/* 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 http://mozilla.org/MPL/2.0/. */
//! Servo's experimental layout system builds a tree of `Flow` and `Fragment` objects and solves
//! layout constraints to obtain positions and display attributes of tree nodes. Positions are
//! computed in several tree traversals driven by the fundamental data dependencies required by
/// inline and block layout.
///
/// Flows are interior nodes in the layout tree and correspond closely to *flow contexts* in the
/// CSS specification. Flows are responsible for positioning their child flow contexts and
/// fragments. Flows have purpose-specific fields, such as auxiliary line structs, out-of-flow
/// child lists, and so on.
///
/// Currently, the important types of flows are:
///
/// * `BlockFlow`: A flow that establishes a block context. It has several child flows, each of
/// which are positioned according to block formatting context rules (CSS block boxes). Block
/// flows also contain a single box to represent their rendered borders, padding, etc.
/// The BlockFlow at the root of the tree has special behavior: it stretches to the boundaries of
/// the viewport.
///
/// * `InlineFlow`: A flow that establishes an inline context. It has a flat list of child
/// fragments/flows that are subject to inline layout and line breaking and structs to represent
/// line breaks and mapping to CSS boxes, for the purpose of handling `getClientRects()` and
/// similar methods.
use css::node_style::StyledNode;
use block::BlockFlow;
use context::LayoutContext;
use display_list_builder::DisplayListBuildingResult;
use floats::Floats;
use flow_list::{FlowList, FlowListIterator, MutFlowListIterator};
use flow_ref::{FlowRef, WeakFlowRef};
use fragment::{Fragment, FragmentBorderBoxIterator, SpecificFragmentInfo};
use incremental::{self, RECONSTRUCT_FLOW, REFLOW, REFLOW_OUT_OF_FLOW, RestyleDamage};
use inline::InlineFlow;
use model::{CollapsibleMargins, IntrinsicISizes, MarginCollapseInfo};
use parallel::FlowParallelInfo;
use table::{ColumnComputedInlineSize, ColumnIntrinsicInlineSize, TableFlow};
use table_caption::TableCaptionFlow;
use table_cell::TableCellFlow;
use table_colgroup::TableColGroupFlow;
use table_row::TableRowFlow;
use table_rowgroup::TableRowGroupFlow;
use table_wrapper::TableWrapperFlow;
use multicol::MulticolFlow;
use wrapper::ThreadSafeLayoutNode;
use euclid::{Point2D, Rect, Size2D};
use gfx::display_list::ClippingRegion;
use msg::compositor_msg::LayerId;
use msg::constellation_msg::ConstellationChan;
use rustc_serialize::{Encoder, Encodable};
use std::fmt;
use std::iter::Zip;
use std::mem;
use std::raw;
use std::slice::IterMut;
use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};
use style::computed_values::{clear, empty_cells, float, position, text_align};
use style::properties::ComputedValues;
use style::values::computed::LengthOrPercentageOrAuto;
use util::geometry::{Au, ZERO_RECT};
use util::logical_geometry::{LogicalRect, LogicalSize, WritingMode};
/// Virtual methods that make up a float context.
///
/// Note that virtual methods have a cost; we should not overuse them in Servo. Consider adding
/// methods to `ImmutableFlowUtils` or `MutableFlowUtils` before adding more methods here.
pub trait Flow: fmt::Debug + Sync {
// RTTI
//
// TODO(pcwalton): Use Rust's RTTI, once that works.
/// Returns the class of flow that this is.
fn class(&self) -> FlowClass;
/// If this is a block flow, returns the underlying object, borrowed immutably. Fails
/// otherwise.
fn as_immutable_block<'a>(&'a self) -> &'a BlockFlow {
panic!("called as_immutable_block() on a non-block flow")
}
/// If this is a block flow, returns the underlying object. Fails otherwise.
fn as_block<'a>(&'a mut self) -> &'a mut BlockFlow {
debug!("called as_block() on a flow of type {:?}", self.class());
panic!("called as_block() on a non-block flow")
}
/// If this is an inline flow, returns the underlying object, borrowed immutably. Fails
/// otherwise.
fn as_immutable_inline<'a>(&'a self) -> &'a InlineFlow {
panic!("called as_immutable_inline() on a non-inline flow")
}
/// If this is an inline flow, returns the underlying object. Fails otherwise.
fn as_inline<'a>(&'a mut self) -> &'a mut InlineFlow {
panic!("called as_inline() on a non-inline flow")
}
/// If this is a table wrapper flow, returns the underlying object. Fails otherwise.
fn as_table_wrapper<'a>(&'a mut self) -> &'a mut TableWrapperFlow {
panic!("called as_table_wrapper() on a non-tablewrapper flow")
}
/// If this is a table wrapper flow, returns the underlying object, borrowed immutably. Fails
/// otherwise.
fn as_immutable_table_wrapper<'a>(&'a self) -> &'a TableWrapperFlow {
panic!("called as_immutable_table_wrapper() on a non-tablewrapper flow")
}
/// If this is a table flow, returns the underlying object. Fails otherwise.
fn as_table<'a>(&'a mut self) -> &'a mut TableFlow {
panic!("called as_table() on a non-table flow")
}
/// If this is a table flow, returns the underlying object, borrowed immutably. Fails otherwise.
fn as_immutable_table<'a>(&'a self) -> &'a TableFlow {
panic!("called as_table() on a non-table flow")
}
/// If this is a table colgroup flow, returns the underlying object. Fails otherwise.
fn as_table_colgroup<'a>(&'a mut self) -> &'a mut TableColGroupFlow {
panic!("called as_table_colgroup() on a non-tablecolgroup flow")
}
/// If this is a table rowgroup flow, returns the underlying object. Fails otherwise.
fn as_table_rowgroup<'a>(&'a mut self) -> &'a mut TableRowGroupFlow {
panic!("called as_table_rowgroup() on a non-tablerowgroup flow")
}
/// If this is a table rowgroup flow, returns the underlying object, borrowed immutably. Fails
/// otherwise.
fn as_immutable_table_rowgroup<'a>(&'a self) -> &'a TableRowGroupFlow {
panic!("called as_table_rowgroup() on a non-tablerowgroup flow")
}
/// If this is a table row flow, returns the underlying object. Fails otherwise.
fn as_table_row<'a>(&'a mut self) -> &'a mut TableRowFlow {
panic!("called as_table_row() on a non-tablerow flow")
}
/// If this is a table row flow, returns the underlying object, borrowed immutably. Fails
/// otherwise.
