super) enum LayoutBox {
DisplayContents(SharedInlineStyles),
BlockLevel(ArcRefCell<BlockLevelBox>),
InlineLevel(Vec<ArcRefCell<InlineItem>>),
FlexLevel(ArcRefCell<FlexLevelBox>),
TableLevelBox(TableLevelBox),
TaffyItemBox(ArcRefCell<TaffyItemBox>),
}
impl LayoutBox {
fn invalidate_cached_fragment(&self) {
match self {
LayoutBox::DisplayContents(..) => {},
LayoutBox::BlockLevel(block_level_box) => {
block_level_box.borrow().invalidate_cached_fragment()
},
LayoutBox::InlineLevel(inline_items) => {
for inline_item in inline_items.iter() {
inline_item.borrow().invalidate_cached_fragment()
}
},
LayoutBox::FlexLevel(flex_level_box) => {
flex_level_box.borrow().invalidate_cached_fragment()
},
LayoutBox::TaffyItemBox(taffy_item_box) => {
taffy_item_box.borrow_mut().invalidate_cached_fragment()
},
LayoutBox::TableLevelBox(table_box) => table_box.invalidate_cached_fragment(),
}
}
pub(crate) fn fragments(&self) -> Vec<Fragment> {
match self {
LayoutBox::DisplayContents(..) => vec![],
LayoutBox::BlockLevel(block_level_box) => block_level_box.borrow().fragments(),
LayoutBox::InlineLevel(inline_items) => inline_items
.iter()
.flat_map(|inline_item| inline_item.borrow().fragments())
.collect(),
LayoutBox::FlexLevel(flex_level_box) => flex_level_box.borrow().fragments(),
LayoutBox::TaffyItemBox(taffy_item_box) => taffy_item_box.borrow().fragments(),
LayoutBox::TableLevelBox(table_box) => table_box.fragments(),
}
}
fn repair_style(
&self,
context: &SharedStyleContext,
node: &ServoLayoutNode,
new_style: &ServoArc<ComputedValues>,
) {
match self {
LayoutBox::DisplayContents(inline_shared_styles) => {
*inline_shared_styles.style.borrow_mut() = new_style.clone();
*inline_shared_styles.selected.borrow_mut() = node.to_threadsafe().selected_style();
},
LayoutBox::BlockLevel(block_level_box) => {
block_level_box
.borrow_mut()
.repair_style(context, node, new_style);
},
LayoutBox::InlineLevel(inline_items) => {
for inline_item in inline_items {
inline_item
.borrow_mut()
.repair_style(context, node, new_style);
}
},
LayoutBox::FlexLevel(flex_level_box) => flex_level_box
.borrow_mut()
.repair_style(context, node, new_style),
LayoutBox::TableLevelBox(table_level_box) => {
table_level_box.repair_style(context, node, new_style)
},
LayoutBox::TaffyItemBox(taffy_item_box) => taffy_item_box
.borrow_mut()
.repair_style(context, node, new_style),
}
}
/// If this [`LayoutBox`] represents an unsplit (due to inline-block splits) inline
/// level item, unwrap and return it. If not, return `None`.
pub(crate) fn unsplit_inline_level_layout_box(self) -> Option<ArcRefCell<InlineItem>> {
let LayoutBox::InlineLevel(inline_level_boxes) = self else {
return None;
};
// If this element box has been subject to inline-block splitting, ignore it. It's
// not useful currently for incremental box tree construction.
if inline_level_boxes.len() != 1 {
return None;
}
inline_level_boxes.into_iter().next()
}
}
/// A wrapper for [`InnerDOMLayoutData`]. This is necessary to give the entire data
/// structure interior mutability, as we will need to mutate the layout data of
/// non-mutable DOM nodes.
