chromium/third_party/blink/renderer/core/css/invalidation/rule_invalidation_data.h

// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_CSS_INVALIDATION_RULE_INVALIDATION_DATA_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_INVALIDATION_RULE_INVALIDATION_DATA_H_

#include "third_party/blink/renderer/core/css/css_selector.h"
#include "third_party/blink/renderer/core/css/invalidation/invalidation_set.h"
#include "third_party/blink/renderer/platform/wtf/bloom_filter.h"
#include "third_party/blink/renderer/platform/wtf/hash_map.h"
#include "third_party/blink/renderer/platform/wtf/text/atomic_string.h"

namespace blink {

enum class RuleInvalidationDataVisitorType;

// Summarizes and indexes the contents of CSS selectors. It creates
// invalidation sets from them and makes them available via several
// CollectInvalidationSetForFoo methods which use the indices to quickly gather
// the relevant InvalidationSets for a particular DOM mutation.
// Also captures several pieces of metadata that describe the entire set of
// indexed selectors, for example "does any selector use ::first-line".
//
// In addition to complete invalidation (where we just throw up our
// hands and invalidate everything) and :has() (which is described in
// detail below), we have fundamentally four types of invalidation.
// All will be described for a class selector, but apply equally to
// id etc.:
//
//   - Self-invalidation: When an element gets or loses class .c,
//     that element needs to be invalidated (.c exists as a subject in
//     some selector). We represent this by a bit in .c's invalidation
//     set (or by inserting the class name in a Bloom filter; see
//     class_invalidation_sets_).
//
//   - Descendant invalidation: When an element gets or loses class .c,
//     all of its children with class .d need to be invalidated
//     (a selector of the form .c .d or .c > .d exists). We represent
//     this by storing .d in .c's descendant invalidation set.
//
//   - Sibling invalidation: When an element gets or loses class .c,
//     all of its _siblings_ with class .d need to be invalidated
//     (a selector of the form .c ~ .d or .c + .d exists).
//     We represent this by storing .d in c's sibling invalidation set.
//
//   - nth-child invalidation: Described immediately below.
//
// nth-child invalidation deals with peculiarities for :nth-child()
// and related selectors (such as :only-of-type). We have a couple
// of distinct strategies for dealing with them:
//
//   - When we add or insert a node in the DOM tree where any child
//     of the parent has matched such a selector, we forcibly schedule
//     the (global) NthSiblingInvalidationSet. In other words, this
//     is hardly related to the normal invalidation mechanism at all.
//
//   - Finally, for :nth_child(... of :has()), we get a signal when
//     a node is affected by :has() subject invalidation
//     (in StyleEngine::InvalidateElementAffectedByHas()), and can
//     forcibly schedule the NthSiblingInvalidationSet, much like
//     the previous point.
//
//   - When we have :nth-child(... of S) as a subject (ie., not just
//     pure :nth-child(), but anything with a selector), we set the
//     invalidates_nth_ bit on all invalidation sets for S. This means
//     that whenever we schedule invalidation sets for anything in S,
//     and any child of the parent has matched any :nth-child() selector,
//     we'll schedule the NthSiblingInvalidationSet.
//
//   - For all ancestors, we go through them recursively to find
//     S within :nth-child(), and set their invalidates_nth_ similarly.
//     This is conceptually the same thing as the previous point,
//     but since we already handle subjects and ancestors differently,
//     it was convenient with some mild code duplication here.
//
//   - When we have sibling selectors against :nth-child, special
//     provisions apply; see comments NthSiblingInvalidationSet.
class CORE_EXPORT RuleInvalidationData { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_INVALIDATION_RULE_INVALIDATION_DATA_H_