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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 */
/* the interface (to internal code) for retrieving computed style data */
#ifndef _ComputedStyle_h_
#define _ComputedStyle_h_
#include "mozilla/Assertions.h"
#include "mozilla/CachedInheritingStyles.h"
#include "mozilla/Maybe.h"
#include "mozilla/PseudoStyleType.h"
#include "mozilla/ServoComputedData.h"
#include "mozilla/ServoStyleConsts.h"
#include "nsCSSPseudoElements.h"
#include "nsColor.h"
#include "nsStyleStructFwd.h"
enum nsChangeHint : uint32_t;
class nsWindowSizes;
#define STYLE_STRUCT(name_) struct nsStyle##name_;
#include "nsStyleStructList.h"
extern "C" {
void Gecko_ComputedStyle_Destroy(mozilla::ComputedStyle*);
namespace mozilla {
enum class StylePointerEvents : uint8_t;
enum class StyleUserSelect : uint8_t;
namespace dom {
class Document;
* A ComputedStyle represents the computed style data for an element.
* The computed style data are stored in a set of reference counted structs
* (see nsStyleStruct.h) that are stored directly on the ComputedStyle.
* Style structs are immutable once they have been produced, so when any change
* is made that needs a restyle, we create a new ComputedStyle.
* ComputedStyles are reference counted. References are generally held by:
* 1. nsIFrame::mComputedStyle, for every frame
* 2. Element::mServoData, for every element not inside a display:none subtree
* 3. nsComputedDOMStyle, when created for elements in display:none subtrees
* 4. media_queries::Device, which holds the initial value of every property
class ComputedStyle {
using Flag = StyleComputedValueFlags;
const StyleComputedValueFlags& Flags() const { return mSource.flags; }
ComputedStyle(PseudoStyleType aPseudoType,
ServoComputedDataForgotten aComputedValues);
// Returns the computed (not resolved) value of the given property.
void GetComputedPropertyValue(nsCSSPropertyID aId, nsACString& aOut) const {
Servo_GetComputedValue(this, aId, &aOut);
// Return the ComputedStyle whose style data should be used for the R,
// G, and B components of color, background-color, and border-*-color
// if RelevantLinkIsVisited().
// GetPseudo() and GetPseudoType() on this ComputedStyle return the
// same as on |this|, and its depth in the tree (number of GetParent()
// calls until null is returned) is the same as |this|, since its
// parent is either |this|'s parent or |this|'s parent's
// style-if-visited.
// Structs on this context should never be examined without also
// examining the corresponding struct on |this|. Doing so will likely
// both (1) lead to a privacy leak and (2) lead to dynamic change bugs
// related to the Peek code in ComputedStyle::CalcStyleDifference.
const ComputedStyle* GetStyleIfVisited() const {
return mSource.visited_style;
bool IsLazilyCascadedPseudoElement() const {
return IsPseudoElement() &&
PseudoStyleType GetPseudoType() const { return mPseudoType; }
bool IsPseudoElement() const {
return PseudoStyle::IsPseudoElement(mPseudoType);
bool IsInheritingAnonBox() const {
return PseudoStyle::IsInheritingAnonBox(mPseudoType);
bool IsNonInheritingAnonBox() const {
return PseudoStyle::IsNonInheritingAnonBox(mPseudoType);
bool IsWrapperAnonBox() const {
return PseudoStyle::IsWrapperAnonBox(mPseudoType);
bool IsAnonBox() const { return PseudoStyle::IsAnonBox(mPseudoType); }
bool IsPseudoOrAnonBox() const {
return mPseudoType != PseudoStyleType::NotPseudo;
// Whether there are author-specified rules for border or background
// properties.
// Only returns something meaningful if the appearance property is not `none`.
bool HasAuthorSpecifiedBorderOrBackground() const {
// Whether there are author-specific rules for text color.
bool HasAuthorSpecifiedTextColor() const {
return bool(Flags() & Flag::HAS_AUTHOR_SPECIFIED_TEXT_COLOR);
// Does this ComputedStyle or any of its ancestors have text
// decoration lines?
