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https://github.com/servo/servo.git
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layout: Rewrite the block formatting context/float inline-size
speculation code.
The old code tried to do the speculation as a single bottom-up pass
after intrinsic inline-size calculation, which was unable to handle
cases like this:
<div>
<div style="float: left">Foo</div>
</div>
<div>
<div style="overflow: hidden">Bar</div>
</div>
No single bottom-up pass could possibly handle this case, because the
inline-size of the float flowing out of the "Foo" block could never make
it down to the "Bar" block, where it is needed for speculation.
On the pages I tried, this regresses layout performance by 1%-2%.
I first noticed this breaking some pages, like the Google SERPs, several
months ago.
This commit is contained in:
Patrick Walton
parent
9b2ae3a62f
commit
b29719e36b
15 changed files with 346 additions and 184 deletions
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@ -26,11 +26,11 @@
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//! similar methods.
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use app_units::Au;
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use block::BlockFlow;
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use block::{BlockFlow, FormattingContextType};
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use context::LayoutContext;
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use display_list_builder::DisplayListBuildState;
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use euclid::{Point2D, Rect, Size2D};
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use floats::Floats;
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use floats::{Floats, SpeculatedFloatPlacement};
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use flow_list::{FlowList, FlowListIterator, MutFlowListIterator};
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use flow_ref::{self, FlowRef, WeakFlowRef};
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use fragment::{Fragment, FragmentBorderBoxIterator, Overflow, SpecificFragmentInfo};
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@ -231,8 +231,8 @@ pub trait Flow: fmt::Debug + Sync + Send + 'static {
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fn place_float_if_applicable<'a>(&mut self, _: &'a LayoutContext<'a>) {}
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/// Assigns block-sizes in-order; or, if this is a float, places the float. The default
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/// implementation simply assigns block-sizes if this flow is impacted by floats. Returns true
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/// if this child was impacted by floats or false otherwise.
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/// implementation simply assigns block-sizes if this flow might have floats in. Returns true
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/// if it was determined that this child might have had floats in or false otherwise.
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///
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/// `parent_thread_id` is the thread ID of the parent. This is used for the layout tinting
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/// debug mode; if the block size of this flow was determined by its parent, we should treat
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@ -241,16 +241,16 @@ pub trait Flow: fmt::Debug + Sync + Send + 'static {
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layout_context: &'a LayoutContext<'a>,
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parent_thread_id: u8)
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-> bool {
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let impacted = base(self).flags.impacted_by_floats();
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if impacted {
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let might_have_floats_in_or_out = base(self).might_have_floats_in() ||
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base(self).might_have_floats_out();
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if might_have_floats_in_or_out {
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mut_base(self).thread_id = parent_thread_id;
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self.assign_block_size(layout_context);
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mut_base(self).restyle_damage.remove(REFLOW_OUT_OF_FLOW | REFLOW);
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}
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impacted
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might_have_floats_in_or_out
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}
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/// Calculate and set overflow for current flow.
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///
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/// CSS Section 11.1
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/// This is the union of rectangles of the flows for which we define the
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@ -508,6 +508,10 @@ pub trait ImmutableFlowUtils {
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/// Dumps the flow tree for debugging into the given PrintTree.
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fn print_with_tree(self, print_tree: &mut PrintTree);
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/// Returns true if floats might flow through this flow, as determined by the float placement
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/// speculation pass.
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fn floats_might_flow_through(self) -> bool;
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}
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pub trait MutableFlowUtils {
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@ -559,7 +563,7 @@ pub trait MutableOwnedFlowUtils {
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absolute_descendants: &mut AbsoluteDescendants);
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}
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#[derive(RustcEncodable, PartialEq, Debug)]
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#[derive(Copy, Clone, RustcEncodable, PartialEq, Debug)]
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pub enum FlowClass {
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Block,
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Inline,
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@ -576,6 +580,17 @@ pub enum FlowClass {
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Flex,
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}
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impl FlowClass {
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fn is_block_like(self) -> bool {
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match self {
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FlowClass::Block | FlowClass::ListItem | FlowClass::Table | FlowClass::TableRowGroup |
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FlowClass::TableRow | FlowClass::TableCaption | FlowClass::TableCell |
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FlowClass::TableWrapper => true,
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_ => false,
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}
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}
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}
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/// A top-down traversal.
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pub trait PreorderFlowTraversal {
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/// The operation to perform. Return true to continue or false to stop.
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@ -615,21 +630,6 @@ pub trait InorderFlowTraversal {
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bitflags! {
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#[doc = "Flags used in flows."]
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flags FlowFlags: u32 {
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// floated descendants flags
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#[doc = "Whether this flow has descendants that float left in the same block formatting"]
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#[doc = "context."]
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const HAS_LEFT_FLOATED_DESCENDANTS = 0b0000_0000_0000_0000_0001,
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#[doc = "Whether this flow has descendants that float right in the same block formatting"]
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#[doc = "context."]