fn as_immutable_table_row<'a>(&'a self) -> &'a TableRowFlow {
panic!("called as_table_row() on a non-tablerow flow")
}
/// If this is a table cell flow, returns the underlying object. Fails otherwise.
fn as_table_caption<'a>(&'a mut self) -> &'a mut TableCaptionFlow {
panic!("called as_table_caption() on a non-tablecaption flow")
}
/// If this is a table cell flow, returns the underlying object. Fails otherwise.
fn as_table_cell<'a>(&'a mut self) -> &'a mut TableCellFlow {
panic!("called as_table_cell() on a non-tablecell flow")
}
/// If this is a multicol flow, returns the underlying object. Fails otherwise.
fn as_multicol<'a>(&'a mut self) -> &'a mut MulticolFlow {
panic!("called as_multicol() on a non-multicol flow")
}
/// If this is a table cell flow, returns the underlying object, borrowed immutably. Fails
/// otherwise.
fn as_immutable_table_cell<'a>(&'a self) -> &'a TableCellFlow {
panic!("called as_table_cell() on a non-tablecell flow")
}
/// If this is a table row, table rowgroup, or table flow, returns column intrinsic
/// inline-sizes. Fails otherwise.
fn column_intrinsic_inline_sizes<'a>(&'a mut self) -> &'a mut Vec<ColumnIntrinsicInlineSize> {
panic!("called column_intrinsic_inline_sizes() on non-table flow")
}
/// If this is a table row, table rowgroup, or table flow, returns column computed
/// inline-sizes. Fails otherwise.
fn column_computed_inline_sizes<'a>(&'a mut self) -> &'a mut Vec<ColumnComputedInlineSize> {
panic!("called column_intrinsic_inline_sizes() on non-table flow")
}
// Main methods
/// Pass 1 of reflow: computes minimum and preferred inline-sizes.
///
/// Recursively (bottom-up) determine the flow's minimum and preferred inline-sizes. When
/// called on this flow, all child flows have had their minimum and preferred inline-sizes set.
/// This function must decide minimum/preferred inline-sizes based on its children's inline-
/// sizes and the dimensions of any boxes it is responsible for flowing.
fn bubble_inline_sizes(&mut self) {
panic!("bubble_inline_sizes not yet implemented")
}
/// Pass 2 of reflow: computes inline-size.
fn assign_inline_sizes(&mut self, _ctx: &LayoutContext) {
panic!("assign_inline_sizes not yet implemented")
}
/// Pass 3a of reflow: computes block-size.
fn assign_block_size<'a>(&mut self, _ctx: &'a LayoutContext<'a>) {
panic!("assign_block_size not yet implemented")
}
/// If this is a float, places it. The default implementation does nothing.
fn place_float_if_applicable<'a>(&mut self, _: &'a LayoutContext<'a>) {}
/// Assigns block-sizes in-order; or, if this is a float, places the float. The default
/// implementation simply assigns block-sizes if this flow is impacted by floats. Returns true
/// if this child was impacted by floats or false otherwise.
///
/// `parent_thread_id` is the thread ID of the parent. This is used for the layout tinting
/// debug mode; if the block size of this flow was determined by its parent, we should treat
/// it as laid out by its parent.
fn assign_block_size_for_inorder_child_if_necessary<'a>(&mut self,
layout_context: &'a LayoutContext<'a>,
parent_thread_id: u8)
-> bool {
let impacted = base(self).flags.impacted_by_floats();
if impacted {
mut_base(self).thread_id = parent_thread_id;
self.assign_block_size(layout_context);
self.store_overflow(layout_context);
mut_base(self).restyle_damage.remove(REFLOW_OUT_OF_FLOW | REFLOW);
}
impacted
}
/// Calculate and set overflow for current flow.
///
/// CSS Section 11.1
/// This is the union of rectangles of the flows for which we define the
/// Containing Block.
///
/// FIXME(pcwalton): This should not be a virtual method, but currently is due to a compiler
/// bug ("the trait `Sized` is not implemented for `self`").
///
/// Assumption: This is called in a bottom-up traversal, so kids' overflows have
/// already been set.
/// Assumption: Absolute descendants have had their overflow calculated.
fn store_overflow(&mut self, _: &LayoutContext) {
// Calculate overflow on a per-fragment basis.
let mut overflow = self.compute_overflow();
match self.class() {
FlowClass::Block |
FlowClass::TableCaption |
FlowClass::TableCell if base(self).children.len() != 0 => {
// FIXME(#2795): Get the real container size.
let container_size = Size2D::zero();
for kid in mut_base(self).children.iter_mut() {
if base(kid).flags.contains(IS_ABSOLUTELY_POSITIONED) {
continue
}
let kid_overflow = base(kid).overflow;
let kid_position = base(kid).position.to_physical(base(kid).writing_mode,
container_size);
overflow = overflow.union(&kid_overflow.translate(&kid_position.origin))
}
for kid in mut_base(self).abs_descendants.iter() {
let kid_overflow = base(kid).overflow;
let kid_position = base(kid).position.to_physical(base(kid).writing_mode,
container_size);
overflow = overflow.union(&kid_overflow.translate(&kid_position.origin))
}
}
_ => {}
}
mut_base(self).overflow = overflow;
}
/// Phase 4 of reflow: computes absolute positions.
fn compute_absolute_position(&mut self, _: &LayoutContext) {
// The default implementation is a no-op.
}
/// Phase 5 of reflow: builds display lists.
fn build_display_list(&mut self, layout_context: &LayoutContext);
/// Returns the union of all overflow rects of all of this flow's fragments.
fn compute_overflow(&self) -> Rect<Au>;
/// Iterates through border boxes of all of this flow's fragments.
fn iterate_through_fragment_border_boxes(&self,
iterator: &mut FragmentBorderBoxIterator,
stacking_context_position: &Point2D<Au>);
/// Mutably iterates through fragments in this flow.
fn mutate_fragments(&mut self, mutator: &mut FnMut(&mut Fragment));
fn compute_collapsible_block_start_margin(&mut self,
_layout_context: &mut LayoutContext,
_margin_collapse_info: &mut MarginCollapseInfo) {
// The default implementation is a no-op.
