servo/components/layout_2020/fragment_tree/base_fragment.rs
Martin Robinson e5598590ba
layout: Add line height from preserved segment breaks in quirks mode (#31419)
In quirks mode, preserved segment breaks should add line height to
lines. This matches the behavior of WebKit and Blink, but not Gecko.

This also handles the special-case of `<br>` elements, which are
implemented with preserved segment breaks via `white-space: pre-line`.
This is an implementation detail though because `<br>` has a special
behavior if the line isn't empty -- it doesn't add any line height in
this case.
2024-02-26 17:26:41 +00:00

121 lines
4 KiB
Rust

/* 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 bitflags::bitflags;
use gfx_traits::{combine_id_with_fragment_type, FragmentType};
use serde::Serialize;
use style::dom::OpaqueNode;
use style::selector_parser::PseudoElement;
use crate::layout_debug::DebugId;
/// This data structure stores fields that are common to all non-base
/// Fragment types and should generally be the first member of all
/// concrete fragments.
#[derive(Debug, Serialize)]
pub(crate) struct BaseFragment {
/// A tag which identifies the DOM node and pseudo element of this
/// Fragment's content. If this fragment isn't related to any DOM
/// node at all, the tag will be None.
pub tag: Option<Tag>,
/// An id used to uniquely identify this Fragment in debug builds.
pub debug_id: DebugId,
/// Flags which various information about this fragment used during
/// layout.
pub flags: FragmentFlags,
}
impl BaseFragment {
pub(crate) fn anonymous() -> Self {
BaseFragment {
tag: None,
debug_id: DebugId::new(),
flags: FragmentFlags::empty(),
}
}
/// Returns true if this fragment is non-anonymous and it is for the given
/// OpaqueNode, regardless of the pseudo element.
pub(crate) fn is_for_node(&self, node: OpaqueNode) -> bool {
self.tag.map(|tag| tag.node == node).unwrap_or(false)
}
}
/// Information necessary to construct a new BaseFragment.
#[derive(Clone, Copy, Debug, Serialize)]
pub(crate) struct BaseFragmentInfo {
/// The tag to use for the new BaseFragment.
pub tag: Tag,
/// The flags to use for the new BaseFragment.
pub flags: FragmentFlags,
}
impl BaseFragmentInfo {
pub(crate) fn new_for_node(node: OpaqueNode) -> Self {
Self {
tag: Tag::new(node),
flags: FragmentFlags::empty(),
}
}
}
impl From<BaseFragmentInfo> for BaseFragment {
fn from(info: BaseFragmentInfo) -> Self {
Self {
tag: Some(info.tag),
debug_id: DebugId::new(),
flags: info.flags,
}
}
}
bitflags! {
/// Flags used to track various information about a DOM node during layout.
#[derive(Clone, Copy, Debug, Serialize)]
pub(crate) struct FragmentFlags: u8 {
/// Whether or not the node that created this fragment is a `<body>` element on an HTML document.
const IS_BODY_ELEMENT_OF_HTML_ELEMENT_ROOT = 0b00000001;
/// Whether or not the node that created this Fragment is a `<br>` element.
const IS_BR_ELEMENT = 0b00000010;
}
}
/// A data structure used to hold DOM and pseudo-element information about
/// a particular layout object.
#[derive(Clone, Copy, Debug, Eq, PartialEq, Serialize)]
pub(crate) struct Tag {
pub(crate) node: OpaqueNode,
pub(crate) pseudo: Option<PseudoElement>,
}
impl Tag {
/// Create a new Tag for a non-pseudo element. This is mainly used for
/// matching existing tags, since it does not accept an `info` argument.
pub(crate) fn new(node: OpaqueNode) -> Self {
Tag { node, pseudo: None }
}
/// Create a new Tag for a pseudo element. This is mainly used for
/// matching existing tags, since it does not accept an `info` argument.
pub(crate) fn new_pseudo(node: OpaqueNode, pseudo: Option<PseudoElement>) -> Self {
Tag { node, pseudo }
}
/// Returns true if this tag is for a pseudo element.
pub(crate) fn is_pseudo(&self) -> bool {
self.pseudo.is_some()
}
pub(crate) fn to_display_list_fragment_id(&self) -> u64 {
let fragment_type = match self.pseudo {
Some(PseudoElement::Before) => FragmentType::BeforePseudoContent,
Some(PseudoElement::After) => FragmentType::AfterPseudoContent,
_ => FragmentType::FragmentBody,
};
combine_id_with_fragment_type(self.node.id(), fragment_type) as u64
}
}