#[derive(Default, MallocSizeOf)]
pub struct DOMLayoutData(AtomicRefCell<InnerDOMLayoutData>);
// The implementation of this trait allows the data to be stored in the DOM.
impl LayoutDataTrait for DOMLayoutData {}
impl GenericLayoutDataTrait for DOMLayoutData {
fn as_any(&self) -> &dyn Any {
self
}
}
pub struct BoxSlot<'dom> {
pub(crate) slot: Option<ArcRefCell<Option<LayoutBox>>>,
pub(crate) marker: PhantomData<&'dom ()>,
}
impl From<ArcRefCell<Option<LayoutBox>>> for BoxSlot<'_> {
fn from(layout_box_slot: ArcRefCell<Option<LayoutBox>>) -> Self {
let slot = Some(layout_box_slot);
Self {
slot,
marker: PhantomData,
}
}
}
/// A mutable reference to a `LayoutBox` stored in a DOM element.
impl BoxSlot<'_> {
pub(crate) fn dummy() -> Self {
let slot = None;
Self {
slot,
marker: PhantomData,
}
}
pub(crate) fn set(mut self, box_: LayoutBox) {
if let Some(slot) = &mut self.slot {
*slot.borrow_mut() = Some(box_);
}
}
pub(crate) fn take_layout_box_if_undamaged(&self, damage: LayoutDamage) -> Option<LayoutBox> {
if damage.has_box_damage() {
return None;
}
self.slot.as_ref().and_then(|slot| slot.borrow_mut().take())
}
}
impl Drop for BoxSlot<'_> {
fn drop(&mut self) {
if !std::thread::panicking() {
if let Some(slot) = &mut self.slot {
assert!(slot.borrow().is_some(), "failed to set a layout box");
}
}
}
}
pub(crate) trait NodeExt<'dom> {
/// Returns the image if its loaded, and its size in image pixels
/// adjusted for `image_density`.
fn as_image(&self) -> Option<(Option<Image>, PhysicalSize<f64>)>;
fn as_canvas(&self) -> Option<(CanvasInfo, PhysicalSize<f64>)>;
fn as_iframe(&self) -> Option<(PipelineId, BrowsingContextId)>;
fn as_video(&self) -> Option<(Option<webrender_api::ImageKey>, Option<PhysicalSize<f64>>)>;
fn as_typeless_object_with_data_attribute(&self) -> Option<String>;
fn style(&self, context: &SharedStyleContext) -> ServoArc<ComputedValues>;
fn layout_data_mut(&self) -> AtomicRefMut<'dom, InnerDOMLayoutData>;
fn layout_data(&self) -> Option<AtomicRef<'dom, InnerDOMLayoutData>>;
fn element_box_slot(&self) -> BoxSlot<'dom>;
fn pseudo_element_box_slot(&self, pseudo_element: PseudoElement) -> BoxSlot<'dom>;
/// Remove boxes for the element itself, and all of its pseudo-element boxes.
fn unset_all_boxes(&self);
/// Remove all pseudo-element boxes for this element.
fn unset_all_pseudo_boxes(&self);
fn fragments_for_pseudo(&self, pseudo_element: Option<PseudoElement>) -> Vec<Fragment>;
fn invalidate_cached_fragment(&self);
fn repair_style(&self, context: &SharedStyleContext);
fn take_restyle_damage(&self) -> LayoutDamage;
}
impl<'dom> NodeExt<'dom> for ServoLayoutNode<'dom> {
fn as_image(&self) -> Option<(Option<Image>, PhysicalSize<f64>)> {
let node = self.to_threadsafe();
let (resource, metadata) = node.image_data()?;
let (width, height) = resource
.as_ref()
.map(|image| {
let image_metadata = image.metadata();
(image_metadata.width, image_metadata.height)
})
.or_else(|| metadata.map(|metadata| (metadata.width, metadata.height)))
.unwrap_or((0, 0));
let (mut width, mut height) = (width as f64, height as f64);
if let Some(density) = node.image_density().filter(|density| *density != 1.) {
width /= density;
height /= density;
}
Some((resource, PhysicalSize::new(width, height)))
}
fn as_video(&self) -> Option<(Option<webrender_api::ImageKey>, Option<PhysicalSize<f64>>)> {
let node = self.to_threadsafe();
let data = node.media_data()?;
let natural_size = if let Some(frame) = data.current_frame {
Some(PhysicalSize::new(frame.width.into(), frame.height.into()))
} else {
data.metadata
.map(|meta| PhysicalSize::new(meta.width.into(), meta.height.into()))
};
Some((
data.current_frame.map(|frame| frame.image_key),
natural_size,
))
}
fn as_canvas(&self) -> Option<(CanvasInfo, PhysicalSize<f64>)> {
let node = self.to_threadsafe();
let canvas_data = node.canvas_data()?;
let source = canvas_data.source;
Some((
CanvasInfo { source },
PhysicalSize::new(canvas_data.width.into(), canvas_data.height.into()),
))
}
fn as_iframe(&self) -> Option<(PipelineId, BrowsingContextId)> {
let node = self.to_threadsafe();
match (node.iframe_pipeline_id(), node.iframe_browsing_context_id()) {
(Some(pipeline_id), Some(browsing_context_id)) => {
Some((pipeline_id, browsing_context_id))
},
_ => None,
}
}
fn as_typeless_object_with_data_attribute(&self) -> Option<String> {
if LayoutNode::type_id(self) !=
ScriptLayoutNodeType::Element(LayoutElementType::HTMLObjectElement)
{
return None;
}
// TODO: This is the what the legacy layout system did, but really if Servo
// supports any `<object>` that's an image, it should support those with URLs
// and `type` attributes with image mime types.