}
/// Marks this flow as the root flow. The default implementation is a no-op.
fn mark_as_root(&mut self) {}
// Note that the following functions are mostly called using static method
// dispatch, so it's ok to have them in this trait. Plus, they have
// different behaviour for different types of Flow, so they can't go into
// the Immutable / Mutable Flow Utils traits without additional casts.
/// Return true if store overflow is delayed for this flow.
///
/// Currently happens only for absolutely positioned flows.
fn is_store_overflow_delayed(&mut self) -> bool {
false
}
fn is_root(&self) -> bool {
false
}
/// The 'position' property of this flow.
fn positioning(&self) -> position::T {
position::T::static_
}
/// Return true if this flow has position 'fixed'.
fn is_fixed(&self) -> bool {
self.positioning() == position::T::fixed
}
fn contains_positioned_fragments(&self) -> bool {
self.contains_relatively_positioned_fragments() ||
base(self).flags.contains(IS_ABSOLUTELY_POSITIONED)
}
fn contains_relatively_positioned_fragments(&self) -> bool {
self.positioning() == position::T::relative
}
/// Returns true if this is an absolute containing block.
fn is_absolute_containing_block(&self) -> bool {
false
}
/// Updates the inline position of a child flow during the assign-height traversal. At present,
/// this is only used for absolutely-positioned inline-blocks.
fn update_late_computed_inline_position_if_necessary(&mut self, inline_position: Au);
/// Updates the block position of a child flow during the assign-height traversal. At present,
/// this is only used for absolutely-positioned inline-blocks.
fn update_late_computed_block_position_if_necessary(&mut self, block_position: Au);
/// Return the size of the containing block generated by this flow for the absolutely-
/// positioned descendant referenced by `for_flow`. For block flows, this is the padding box.
///
/// NB: Do not change this `&self` to `&mut self` under any circumstances! It has security
/// implications because this can be called on parents concurrently from descendants!
fn generated_containing_block_size(&self, _: OpaqueFlow) -> LogicalSize<Au>;
/// Returns a layer ID for the given fragment.
#[allow(unsafe_code)]
fn layer_id(&self, fragment_id: u32) -> LayerId {
let obj = unsafe { mem::transmute::<&&Self, &raw::TraitObject>(&self) };
LayerId(obj.data as usize, fragment_id)
}
/// Attempts to perform incremental fixup of this flow by replacing its fragment's style with
/// the new style. This can only succeed if the flow has exactly one fragment.
fn repair_style(&mut self, new_style: &Arc<ComputedValues>);
/// Remove any compositor layers associated with this flow
fn remove_compositor_layers(&self, _: ConstellationChan) {}
}
// Base access
#[inline(always)]
#[allow(unsafe_code)]
pub fn base<'a, T: ?Sized + Flow>(this: &'a T) -> &'a BaseFlow {
unsafe {
let obj = mem::transmute::<&&'a T, &'a raw::TraitObject>(&this);
mem::transmute::<*mut (), &'a BaseFlow>(obj.data)
}
}
/// Iterates over the children of this immutable flow.
pub fn imm_child_iter<'a>(flow: &'a Flow) -> FlowListIterator<'a> {
base(flow).children.iter()
}
#[inline(always)]
#[allow(unsafe_code)]
pub fn mut_base<'a, T: ?Sized + Flow>(this: &'a mut T) -> &'a mut BaseFlow {
unsafe {
let obj = mem::transmute::<&&'a mut T, &'a raw::TraitObject>(&this);
mem::transmute::<*mut (), &'a mut BaseFlow>(obj.data)
}
}
/// Iterates over the children of this flow.
pub fn child_iter<'a>(flow: &'a mut Flow) -> MutFlowListIterator<'a> {
mut_base(flow).children.iter_mut()
}
pub trait ImmutableFlowUtils {
// Convenience functions
/// Returns true if this flow is a block flow or subclass thereof.
fn is_block_like(self) -> bool;
/// Returns true if this flow is a table flow.
fn is_table(self) -> bool;
/// Returns true if this flow is a table caption flow.
fn is_table_caption(self) -> bool;
/// Returns true if this flow is a proper table child.
fn is_proper_table_child(self) -> bool;
/// Returns true if this flow is a table row flow.
fn is_table_row(self) -> bool;
/// Returns true if this flow is a table cell flow.
fn is_table_cell(self) -> bool;
/// Returns true if this flow is a table colgroup flow.
fn is_table_colgroup(self) -> bool;
/// Returns true if this flow is a table rowgroup flow.
fn is_table_rowgroup(self) -> bool;
/// Returns true if this flow is one of table-related flows.
fn is_table_kind(self) -> bool;
/// Returns true if anonymous flow is needed between this flow and child flow.
fn need_anonymous_flow(self, child: &Flow) -> bool;
/// Generates missing child flow of this flow.
fn generate_missing_child_flow(self, node: &ThreadSafeLayoutNode) -> FlowRef;
/// Returns true if this flow contains fragments that are roots of an absolute flow tree.
fn contains_roots_of_absolute_flow_tree(&self) -> bool;
/// Returns true if this flow has no children.
fn is_leaf(self) -> bool;
/// Returns the number of children that this flow possesses.
fn child_count(self) -> usize;
/// Return true if this flow is a Block Container.
fn is_block_container(self) -> bool;
/// Returns true if this flow is a block flow.
fn is_block_flow(self) -> bool;
/// Returns true if this flow is an inline flow.
fn is_inline_flow(self) -> bool;
/// Dumps the flow tree for debugging.
fn dump(self);
/// Dumps the flow tree for debugging, with a prefix to indicate that we're at the given level.
fn dump_with_level(self, level: u32);
}
pub trait MutableFlowUtils {
// Traversals
/// Traverses the tree in preorder.
fn traverse_preorder<T:PreorderFlowTraversal>(self, traversal: &T);
/// Traverses the tree in postorder.
fn traverse_postorder<T:PostorderFlowTraversal>(self, traversal: &T);
/// Traverse the Absolute flow tree in preorder.
///
/// Traverse all your direct absolute descendants, who will then traverse
/// their direct absolute descendants.
///
/// Return true if the traversal is to continue or false to stop.
fn traverse_preorder_absolute_flows<T>(&mut self, traversal: &mut T)
where T: PreorderFlowTraversal;
/// Traverse the Absolute flow tree in postorder.
