diff options
Diffstat (limited to 'servo/components/style/invalidation/element/element_wrapper.rs')
| -rw-r--r-- | servo/components/style/invalidation/element/element_wrapper.rs | 391 |
1 files changed, 391 insertions, 0 deletions
diff --git a/servo/components/style/invalidation/element/element_wrapper.rs b/servo/components/style/invalidation/element/element_wrapper.rs new file mode 100644 index 0000000000..71c3c94daf --- /dev/null +++ b/servo/components/style/invalidation/element/element_wrapper.rs @@ -0,0 +1,391 @@ +/* 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/. */ + +//! A wrapper over an element and a snapshot, that allows us to selector-match +//! against a past state of the element. + +use crate::dom::TElement; +use crate::selector_parser::{AttrValue, NonTSPseudoClass, PseudoElement, SelectorImpl}; +use crate::selector_parser::{Snapshot, SnapshotMap}; +use crate::values::AtomIdent; +use crate::{CaseSensitivityExt, LocalName, Namespace, WeakAtom}; +use dom::ElementState; +use selectors::attr::{AttrSelectorOperation, CaseSensitivity, NamespaceConstraint}; +use selectors::matching::{ElementSelectorFlags, MatchingContext}; +use selectors::{Element, OpaqueElement}; +use std::cell::Cell; +use std::fmt; + +/// In order to compute restyle hints, we perform a selector match against a +/// list of partial selectors whose rightmost simple selector may be sensitive +/// to the thing being changed. We do this matching twice, once for the element +/// as it exists now and once for the element as it existed at the time of the +/// last restyle. If the results of the selector match differ, that means that +/// the given partial selector is sensitive to the change, and we compute a +/// restyle hint based on its combinator. +/// +/// In order to run selector matching against the old element state, we generate +/// a wrapper for the element which claims to have the old state. This is the +/// ElementWrapper logic below. +/// +/// Gecko does this differently for element states, and passes a mask called +/// mStateMask, which indicates the states that need to be ignored during +/// selector matching. This saves an ElementWrapper allocation and an additional +/// selector match call at the expense of additional complexity inside the +/// selector matching logic. This only works for boolean states though, so we +/// still need to take the ElementWrapper approach for attribute-dependent +/// style. So we do it the same both ways for now to reduce complexity, but it's +/// worth measuring the performance impact (if any) of the mStateMask approach. +pub trait ElementSnapshot: Sized { + /// The state of the snapshot, if any. + fn state(&self) -> Option<ElementState>; + + /// If this snapshot contains attribute information. + fn has_attrs(&self) -> bool; + + /// Gets the attribute information of the snapshot as a string. + /// + /// Only for debugging purposes. + fn debug_list_attributes(&self) -> String { + String::new() + } + + /// The ID attribute per this snapshot. Should only be called if + /// `has_attrs()` returns true. + fn id_attr(&self) -> Option<&WeakAtom>; + + /// Whether this snapshot contains the class `name`. Should only be called + /// if `has_attrs()` returns true. + fn has_class(&self, name: &AtomIdent, case_sensitivity: CaseSensitivity) -> bool; + + /// Whether this snapshot represents the part named `name`. Should only be + /// called if `has_attrs()` returns true. + fn is_part(&self, name: &AtomIdent) -> bool; + + /// See Element::imported_part. + fn imported_part(&self, name: &AtomIdent) -> Option<AtomIdent>; + + /// A callback that should be called for each class of the snapshot. Should + /// only be called if `has_attrs()` returns true. + fn each_class<F>(&self, _: F) + where + F: FnMut(&AtomIdent); + + /// The `xml:lang=""` or `lang=""` attribute value per this snapshot. + fn lang_attr(&self) -> Option<AttrValue>; +} + +/// A simple wrapper over an element and a snapshot, that allows us to +/// selector-match