let element = self.to_threadsafe().as_element()?;
if element.get_attr(&ns!(), &local_name!("type")).is_some() {
return None;
}
element
.get_attr(&ns!(), &local_name!("data"))
.map(|string| string.to_owned())
}
fn style(&self, context: &SharedStyleContext) -> ServoArc<ComputedValues> {
self.to_threadsafe().style(context)
}
fn layout_data_mut(&self) -> AtomicRefMut<'dom, InnerDOMLayoutData> {
if LayoutNode::layout_data(self).is_none() {
self.initialize_layout_data::<DOMLayoutData>();
}
LayoutNode::layout_data(self)
.unwrap()
.as_any()
.downcast_ref::<DOMLayoutData>()
.unwrap()
.0
.borrow_mut()
}
fn layout_data(&self) -> Option<AtomicRef<'dom, InnerDOMLayoutData>> {
LayoutNode::layout_data(self).map(|data| {
data.as_any()
.downcast_ref::<DOMLayoutData>()
.unwrap()
.0
.borrow()
})
}
fn element_box_slot(&self) -> BoxSlot<'dom> {
self.layout_data_mut().self_box.clone().into()
}
fn pseudo_element_box_slot(&self, pseudo_element: PseudoElement) -> BoxSlot<'dom> {
let mut layout_data = self.layout_data_mut();
let box_slot = ArcRefCell::new(None);
layout_data.pseudo_boxes.push(PseudoLayoutData {
pseudo: pseudo_element,
box_slot: box_slot.clone(),
});
box_slot.into()
}
fn unset_all_boxes(&self) {
let mut layout_data = self.layout_data_mut();
*layout_data.self_box.borrow_mut() = None;
layout_data.pseudo_boxes.clear();
// Stylo already takes care of removing all layout data
// for DOM descendants of elements with `display: none`.
}
fn unset_all_pseudo_boxes(&self) {
self.layout_data_mut().pseudo_boxes.clear();
}
fn invalidate_cached_fragment(&self) {
let data = self.layout_data_mut();
if let Some(data) = data.self_box.borrow_mut().as_ref() {
data.invalidate_cached_fragment();
}
for pseudo_layout_data in data.pseudo_boxes.iter() {
if let Some(layout_box) = pseudo_layout_data.box_slot.borrow().as_ref() {
layout_box.invalidate_cached_fragment();
}
}
}
fn fragments_for_pseudo(&self, pseudo_element: Option<PseudoElement>) -> Vec<Fragment> {
let Some(layout_data) = NodeExt::layout_data(self) else {
return vec![];
};
let Some(layout_data) = layout_data.for_pseudo(pseudo_element) else {
return vec![];
};
layout_data
.as_ref()
.map(LayoutBox::fragments)
.unwrap_or_default()
}
fn repair_style(&self, context: &SharedStyleContext) {
let data = self.layout_data_mut();
if let Some(layout_object) = &*data.self_box.borrow() {
let style = self.to_threadsafe().style(context);
layout_object.repair_style(context, self, &style);
}
for pseudo_layout_data in data.pseudo_boxes.iter() {
if let Some(layout_box) = pseudo_layout_data.box_slot.borrow().as_ref() {
if let Some(node) = self.to_threadsafe().with_pseudo(pseudo_layout_data.pseudo) {
layout_box.repair_style(context, self, &node.style(context));
}
}
}
}
fn take_restyle_damage(&self) -> LayoutDamage {
let damage = self
.style_data()
.map(|style_data| std::mem::take(&mut style_data.element_data.borrow_mut().damage))
.unwrap_or_else(RestyleDamage::reconstruct);
LayoutDamage::from_bits_retain(damage.bits())
}
}