///
/// Return true if the traversal is to continue or false to stop.
fn traverse_postorder_absolute_flows<T>(&mut self, traversal: &mut T)
where T: PostorderFlowTraversal;
// Mutators
/// Calls `repair_style` and `bubble_inline_sizes`. You should use this method instead of
/// calling them individually, since there is no reason not to perform both operations.
fn repair_style_and_bubble_inline_sizes(self, style: &Arc<ComputedValues>);
}
pub trait MutableOwnedFlowUtils {
/// Set absolute descendants for this flow.
///
/// Set this flow as the Containing Block for all the absolute descendants.
fn set_absolute_descendants(&mut self, abs_descendants: AbsDescendants);
}
#[derive(RustcEncodable, PartialEq, Debug)]
pub enum FlowClass {
Block,
Inline,
ListItem,
TableWrapper,
Table,
TableColGroup,
TableRowGroup,
TableRow,
TableCaption,
TableCell,
Multicol,
}
/// A top-down traversal.
pub trait PreorderFlowTraversal {
/// The operation to perform. Return true to continue or false to stop.
fn process(&self, flow: &mut Flow);
/// Returns true if this node must be processed in-order. If this returns false,
/// we skip the operation for this node, but continue processing the descendants.
/// This is called *after* parent nodes are visited.
fn should_process(&self, _flow: &mut Flow) -> bool {
true
}
}
/// A bottom-up traversal, with a optional in-order pass.
pub trait PostorderFlowTraversal {
/// The operation to perform. Return true to continue or false to stop.
fn process(&self, flow: &mut Flow);
/// Returns false if this node must be processed in-order. If this returns false, we skip the
/// operation for this node, but continue processing the ancestors. This is called *after*
/// child nodes are visited.
fn should_process(&self, _flow: &mut Flow) -> bool {
true
}
}
/// An in-order (sequential only) traversal.
pub trait InorderFlowTraversal {
/// The operation to perform. Returns the level of the tree we're at.
fn process(&mut self, flow: &mut Flow, level: u32);
/// Returns true if this node should be processed and false if neither this node nor its
/// descendants should be processed.
fn should_process(&mut self, flow: &mut Flow) -> bool;
}
bitflags! {
#[doc = "Flags used in flows."]
flags FlowFlags: u32 {
// floated descendants flags
#[doc = "Whether this flow has descendants that float left in the same block formatting"]
#[doc = "context."]
const HAS_LEFT_FLOATED_DESCENDANTS = 0b0000_0000_0000_0000_0001,
#[doc = "Whether this flow has descendants that float right in the same block formatting"]
#[doc = "context."]
const HAS_RIGHT_FLOATED_DESCENDANTS = 0b0000_0000_0000_0000_0010,
#[doc = "Whether this flow is impacted by floats to the left in the same block formatting"]
#[doc = "context (i.e. its height depends on some prior flows with `float: left`)."]
const IMPACTED_BY_LEFT_FLOATS = 0b0000_0000_0000_0000_0100,
#[doc = "Whether this flow is impacted by floats to the right in the same block"]
#[doc = "formatting context (i.e. its height depends on some prior flows with `float:"]
#[doc = "right`)."]
const IMPACTED_BY_RIGHT_FLOATS = 0b0000_0000_0000_0000_1000,
// text align flags
#[doc = "Whether this flow contains a flow that has its own layer within the same absolute"]
#[doc = "containing block."]
const LAYERS_NEEDED_FOR_DESCENDANTS = 0b0000_0000_0000_0001_0000,
#[doc = "Whether this flow must have its own layer. Even if this flag is not set, it might"]
#[doc = "get its own layer if it's deemed to be likely to overlap flows with their own"]
#[doc = "layer."]
const NEEDS_LAYER = 0b0000_0000_0000_0010_0000,
#[doc = "Whether this flow is absolutely positioned. This is checked all over layout, so a"]
#[doc = "virtual call is too expensive."]
const IS_ABSOLUTELY_POSITIONED = 0b0000_0000_0000_0100_0000,
#[doc = "Whether this flow clears to the left. This is checked all over layout, so a"]
#[doc = "virtual call is too expensive."]
const CLEARS_LEFT = 0b0000_0000_0000_1000_0000,
#[doc = "Whether this flow clears to the right. This is checked all over layout, so a"]
#[doc = "virtual call is too expensive."]
const CLEARS_RIGHT = 0b0000_0000_0001_0000_0000,
#[doc = "Whether this flow is left-floated. This is checked all over layout, so a"]
#[doc = "virtual call is too expensive."]
const FLOATS_LEFT = 0b0000_0000_0010_0000_0000,
#[doc = "Whether this flow is right-floated. This is checked all over layout, so a"]
#[doc = "virtual call is too expensive."]
const FLOATS_RIGHT = 0b0000_0000_0100_0000_0000,
#[doc = "Text alignment. \
NB: If you update this, update `TEXT_ALIGN_SHIFT` below."]
const TEXT_ALIGN = 0b0000_0111_1000_0000_0000,
#[doc = "Whether this flow has a fragment with `counter-reset` or `counter-increment` \
styles."]
const AFFECTS_COUNTERS = 0b0000_1000_0000_0000_0000,
#[doc = "Whether this flow's descendants have fragments that affect `counter-reset` or \
`counter-increment` styles."]
const HAS_COUNTER_AFFECTING_CHILDREN = 0b0001_0000_0000_0000_0000,
#[doc = "Whether this flow behaves as though it had `position: static` for the purposes \
of positioning in the inline direction. This is set for flows with `position: \
static` and `position: relative` as well as absolutely-positioned flows with \
unconstrained positions in the inline direction."]
const INLINE_POSITION_IS_STATIC = 0b0010_0000_0000_0000_0000,
#[doc = "Whether this flow behaves as though it had `position: static` for the purposes \
of positioning in the block direction. This is set for flows with `position: \
static` and `position: relative` as well as absolutely-positioned flows with \
unconstrained positions in the block direction."]
const BLOCK_POSITION_IS_STATIC = 0b0100_0000_0000_0000_0000,
}
}
// NB: If you update this field, you must update the the floated descendants flags.
/// The bitmask of flags that represent the `has_left_floated_descendants` and
/// `has_right_floated_descendants` fields.
static HAS_FLOATED_DESCENDANTS_BITMASK: FlowFlags = FlowFlags { bits: 0b0000_0011 };
/// The number of bits we must shift off to handle the text alignment field.
///
/// NB: If you update this, update `TEXT_ALIGN` above.
static TEXT_ALIGN_SHIFT: usize = 11;
impl FlowFlags {
/// Propagates text alignment flags from an appropriate parent flow per CSS 2.1.