against a past state of the element. +#[derive(Clone)] +pub struct ElementWrapper<'a, E> +where + E: TElement, +{ + element: E, + cached_snapshot: Cell<Option<&'a Snapshot>>, + snapshot_map: &'a SnapshotMap, +} + +impl<'a, E> ElementWrapper<'a, E> +where + E: TElement, +{ + /// Trivially constructs an `ElementWrapper`. + pub fn new(el: E, snapshot_map: &'a SnapshotMap) -> Self { + ElementWrapper { + element: el, + cached_snapshot: Cell::new(None), + snapshot_map: snapshot_map, + } + } + + /// Gets the snapshot associated with this element, if any. + pub fn snapshot(&self) -> Option<&'a Snapshot> { + if !self.element.has_snapshot() { + return None; + } + + if let Some(s) = self.cached_snapshot.get() { + return Some(s); + } + + let snapshot = self.snapshot_map.get(&self.element); + debug_assert!(snapshot.is_some(), "has_snapshot lied!"); + + self.cached_snapshot.set(snapshot); + + snapshot + } + + /// Returns the states that have changed since the element was snapshotted. + pub fn state_changes(&self) -> ElementState { + let snapshot = match self.snapshot() { + Some(s) => s, + None => return ElementState::empty(), + }; + + match snapshot.state() { + Some(state) => state ^ self.element.state(), + None => ElementState::empty(), + } + } + + /// Returns the value of the `xml:lang=""` (or, if appropriate, `lang=""`) + /// attribute from this element's snapshot or the closest ancestor + /// element snapshot with the attribute specified. + fn get_lang(&self) -> Option<AttrValue> { + let mut current = self.clone(); + loop { + let lang = match self.snapshot() { + Some(snapshot) if snapshot.has_attrs() => snapshot.lang_attr(), + _ => current.element.lang_attr(), + }; + if lang.is_some() { + return lang; + } + current = current.parent_element()?; + } + } +} + +impl<'a, E> fmt::Debug for ElementWrapper<'a, E> +where + E: TElement, +{ + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + // Ignore other fields for now, can change later if needed. + self.element.fmt(f) + } +} + +impl<'a, E> Element for ElementWrapper<'a, E> +where + E: TElement, +{ + type Impl = SelectorImpl; + + fn match_non_ts_pseudo_class( + &self, + pseudo_class: &NonTSPseudoClass, + context: &mut MatchingContext<Self::Impl>, + ) -> bool { + // Some pseudo-classes need special handling to evaluate them against + // the snapshot. + match *pseudo_class { + // For :link and :visited, we don't actually want to test the + // element state directly. + // + // Instead, we use the `visited_handling` to determine if they + // match. + NonTSPseudoClass::Link => { + return self.is_link() && context.visited_handling().matches_unvisited(); + }, + NonTSPseudoClass::Visited => { + return self.is_link() && context.visited_handling().matches_visited(); + }, + + #[cfg(feature = "gecko")] + NonTSPseudoClass::MozTableBorderNonzero => { + if let Some(snapshot) = self.snapshot() { + if snapshot.has_other_pseudo_class_state() { + return snapshot.mIsTableBorderNonzero(); + } + } + }, + + #[cfg(feature = "gecko")] + NonTSPseudoClass::MozBrowserFrame => { + if let Some(snapshot) = self.snapshot() { + if snapshot.has_other_pseudo_class_state() { + return snapshot.mIsMozBrowserFrame(); + } + } + }, + + #[cfg(feature = "gecko")] + NonTSPseudoClass::MozSelectListBox => { + if let Some(snapshot) = self.snapshot() { + if snapshot.has_other_pseudo_class_state() { + return snapshot.mIsSelectListBox(); + } + } + }, + + // :lang() needs to match using the closest ancestor xml:lang="" or + // lang="" attribtue from snapshots. + NonTSPseudoClass::Lang(ref lang_arg) => { + return self + .element + .match_element_lang(Some(self.get_lang()), lang_arg); + }, + + _ => {}, + } + + let flag = pseudo_class.state_flag(); + if flag.is_empty() { + return self + .element + .match_non_ts_pseudo_class(pseudo_class, context); + } + match self.snapshot().and_then(|s| s.state()) { + Some(snapshot_state) => snapshot_state.intersects(flag), + None => self + .element + .match_non_ts_pseudo_class(pseudo_class, context), + } + } + + fn apply_selector_flags(&self, _flags: ElementSelectorFlags) { + debug_assert!