зеркало из https://github.com/mozilla/gecko-dev.git
113 строки
3.8 KiB
Rust
113 строки
3.8 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#![crate_name = "gfx_traits"]
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#![crate_type = "rlib"]
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#![deny(unsafe_code)]
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extern crate malloc_size_of;
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#[macro_use] extern crate malloc_size_of_derive;
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#[macro_use] extern crate range;
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#[macro_use] extern crate serde;
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pub mod print_tree;
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use range::RangeIndex;
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use std::sync::atomic::{ATOMIC_USIZE_INIT, AtomicUsize, Ordering};
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/// A newtype struct for denoting the age of messages; prevents race conditions.
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#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize)]
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pub struct Epoch(pub u32);
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impl Epoch {
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pub fn next(&mut self) {
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self.0 += 1;
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}
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}
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/// A unique ID for every stacking context.
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#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize)]
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pub struct StackingContextId(
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/// The identifier for this StackingContext, derived from the Flow's memory address
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/// and fragment type. As a space optimization, these are combined into a single word.
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pub u64
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);
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impl StackingContextId {
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/// Returns the stacking context ID for the outer document/layout root.
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#[inline]
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pub fn root() -> StackingContextId {
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StackingContextId(0)
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}
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pub fn next(&self) -> StackingContextId {
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let StackingContextId(id) = *self;
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StackingContextId(id + 1)
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}
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}
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int_range_index! {
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#[derive(Deserialize, Serialize)]
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#[doc = "An index that refers to a byte offset in a text run. This could \
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point to the middle of a glyph."]
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#[derive(MallocSizeOf)]
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struct ByteIndex(isize)
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}
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/// The type of fragment that a stacking context represents.
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///
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/// This can only ever grow to maximum 4 entries. That's because we cram the value of this enum
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/// into the lower 2 bits of the `StackingContextId`, which otherwise contains a 32-bit-aligned
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/// heap address.
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#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize)]
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pub enum FragmentType {
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/// A StackingContext for the fragment body itself.
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FragmentBody,
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/// A StackingContext created to contain ::before pseudo-element content.
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BeforePseudoContent,
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/// A StackingContext created to contain ::after pseudo-element content.
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AfterPseudoContent,
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}
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/// The next ID that will be used for a special stacking context.
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///
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/// A special stacking context is a stacking context that is one of (a) the outer stacking context
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/// of an element with `overflow: scroll`; (b) generated content; (c) both (a) and (b).
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static NEXT_SPECIAL_STACKING_CONTEXT_ID: AtomicUsize = ATOMIC_USIZE_INIT;
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/// If none of the bits outside this mask are set, the stacking context is a special stacking
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/// context.
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///
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/// Note that we assume that the top 16 bits of the address space are unused on the platform.
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const SPECIAL_STACKING_CONTEXT_ID_MASK: usize = 0xffff;
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/// Returns a new stacking context ID for a special stacking context.
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fn next_special_id() -> usize {
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// We shift this left by 2 to make room for the fragment type ID.
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((NEXT_SPECIAL_STACKING_CONTEXT_ID.fetch_add(1, Ordering::SeqCst) + 1) << 2) &
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SPECIAL_STACKING_CONTEXT_ID_MASK
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}
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pub fn combine_id_with_fragment_type(id: usize, fragment_type: FragmentType) -> usize {
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debug_assert_eq!(id & (fragment_type as usize), 0);
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if fragment_type == FragmentType::FragmentBody {
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id
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} else {
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next_special_id() | (fragment_type as usize)
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}
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}
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pub fn node_id_from_clip_id(id: usize) -> Option<usize> {
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if (id & !SPECIAL_STACKING_CONTEXT_ID_MASK) != 0 {
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return Some((id & !3) as usize);
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}
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None
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}
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pub trait DisplayList {
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/// Returns true if this display list contains meaningful content.
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fn is_contentful(&self) -> bool;
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}
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