///
/// FIXME(#2265, pcwalton): It would be cleaner and faster to make this a derived CSS property
/// `-servo-text-align-in-effect`.
pub fn propagate_text_alignment_from_parent(&mut self, parent_flags: FlowFlags) {
self.set_text_align_override(parent_flags);
}
#[inline]
pub fn text_align(self) -> text_align::T {
text_align::T::from_u32((self & TEXT_ALIGN).bits() >> TEXT_ALIGN_SHIFT).unwrap()
}
#[inline]
pub fn set_text_align(&mut self, value: text_align::T) {
*self = (*self & !TEXT_ALIGN) |
FlowFlags::from_bits(value.to_u32() << TEXT_ALIGN_SHIFT).unwrap();
}
#[inline]
pub fn set_text_align_override(&mut self, parent: FlowFlags) {
self.insert(parent & TEXT_ALIGN);
}
#[inline]
pub fn union_floated_descendants_flags(&mut self, other: FlowFlags) {
self.insert(other & HAS_FLOATED_DESCENDANTS_BITMASK);
}
#[inline]
pub fn impacted_by_floats(&self) -> bool {
self.contains(IMPACTED_BY_LEFT_FLOATS) || self.contains(IMPACTED_BY_RIGHT_FLOATS)
}
#[inline]
pub fn set(&mut self, flags: FlowFlags, value: bool) {
if value {
self.insert(flags);
} else {
self.remove(flags);
}
}
#[inline]
pub fn float_kind(&self) -> float::T {
if self.contains(FLOATS_LEFT) {
float::T::left
} else if self.contains(FLOATS_RIGHT) {
float::T::right
} else {
float::T::none
}
}
#[inline]
pub fn is_float(&self) -> bool {
self.contains(FLOATS_LEFT) || self.contains(FLOATS_RIGHT)
}
#[inline]
pub fn clears_floats(&self) -> bool {
self.contains(CLEARS_LEFT) || self.contains(CLEARS_RIGHT)
}
}
/// The Descendants of a flow.
///
/// Also, details about their position wrt this flow.
#[derive(Clone)]
pub struct Descendants {
/// Links to every descendant. This must be private because it is unsafe to leak `FlowRef`s to
/// layout.
descendant_links: Vec<FlowRef>,
}
impl Descendants {
pub fn new() -> Descendants {
Descendants {
descendant_links: Vec::new(),
}
}
pub fn len(&self) -> usize {
self.descendant_links.len()
}
pub fn is_empty(&self) -> bool {
self.descendant_links.is_empty()
}
pub fn push(&mut self, given_descendant: FlowRef) {
self.descendant_links.push(given_descendant);
}
/// Push the given descendants on to the existing descendants.
///
/// Ignore any static y offsets, because they are None before layout.
pub fn push_descendants(&mut self, given_descendants: Descendants) {
for elem in given_descendants.descendant_links.into_iter() {
self.descendant_links.push(elem);
}
}
/// Return an iterator over the descendant flows.
pub fn iter<'a>(&'a mut self) -> DescendantIter<'a> {
DescendantIter {
iter: self.descendant_links.iter_mut(),
}
}
}
pub type AbsDescendants = Descendants;
pub struct DescendantIter<'a> {
iter: IterMut<'a, FlowRef>,
}
impl<'a> Iterator for DescendantIter<'a> {
type Item = &'a mut (Flow + 'a);
fn next(&mut self) -> Option<&'a mut (Flow + 'a)> {
self.iter.next().map(|flow| &mut **flow)
}
}
pub type DescendantOffsetIter<'a> = Zip<DescendantIter<'a>, IterMut<'a, Au>>;
/// Information needed to compute absolute (i.e. viewport-relative) flow positions (not to be
/// confused with absolutely-positioned flows).
#[derive(RustcEncodable, Copy, Clone)]
pub struct AbsolutePositionInfo {
/// The size of the containing block for relatively-positioned descendants.
pub relative_containing_block_size: LogicalSize<Au>,
/// The writing mode for `relative_containing_block_size`.
pub relative_containing_block_mode: WritingMode,
/// The position of the absolute containing block relative to the nearest ancestor stacking
/// context. If the absolute containing block establishes the stacking context for this flow,
/// and this flow is not itself absolutely-positioned, then this is (0, 0).
pub stacking_relative_position_of_absolute_containing_block: Point2D<Au>,
/// Whether the absolute containing block forces positioned descendants to be layerized.
///
/// FIXME(pcwalton): Move into `FlowFlags`.
pub layers_needed_for_positioned_flows: bool,
}
impl AbsolutePositionInfo {
pub fn new(writing_mode: WritingMode) -> AbsolutePositionInfo {
// FIXME(pcwalton): The initial relative containing block-size should be equal to the size
// of the root layer.
AbsolutePositionInfo {
relative_containing_block_size: LogicalSize::zero(writing_mode),
relative_containing_block_mode: writing_mode,
stacking_relative_position_of_absolute_containing_block: Point2D::zero(),
layers_needed_for_positioned_flows: false,
}
}
}
/// Data common to all flows.
pub struct BaseFlow {
/// NB: Must be the first element.
///
/// The necessity of this will disappear once we have dynamically-sized types.
strong_ref_count: AtomicUsize,
weak_ref_count: AtomicUsize,
pub restyle_damage: RestyleDamage,
/// The children of this flow.
pub children: FlowList,
/// Intrinsic inline sizes for this flow.
pub intrinsic_inline_sizes: IntrinsicISizes,
/// The upper left corner of the box representing this flow, relative to the box representing
/// its parent flow.
///
/// For absolute flows, this represents the position with respect to its *containing block*.
///
/// This does not include margins in the block flow direction, because those can collapse. So
/// for the block direction (usually vertical), this represents the *border box*. For the
/// inline direction (usually horizontal), this represents the *margin box*.
pub position: LogicalRect<Au>,
/// The amount of overflow of this flow, relative to the containing block. Must include all the
/// pixels of all the display list items for correct invalidation.
pub overflow: Rect<Au>,
/// Data used during parallel traversals.
///
/// TODO(pcwalton): Group with other transient data to save space.
pub parallel: FlowParallelInfo,
/// The floats next to this flow.
pub floats: Floats,
/// The collapsible margins for this flow, if any.
pub collapsible_margins: CollapsibleMargins,
/// The position of this flow relative to the start of the nearest ancestor stacking context.