// Differs from nsStyleTextReset::HasTextDecorationLines, which tests
// only the data for a single context.
bool HasTextDecorationLines() const {
return bool(Flags() & Flag::HAS_TEXT_DECORATION_LINES);
// Whether any line break inside should be suppressed? If this returns
// true, the line should not be broken inside, which means inlines act
// as if nowrap is set, <br> is suppressed, and blocks are inlinized.
// This bit is propogated to all children of line partitipants. It is
// currently used by ruby to make its content frames unbreakable.
// NOTE: for nsTextFrame, use nsTextFrame::ShouldSuppressLineBreak()
// instead of this method.
bool ShouldSuppressLineBreak() const {
return bool(Flags() & Flag::SHOULD_SUPPRESS_LINEBREAK);
// Is this horizontal-in-vertical (tate-chu-yoko) text? This flag is
// only set on ComputedStyles whose pseudo is nsCSSAnonBoxes::mozText().
bool IsTextCombined() const { return bool(Flags() & Flag::IS_TEXT_COMBINED); }
// Whether there's any font metric dependency coming directly from our style.
bool DependsOnSelfFontMetrics() const {
return bool(Flags() & Flag::DEPENDS_ON_SELF_FONT_METRICS);
// Whether there's any font metric dependency coming directly from our parent
// style.
bool DependsOnInheritedFontMetrics() const {
return bool(Flags() & Flag::DEPENDS_ON_INHERITED_FONT_METRICS);
// Does this ComputedStyle represent the style for a pseudo-element or
// inherit data from such a ComputedStyle? Whether this returns true
// is equivalent to whether it or any of its ancestors returns
// non-null for IsPseudoElement().
bool HasPseudoElementData() const {
return bool(Flags() & Flag::IS_IN_PSEUDO_ELEMENT_SUBTREE);
bool SelfOrAncestorHasContainStyle() const {
return bool(Flags() & Flag::SELF_OR_ANCESTOR_HAS_CONTAIN_STYLE);
// Is the only link whose visitedness is allowed to influence the
// style of the node this ComputedStyle is for (which is that element
// or its nearest ancestor that is a link) visited?
bool RelevantLinkVisited() const {
return bool(Flags() & Flag::IS_RELEVANT_LINK_VISITED);
// Whether this style is for the root element of the document.
bool IsRootElementStyle() const {
return bool(Flags() & Flag::IS_ROOT_ELEMENT_STYLE);
bool IsInOpacityZeroSubtree() const {
return bool(Flags() & Flag::IS_IN_OPACITY_ZERO_SUBTREE);
ComputedStyle* GetCachedInheritingAnonBoxStyle(
PseudoStyleType aPseudoType) const {
return mCachedInheritingStyles.Lookup(aPseudoType);
void SetCachedInheritedAnonBoxStyle(ComputedStyle* aStyle) {
ComputedStyle* GetCachedLazyPseudoStyle(PseudoStyleType aPseudo) const;
void SetCachedLazyPseudoStyle(ComputedStyle* aStyle) {
// Since we're caching lazy pseudo styles on the ComputedValues of the
// originating element, we can assume that we either have the same
// originating element, or that they were at least similar enough to share
// the same ComputedValues, which means that they would match the same
// pseudo rules. This allows us to avoid matching selectors and checking
// the rule node before deciding to share.
// The one place this optimization breaks is with pseudo-elements that
// support state (like :hover). So we just avoid sharing in those cases.
if (nsCSSPseudoElements::PseudoElementSupportsUserActionState(
aStyle->GetPseudoType())) {
#define STYLE_STRUCT(name_) \
inline const nsStyle##name_* Style##name_() const MOZ_NONNULL_RETURN { \
return mSource.Style##name_(); \
#include "nsStyleStructList.h"
inline mozilla::StylePointerEvents PointerEvents() const;
inline mozilla::StyleUserSelect UserSelect() const;
* Returns whether the element is a containing block for its absolutely
* positioned descendants.