(false, "Shouldn't need selector flags for invalidation"); + } + + fn match_pseudo_element( + &self, + pseudo_element: &PseudoElement, + context: &mut MatchingContext<Self::Impl>, + ) -> bool { + self.element.match_pseudo_element(pseudo_element, context) + } + + fn is_link(&self) -> bool { + match self.snapshot().and_then(|s| s.state()) { + Some(state) => state.intersects(ElementState::VISITED_OR_UNVISITED), + None => self.element.is_link(), + } + } + + fn opaque(&self) -> OpaqueElement { + self.element.opaque() + } + + fn parent_element(&self) -> Option<Self> { + let parent = self.element.parent_element()?; + Some(Self::new(parent, self.snapshot_map)) + } + + fn parent_node_is_shadow_root(&self) -> bool { + self.element.parent_node_is_shadow_root() + } + + fn containing_shadow_host(&self) -> Option<Self> { + let host = self.element.containing_shadow_host()?; + Some(Self::new(host, self.snapshot_map)) + } + + fn prev_sibling_element(&self) -> Option<Self> { + let sibling = self.element.prev_sibling_element()?; + Some(Self::new(sibling, self.snapshot_map)) + } + + fn next_sibling_element(&self) -> Option<Self> { + let sibling = self.element.next_sibling_element()?; + Some(Self::new(sibling, self.snapshot_map)) + } + + fn first_element_child(&self) -> Option<Self> { + let child = self.element.first_element_child()?; + Some(Self::new(child, self.snapshot_map)) + } + + #[inline] + fn is_html_element_in_html_document(&self) -> bool { + self.element.is_html_element_in_html_document() + } + + #[inline] + fn is_html_slot_element(&self) -> bool { + self.element.is_html_slot_element() + } + + #[inline] + fn has_local_name( + &self, + local_name: &<Self::Impl as ::selectors::SelectorImpl>::BorrowedLocalName, + ) -> bool { + self.element.has_local_name(local_name) + } + + #[inline] + fn has_namespace( + &self, + ns: &<Self::Impl as ::selectors::SelectorImpl>::BorrowedNamespaceUrl, + ) -> bool { + self.element.has_namespace(ns) + } + + #[inline] + fn is_same_type(&self, other: &Self) -> bool { + self.element.is_same_type(&other.element) + } + + fn attr_matches( + &self, + ns: &NamespaceConstraint<&Namespace>, + local_name: &LocalName, + operation: &AttrSelectorOperation<&AttrValue>, + ) -> bool { + match self.snapshot() { + Some(snapshot) if snapshot.has_attrs() => { + snapshot.attr_matches(ns, local_name, operation) + }, + _ => self.element.attr_matches(ns, local_name, operation), + } + } + + fn has_id(&self, id: &AtomIdent, case_sensitivity: CaseSensitivity) -> bool { + match self.snapshot() { + Some(snapshot) if snapshot.has_attrs() => snapshot + .id_attr() + .map_or(false, |atom| case_sensitivity.eq_atom(&atom, id)), + _ => self.element.has_id(id, case_sensitivity), + } + } + + fn is_part(&self, name: &AtomIdent) -> bool { + match self.snapshot() { + Some(snapshot) if snapshot.has_attrs() => snapshot.is_part(name), + _ => self.element.is_part(name), + } + } + + fn imported_part(&self, name: &AtomIdent) -> Option<AtomIdent> { + match self.snapshot() { + Some(snapshot) if snapshot.has_attrs() => snapshot.imported_part(name), + _ => self.element.imported_part(name), + } + } + + fn has_class(&self, name: &AtomIdent, case_sensitivity: CaseSensitivity) -> bool { + match self.snapshot() { + Some(snapshot) if snapshot.has_attrs() => snapshot.has_class(name, case_sensitivity), + _ => self.element.has_class(name, case_sensitivity), + } + } + + fn is_empty(&self) -> bool { + self.element.is_empty() + } + + fn is_root(&self) -> bool { + self.element.is_root() + } + + fn is_pseudo_element(&self) -> bool { + self.element.is_pseudo_element() + } + + fn pseudo_element_originating_element(&self) -> Option<Self> { + self.element + .pseudo_element_originating_element() + .map(|e| ElementWrapper::new(e, self.snapshot_map)) + } + + fn assigned_slot(&self) -> Option<Self> { + self.element + .assigned_slot() + .map(|e| ElementWrapper::new(e, self.snapshot_map)) + } +} |