/// This is computed during the top-down pass of display list construction.
pub stacking_relative_position: Point2D<Au>,
/// Details about descendants with position 'absolute' or 'fixed' for which we are the
/// containing block. This is in tree order. This includes any direct children.
pub abs_descendants: AbsDescendants,
/// The inline-size of the block container of this flow. Used for computing percentage and
/// automatic values for `width`.
pub block_container_inline_size: Au,
/// The writing mode of the block container of this flow.
///
/// FIXME (mbrubeck): Combine this and block_container_inline_size and maybe
/// block_container_explicit_block_size into a struct, to guarantee they are set at the same
/// time? Or just store a link to the containing block flow.
pub block_container_writing_mode: WritingMode,
/// The block-size of the block container of this flow, if it is an explicit size (does not
/// depend on content heights). Used for computing percentage values for `height`.
pub block_container_explicit_block_size: Option<Au>,
/// Reference to the Containing Block, if this flow is absolutely positioned.
pub absolute_cb: ContainingBlockLink,
/// Information needed to compute absolute (i.e. viewport-relative) flow positions (not to be
/// confused with absolutely-positioned flows).
pub absolute_position_info: AbsolutePositionInfo,
/// The clipping region for this flow and its descendants, in layer coordinates.
pub clip: ClippingRegion,
/// The stacking-relative position of the display port.
///
/// FIXME(pcwalton): This might be faster as an Arc, since this varies only
/// per-stacking-context.
pub stacking_relative_position_of_display_port: Rect<Au>,
/// The results of display list building for this flow.
pub display_list_building_result: DisplayListBuildingResult,
/// The writing mode for this flow.
pub writing_mode: WritingMode,
/// For debugging and profiling, the identifier of the thread that laid out this fragment.
pub thread_id: u8,
/// Various flags for flows, tightly packed to save space.
pub flags: FlowFlags,
}
#[allow(unsafe_code)]
unsafe impl Send for BaseFlow {}
#[allow(unsafe_code)]
unsafe impl Sync for BaseFlow {}
impl fmt::Debug for BaseFlow {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f,
"@ {:?}, CC {}, ADC {}",
self.position,
self.parallel.children_count.load(Ordering::SeqCst),
self.abs_descendants.len())
}
}
impl Encodable for BaseFlow {
fn encode<S: Encoder>(&self, e: &mut S) -> Result<(), S::Error> {
e.emit_struct("base", 0, |e| {
try!(e.emit_struct_field("id", 0, |e| self.debug_id().encode(e)));
try!(e.emit_struct_field("stacking_relative_position",
1,
|e| self.stacking_relative_position.encode(e)));
try!(e.emit_struct_field("intrinsic_inline_sizes",
2,
|e| self.intrinsic_inline_sizes.encode(e)));
try!(e.emit_struct_field("position", 3, |e| self.position.encode(e)));
e.emit_struct_field("children", 4, |e| {
e.emit_seq(self.children.len(), |e| {
for (i, c) in self.children.iter().enumerate() {
try!(e.emit_seq_elt(i, |e| {
try!(e.emit_struct("flow", 0, |e| {
try!(e.emit_struct_field("class", 0, |e| c.class().encode(e)));
e.emit_struct_field("data", 1, |e| {
match c.class() {
FlowClass::Block => c.as_immutable_block().encode(e),
FlowClass::Inline => c.as_immutable_inline().encode(e),
FlowClass::Table => c.as_immutable_table().encode(e),
FlowClass::TableWrapper => {
c.as_immutable_table_wrapper().encode(e)
}
FlowClass::TableRowGroup => {
c.as_immutable_table_rowgroup().encode(e)
}
FlowClass::TableRow => {
c.as_immutable_table_row().encode(e)
}
FlowClass::TableCell => {
c.as_immutable_table_cell().encode(e)
}
_ => { Ok(()) } // TODO: Support captions
}
})
}));
Ok(())
}));
}
Ok(())
})
})
})
}
}
impl Drop for BaseFlow {
fn drop(&mut self) {
if self.strong_ref_count.load(Ordering::SeqCst) != 0 &&
self.weak_ref_count.load(Ordering::SeqCst) != 0 {
panic!("Flow destroyed before its ref count hit zero—this is unsafe!")
}
}
}
/// Whether a base flow should be forced to be nonfloated. This can affect e.g. `TableFlow`, which
/// is never floated because the table wrapper flow is the floated one.
#[derive(Clone, PartialEq)]
pub enum ForceNonfloatedFlag {
/// The flow should be floated if the node has a `float` property.
FloatIfNecessary,
/// The flow should be forced to be nonfloated.
ForceNonfloated,
}
impl BaseFlow {
#[inline]
pub fn new(node: Option<ThreadSafeLayoutNode>,
writing_mode: WritingMode,
force_nonfloated: ForceNonfloatedFlag)
-> BaseFlow {
let mut flags = FlowFlags::empty();
match node {
Some(node) => {
let node_style = node.style();
match node_style.get_box().position {
position::T::absolute | position::T::fixed => {
flags.insert(IS_ABSOLUTELY_POSITIONED);
let logical_position = node_style.logical_position();
if logical_position.inline_start == LengthOrPercentageOrAuto::Auto &&
logical_position.inline_end == LengthOrPercentageOrAuto::Auto {
flags.insert(INLINE_POSITION_IS_STATIC);
}
if logical_position.block_start == LengthOrPercentageOrAuto::Auto &&
logical_position.block_end == LengthOrPercentageOrAuto::Auto {
flags.insert(BLOCK_POSITION_IS_STATIC);
}
}
_ => flags.insert(BLOCK_POSITION_IS_STATIC | INLINE_POSITION_IS_STATIC),
}
if force_nonfloated == ForceNonfloatedFlag::FloatIfNecessary {
match node_style.get_box().float {
float::T::none => {}
float::T::left => flags.insert(FLOATS_LEFT),
float::T::right => flags.insert(FLOATS_RIGHT),
}
}
match node_style.get_box().clear {
clear::T::none => {}
clear::T::left => flags.insert(CLEARS_LEFT),
clear::T::right => flags.insert(CLEARS_RIGHT),
clear::T::both => {
flags.insert(CLEARS_LEFT);
flags.insert(CLEARS_RIGHT);
}
}
if !node_style.get_counters().counter_reset.0.is_empty() ||
!node_style.get_counters().counter_increment.0.is_empty() {
flags.insert(AFFECTS_COUNTERS)
}
}
None => flags.insert(BLOCK_POSITION_IS_STATIC | INLINE_POSITION_IS_STATIC),
}
// New flows start out as fully damaged.
