cascade_priority.h | Explore in Territory

// Copyright 2020 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_RESOLVER_CASCADE_PRIORITY_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_RESOLVER_CASCADE_PRIORITY_H_

#include "base/check_op.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/css/resolver/cascade_origin.h"

namespace blink {

// The origin and importance criteria are evaluated together [1], hence we
// encode both into a single integer which will do the right thing when compared
// to another such encoded integer. See CascadeOrigin for more information on
// how that works.
//
// [1] https://www.w3.org/TR/css-cascade-3/#cascade-origin
inline uint32_t EncodeOriginImportance(CascadeOrigin origin, bool important) { … }

// Tree order bits are flipped for important declarations to reverse the
// priority [1].
//
// [1] https://drafts.csswg.org/css-scoping/#shadow-cascading
inline uint32_t EncodeTreeOrder(uint16_t tree_order, bool important) { … }

// Layer order bits are flipped for important declarations to reverse the
// priority [1].
//
// [1] https://drafts.csswg.org/css-cascade-5/#cascade-layering
inline uint64_t EncodeLayerOrder(uint16_t layer_order, bool important) { … }

// The CascadePriority class encapsulates a subset of the cascading criteria
// described by css-cascade [1], and provides a way to compare priorities
// quickly by encoding all the information in a single integer.
//
// It encompasses, from most significant to least significant:
// Origin/importance; tree order, which is a number representing the
// shadow-including tree order [2]; inline style, which is a boolean incidating
// whether the declaration is in the style attribute [3]; layer order, which is
// a number representing the cascade layer order in the origin and tree scope
// [4]; position, which contains the index (or indices) required to lookup a
// declaration in the underlying structure (e.g. a MatchResult); and finally
// generation, which is a monotonically increasing number generated by
// StyleCascade for each call to StyleCascade::Apply.
//
// [1] https://drafts.csswg.org/css-cascade/#cascading
// [2] https://drafts.csswg.org/css-scoping/#shadow-cascading
// [3] https://drafts.csswg.org/css-cascade/#style-attr
// [4] https://drafts.csswg.org/css-cascade-5/#layer-ordering
class CORE_EXPORT CascadePriority { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_RESOLVER_CASCADE_PRIORITY_H_
chromium/third_party/blink/renderer/core/css/resolver/cascade_priority.h