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const HAS_RIGHT_FLOATED_DESCENDANTS = 0b0000_0000_0000_0000_0010,
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#[doc = "Whether this flow is impacted by floats to the left in the same block formatting"]
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#[doc = "context (i.e. its height depends on some prior flows with `float: left`)."]
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const IMPACTED_BY_LEFT_FLOATS = 0b0000_0000_0000_0000_0100,
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#[doc = "Whether this flow is impacted by floats to the right in the same block"]
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#[doc = "formatting context (i.e. its height depends on some prior flows with `float:"]
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#[doc = "right`)."]
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const IMPACTED_BY_RIGHT_FLOATS = 0b0000_0000_0000_0000_1000,
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// text align flags
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#[doc = "Whether this flow must have its own layer. Even if this flag is not set, it might"]
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#[doc = "get its own layer if it's deemed to be likely to overlap flows with their own"]
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@ -704,20 +704,6 @@ impl FlowFlags {
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self.insert(other & HAS_FLOATED_DESCENDANTS_BITMASK);
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}
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#[inline]
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pub fn impacted_by_floats(&self) -> bool {
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self.contains(IMPACTED_BY_LEFT_FLOATS) || self.contains(IMPACTED_BY_RIGHT_FLOATS)
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}
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#[inline]
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pub fn set(&mut self, flags: FlowFlags, value: bool) {
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if value {
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self.insert(flags);
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} else {
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self.remove(flags);
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}
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}
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#[inline]
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pub fn float_kind(&self) -> float::T {
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if self.contains(FLOATS_LEFT) {
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@ -910,6 +896,12 @@ pub struct BaseFlow {
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/// The floats next to this flow.
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pub floats: Floats,
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/// Metrics for floats in computed during the float metrics speculation phase.
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pub speculated_float_placement_in: SpeculatedFloatPlacement,
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/// Metrics for floats out computed during the float metrics speculation phase.
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pub speculated_float_placement_out: SpeculatedFloatPlacement,
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/// The collapsible margins for this flow, if any.
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pub collapsible_margins: CollapsibleMargins,
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@ -994,9 +986,11 @@ impl fmt::Debug for BaseFlow {
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};
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write!(f,
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"sc={:?} pos={:?}, overflow={:?}{}{}{}",
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"sc={:?} pos={:?}, floatspec-in={:?}, floatspec-out={:?}, overflow={:?}{}{}{}",
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self.stacking_context_id,
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self.position,
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self.speculated_float_placement_in,
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self.speculated_float_placement_out,
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self.overflow,
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child_count_string,
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absolute_descendants_string,
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@ -1122,6 +1116,8 @@ impl BaseFlow {
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collapsible_margins: CollapsibleMargins::new(),
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stacking_relative_position: Point2D::zero(),
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abs_descendants: AbsoluteDescendants::new(),
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speculated_float_placement_in: SpeculatedFloatPlacement::zero(),
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speculated_float_placement_out: SpeculatedFloatPlacement::zero(),
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block_container_inline_size: Au(0),
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block_container_writing_mode: writing_mode,
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block_container_explicit_block_size: None,
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@ -1172,17 +1168,24 @@ impl BaseFlow {
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kid.collect_stacking_contexts(parent_id, contexts);
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}
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}
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#[inline]
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pub fn might_have_floats_in(&self) -> bool {
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self.speculated_float_placement_in.left > Au(0) ||
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self.speculated_float_placement_in.right > Au(0)
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}
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#[inline]
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pub fn might_have_floats_out(&self) -> bool {
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self.speculated_float_placement_out.left > Au(0) ||
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self.speculated_float_placement_out.right > Au(0)
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}
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}
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impl<'a> ImmutableFlowUtils for &'a Flow {
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/// Returns true if this flow is a block flow or subclass thereof.
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fn is_block_like(self) -> bool {
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match self.class() {
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FlowClass::Block | FlowClass::ListItem | FlowClass::Table | FlowClass::TableRowGroup |
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FlowClass::TableRow | FlowClass::TableCaption | FlowClass::TableCell |
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FlowClass::TableWrapper => true,
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_ => false,
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}
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self.class().is_block_like()
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}
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/// Returns true if this flow is a proper table child.
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@ -1378,6 +1381,19 @@ impl<'a> ImmutableFlowUtils for &'a Flow {
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}
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print_tree.end_level();
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}
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fn floats_might_flow_through(self) -> bool {
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if !base(self).might_have_floats_in() && !base(self).might_have_floats_out() {
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return false
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}
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if self.is_root() {
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return false
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}
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if !self.is_block_like() {
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return true
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}
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self.as_block().formatting_context_type() == FormattingContextType::None
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}
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}
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impl<'a> MutableFlowUtils for &'a mut Flow {
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@ -1563,3 +1579,4 @@ impl OpaqueFlow {
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}
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}
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}
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