let mut damage = incremental::rebuild_and_reflow();
damage.remove(RECONSTRUCT_FLOW);
BaseFlow {
strong_ref_count: AtomicUsize::new(1),
weak_ref_count: AtomicUsize::new(1),
restyle_damage: damage,
children: FlowList::new(),
intrinsic_inline_sizes: IntrinsicISizes::new(),
position: LogicalRect::zero(writing_mode),
overflow: ZERO_RECT,
parallel: FlowParallelInfo::new(),
floats: Floats::new(writing_mode),
collapsible_margins: CollapsibleMargins::new(),
stacking_relative_position: Point2D::zero(),
abs_descendants: Descendants::new(),
block_container_inline_size: Au(0),
block_container_writing_mode: writing_mode,
block_container_explicit_block_size: None,
absolute_cb: ContainingBlockLink::new(),
display_list_building_result: DisplayListBuildingResult::None,
absolute_position_info: AbsolutePositionInfo::new(writing_mode),
clip: ClippingRegion::max(),
stacking_relative_position_of_display_port: Rect::zero(),
flags: flags,
writing_mode: writing_mode,
thread_id: 0,
}
}
pub fn child_iter<'a>(&'a mut self) -> MutFlowListIterator<'a> {
self.children.iter_mut()
}
#[allow(unsafe_code)]
pub unsafe fn strong_ref_count<'a>(&'a self) -> &'a AtomicUsize {
&self.strong_ref_count
}
#[allow(unsafe_code)]
pub unsafe fn weak_ref_count<'a>(&'a self) -> &'a AtomicUsize {
&self.weak_ref_count
}
pub fn debug_id(&self) -> usize {
let p = self as *const _;
p as usize
}
/// Ensures that all display list items generated by this flow are within the flow's overflow
/// rect. This should only be used for debugging.
pub fn validate_display_list_geometry(&self) {
// FIXME(pcwalton, #2795): Get the real container size.
let container_size = Size2D::zero();
let position_with_overflow = self.position
.to_physical(self.writing_mode, container_size)
.union(&self.overflow);
let bounds = Rect::new(self.stacking_relative_position, position_with_overflow.size);
let all_items = match self.display_list_building_result {
DisplayListBuildingResult::None => Vec::new(),
DisplayListBuildingResult::StackingContext(ref stacking_context) => {
stacking_context.display_list.all_display_items()
}
DisplayListBuildingResult::Normal(ref display_list) => display_list.all_display_items(),
};
for item in all_items.iter() {
let paint_bounds = item.base().clip.clone().intersect_rect(&item.base().bounds);
if !paint_bounds.might_be_nonempty() {
continue;
}
if bounds.union(&paint_bounds.bounding_rect()) != bounds {
error!("DisplayList item {:?} outside of Flow overflow ({:?})", item, paint_bounds);
}
}
}
}
impl<'a> ImmutableFlowUtils for &'a (Flow + 'a) {
/// Returns true if this flow is a block flow or subclass thereof.
fn is_block_like(self) -> bool {
match self.class() {
FlowClass::Block | FlowClass::ListItem | FlowClass::Table | FlowClass::TableRowGroup |
FlowClass::TableRow | FlowClass::TableCaption | FlowClass::TableCell |
FlowClass::TableWrapper => true,
_ => false,
}
}
/// Returns true if this flow is a proper table child.
/// 'Proper table child' is defined as table-row flow, table-rowgroup flow,
/// table-column-group flow, or table-caption flow.
fn is_proper_table_child(self) -> bool {
match self.class() {
FlowClass::TableRow | FlowClass::TableRowGroup |
FlowClass::TableColGroup | FlowClass::TableCaption => true,
_ => false,
}
}
/// Returns true if this flow is a table row flow.
fn is_table_row(self) -> bool {
match self.class() {
FlowClass::TableRow => true,
_ => false,
}
}
/// Returns true if this flow is a table cell flow.
fn is_table_cell(self) -> bool {
match self.class() {
FlowClass::TableCell => true,
_ => false,
}
}
/// Returns true if this flow is a table colgroup flow.
fn is_table_colgroup(self) -> bool {
match self.class() {
FlowClass::TableColGroup => true,
_ => false,
}
}
/// Returns true if this flow is a table flow.
fn is_table(self) -> bool {
match self.class() {
FlowClass::Table => true,
_ => false,
}
}
/// Returns true if this flow is a table caption flow.
fn is_table_caption(self) -> bool {
match self.class() {
FlowClass::TableCaption => true,
_ => false,
}
}
/// Returns true if this flow is a table rowgroup flow.
fn is_table_rowgroup(self) -> bool {
match self.class() {
FlowClass::TableRowGroup => true,
_ => false,
}
}
/// Returns true if this flow is one of table-related flows.
fn is_table_kind(self) -> bool {
match self.class() {
FlowClass::TableWrapper | FlowClass::Table |
FlowClass::TableColGroup | FlowClass::TableRowGroup |
FlowClass::TableRow | FlowClass::TableCaption | FlowClass::TableCell => true,
_ => false,
}
}
/// Returns true if anonymous flow is needed between this flow and child flow.
/// Spec: http://www.w3.org/TR/CSS21/tables.html#anonymous-boxes
fn need_anonymous_flow(self, child: &Flow) -> bool {
match self.class() {
FlowClass::Table => !child.is_proper_table_child(),
FlowClass::TableRowGroup => !child.is_table_row(),
FlowClass::TableRow => !child.is_table_cell(),
_ => false
}
}
/// Generates missing child flow of this flow.
fn generate_missing_child_flow(self, node: &ThreadSafeLayoutNode) -> FlowRef {
let flow = match self.class() {
FlowClass::Table | FlowClass::TableRowGroup => {
let fragment =
Fragment::new_anonymous_from_specific_info(node,
SpecificFragmentInfo::TableRow);
box TableRowFlow::from_node_and_fragment(node, fragment) as Box<Flow>
},
FlowClass::TableRow => {
let fragment =
Fragment::new_anonymous_from_specific_info(node,
SpecificFragmentInfo::TableCell);
let hide = node.style().get_inheritedtable().empty_cells == empty_cells::T::hide;
box TableCellFlow::from_node_fragment_and_visibility_flag(node, fragment, !hide) as
Box<Flow>
},
_ => {
panic!("no need to generate a missing child")
}
};
FlowRef::new(flow)
}
/// Returns true if this flow contains fragments that are roots of an absolute flow tree.
fn contains_roots_of_absolute_flow_tree(&self) -> bool {
self.contains_relatively_positioned_fragments() || self.is_root()
}
/// Returns true if this flow has no children.
fn is_leaf(self) -> bool {
base(self).children.len() == 0
}
/// Returns the number of children that this flow possesses.
fn child_count(self) -> usize {
base(self).children.len()
}
/// Return true if this flow is a Block Container.