* aContextFrame is the frame for which this is the style (or an old style).
inline bool IsAbsPosContainingBlock(const nsIFrame*) const;
* Returns true when the element is a containing block for its fixed-pos
* descendants.
* aContextFrame is the frame for which this is the style (or an old style).
inline bool IsFixedPosContainingBlock(const nsIFrame*) const;
* Tests for only the sub-parts of IsFixedPosContainingBlock that apply to:
* - nearly all frames, except those that are in SVG text subtrees.
* - frames that support CSS contain:layout and contain:paint and are not
* in SVG text subtrees.
* - frames that support CSS transforms and are not in SVG text subtrees.
* This should be used only when the caller has the style but not the
* frame (i.e., when calculating style changes).
inline bool IsFixedPosContainingBlockForNonSVGTextFrames() const;
* Compute the style changes needed during restyling when this style
* context is being replaced by aNewContext. (This is nonsymmetric since
* we optimize by skipping comparison for styles that have never been
* requested.)
* This method returns a change hint (see nsChangeHint.h). All change
* hints apply to the frame and its later continuations or ib-split
* siblings. Most (all of those except the "NotHandledForDescendants"
* hints) also apply to all descendants.
* aEqualStructs must not be null. Into it will be stored a bitfield
* representing which structs were compared to be non-equal.
* CSS Variables are not compared here. Instead, the caller is responsible for
* that when needed (basically only for elements).
nsChangeHint CalcStyleDifference(const ComputedStyle& aNewContext,
uint32_t* aEqualStructs) const;
#ifdef DEBUG
bool EqualForCachedAnonymousContentStyle(const ComputedStyle&) const;
#ifdef DEBUG
void DumpMatchedRules() const;
* Get a color that depends on link-visitedness using this and
* this->GetStyleIfVisited().
* @param aField A pointer to a member variable in a style struct.
* The member variable and its style struct must have
* been listed in nsCSSVisitedDependentPropList.h.
template <typename T, typename S>
nscolor GetVisitedDependentColor(T S::*aField) const;
* aColors should be a two element array of nscolor in which the first
* color is the unvisited color and the second is the visited color.
* Combine the R, G, and B components of whichever of aColors should
* be used based on aLinkIsVisited with the A component of aColors[0].
static nscolor CombineVisitedColors(nscolor* aColors, bool aLinkIsVisited);
* Start image loads for this style.
* The Document is used to get a hand on the image loader. The old style is a
* hack for bug 1439285.
inline void StartImageLoads(dom::Document&,
const ComputedStyle* aOldStyle = nullptr);
#ifdef DEBUG
void List(FILE* out, int32_t aIndent);
static const char* StructName(StyleStructID aSID);
static Maybe<StyleStructID> LookupStruct(const nsACString& aName);
// The |aCVsSize| outparam on this function is where the actual CVs size
// value is added. It's done that way because the callers know which value
// the size should be added to.
void AddSizeOfIncludingThis(nsWindowSizes& aSizes, size_t* aCVsSize) const;
StyleWritingMode WritingMode() const { return {mSource.WritingMode().mBits}; }
const StyleZoom& EffectiveZoom() const { return mSource.effective_zoom; }
// Needs to be friend so that it can call the destructor without making it
// public.
friend void ::Gecko_ComputedStyle_Destroy(ComputedStyle*);
~ComputedStyle() = default;
ServoComputedData mSource;
// A cache of anonymous box and lazy pseudo styles inheriting from this style.
CachedInheritingStyles mCachedInheritingStyles;
const PseudoStyleType mPseudoType;
} // namespace mozilla