///
/// Except for table fragments and replaced elements, block-level fragments (`BlockFlow`) are
/// also block container fragments.
/// Non-replaced inline blocks and non-replaced table cells are also block
/// containers.
fn is_block_container(self) -> bool {
match self.class() {
// TODO: Change this when inline-blocks are supported.
FlowClass::Block | FlowClass::TableCaption | FlowClass::TableCell => {
// FIXME: Actually check the type of the node
self.child_count() != 0
}
_ => false,
}
}
/// Returns true if this flow is a block flow.
fn is_block_flow(self) -> bool {
match self.class() {
FlowClass::Block => true,
_ => false,
}
}
/// Returns true if this flow is an inline flow.
fn is_inline_flow(self) -> bool {
match self.class() {
FlowClass::Inline => true,
_ => false,
}
}
/// Dumps the flow tree for debugging.
fn dump(self) {
self.dump_with_level(0)
}
/// Dumps the flow tree for debugging, with a prefix to indicate that we're at the given level.
fn dump_with_level(self, level: u32) {
let mut indent = String::new();
for _ in 0..level {
indent.push_str("| ")
}
println!("{}+ {:?}", indent, self);
for kid in imm_child_iter(self) {
kid.dump_with_level(level + 1)
}
}
}
impl<'a> MutableFlowUtils for &'a mut (Flow + 'a) {
/// Traverses the tree in preorder.
fn traverse_preorder<T:PreorderFlowTraversal>(self, traversal: &T) {
if traversal.should_process(self) {
traversal.process(self);
}
for kid in child_iter(self) {
kid.traverse_preorder(traversal);
}
}
/// Traverses the tree in postorder.
fn traverse_postorder<T:PostorderFlowTraversal>(self, traversal: &T) {
for kid in child_iter(self) {
kid.traverse_postorder(traversal);
}
if traversal.should_process(self) {
traversal.process(self)
}
}
/// Calls `repair_style` and `bubble_inline_sizes`. You should use this method instead of
/// calling them individually, since there is no reason not to perform both operations.
fn repair_style_and_bubble_inline_sizes(self, style: &Arc<ComputedValues>) {
self.repair_style(style);
self.bubble_inline_sizes();
}
/// Traverse the Absolute flow tree in preorder.
///
/// Traverse all your direct absolute descendants, who will then traverse
/// their direct absolute descendants.
///
/// Return true if the traversal is to continue or false to stop.
fn traverse_preorder_absolute_flows<T>(&mut self, traversal: &mut T)
where T: PreorderFlowTraversal {
traversal.process(*self);
let descendant_offset_iter = mut_base(*self).abs_descendants.iter();
for ref mut descendant_link in descendant_offset_iter {
descendant_link.traverse_preorder_absolute_flows(traversal)
}
}
/// Traverse the Absolute flow tree in postorder.
///
/// Return true if the traversal is to continue or false to stop.
fn traverse_postorder_absolute_flows<T>(&mut self, traversal: &mut T)
where T: PostorderFlowTraversal {
for mut descendant_link in mut_base(*self).abs_descendants.iter() {
descendant_link.traverse_postorder_absolute_flows(traversal);
}
traversal.process(*self)
}
}
impl MutableOwnedFlowUtils for FlowRef {
/// Set absolute descendants for this flow.
///
/// Set yourself as the Containing Block for all the absolute descendants.
///
/// This is called during flow construction, so nothing else can be accessing the descendant
/// flows. This is enforced by the fact that we have a mutable `FlowRef`, which only flow
/// construction is allowed to possess.
fn set_absolute_descendants(&mut self, abs_descendants: AbsDescendants) {
let this = self.clone();
let base = mut_base(&mut **self);
base.abs_descendants = abs_descendants;
for descendant_link in base.abs_descendants.iter() {
let descendant_base = mut_base(descendant_link);
descendant_base.absolute_cb.set(this.clone());
}
}
}
/// A link to a flow's containing block.
///
/// This cannot safely be a `Flow` pointer because this is a pointer *up* the tree, not *down* the
/// tree. A pointer up the tree is unsafe during layout because it can be used to access a node
/// with an immutable reference while that same node is being laid out, causing possible iterator
/// invalidation and use-after-free.
///
/// FIXME(pcwalton): I think this would be better with a borrow flag instead of `unsafe`.
pub struct ContainingBlockLink {
/// The pointer up to the containing block.
link: Option<WeakFlowRef>,
}
impl ContainingBlockLink {
fn new() -> ContainingBlockLink {
ContainingBlockLink {
link: None,
}
}
fn set(&mut self, link: FlowRef) {
self.link = Some(link.downgrade())
}
#[allow(unsafe_code)]
pub unsafe fn get<'a>(&'a mut self) -> &'a mut Option<WeakFlowRef> {
&mut self.link
}
#[inline]
pub fn generated_containing_block_size(&mut self, for_flow: OpaqueFlow) -> LogicalSize<Au> {
match self.link {
None => {
panic!("Link to containing block not established; perhaps you forgot to call \
`set_absolute_descendants`?")
}
Some(ref mut link) => link.generated_containing_block_size(for_flow),
}
}
}
/// A wrapper for the pointer address of a flow. These pointer addresses may only be compared for
/// equality with other such pointer addresses, never dereferenced.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct OpaqueFlow(pub usize);
impl OpaqueFlow {
#[allow(unsafe_code)]
pub fn from_flow(flow: &Flow) -> OpaqueFlow {
unsafe {
let object = mem::transmute::<&Flow,raw::TraitObject>(flow);
OpaqueFlow(object.data as usize)
}
}
pub fn from_base_flow(base_flow: &BaseFlow) -> OpaqueFlow {
OpaqueFlow(base_flow as *const BaseFlow as usize)
}
}