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gecko-dev/layout/style/nsStyleContext.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 http://mozilla.org/MPL/2.0/. */
/* the interface (to internal code) for retrieving computed style data */
#ifndef _nsStyleContext_h_
#define _nsStyleContext_h_
#include "mozilla/Assertions.h"
#include "mozilla/RestyleLogging.h"
#include "mozilla/StyleContextSource.h"
#include "mozilla/StyleComplexColor.h"
#include "nsCSSAnonBoxes.h"
#include "nsStyleSet.h"
class nsIAtom;
class nsPresContext;
namespace mozilla {
enum class CSSPseudoElementType : uint8_t;
} // namespace mozilla
extern "C" {
#define STYLE_STRUCT(name_, checkdata_cb_) \
struct nsStyle##name_; \
const nsStyle##name_* Servo_GetStyle##name_( \
ServoComputedValuesBorrowedOrNull computed_values);
#include "nsStyleStructList.h"
#undef STYLE_STRUCT
}
/**
* An nsStyleContext represents the computed style data for an element.
* The computed style data are stored in a set of structs (see
* nsStyleStruct.h) that are cached either on the style context or in
* the rule tree (see nsRuleNode.h for a description of this caching and
* how the cached structs are shared).
*
* Since the data in |nsIStyleRule|s and |nsRuleNode|s are immutable
* (with a few exceptions, like system color changes), the data in an
* nsStyleContext are also immutable (with the additional exception of
* GetUniqueStyleData). When style data change,
* ElementRestyler::Restyle creates a new style context.
*
* Style contexts are reference counted. References are generally held
* by:
* 1. the |nsIFrame|s that are using the style context and
* 2. any *child* style contexts (this might be the reverse of
* expectation, but it makes sense in this case)
*/
class nsStyleContext final
{
public:
/**
* Create a new style context.
* @param aParent The parent of a style context is used for CSS
* inheritance. When the element or pseudo-element
* this style context represents the style data of
* inherits a CSS property, the value comes from the
* parent style context. This means style context
* parentage must match the definitions of inheritance
* in the CSS specification.
* @param aPseudoTag The pseudo-element or anonymous box for which
* this style context represents style. Null if
* this style context is for a normal DOM element.
* @param aPseudoType Must match aPseudoTag.
* @param aRuleNode A rule node representing the ordered sequence of
* rules that any element, pseudo-element, or
* anonymous box that this style context is for
* matches. See |nsRuleNode| and |nsIStyleRule|.
* @param aSkipParentDisplayBasedStyleFixup
* If set, this flag indicates that we should skip
* the chunk of ApplyStyleFixups() that applies to
* special cases where a child element's style may
* need to be modified based on its parent's display
* value.
*/
nsStyleContext(nsStyleContext* aParent, nsIAtom* aPseudoTag,
mozilla::CSSPseudoElementType aPseudoType,
already_AddRefed<nsRuleNode> aRuleNode,
bool aSkipParentDisplayBasedStyleFixup);
// Version of the above that takes a ServoComputedValues instead of a Gecko
// nsRuleNode.
nsStyleContext(nsStyleContext* aParent,
nsPresContext* aPresContext,
nsIAtom* aPseudoTag,
mozilla::CSSPseudoElementType aPseudoType,
already_AddRefed<ServoComputedValues> aComputedValues,
bool aSkipParentDisplayBasedStyleFixup);
void* operator new(size_t sz, nsPresContext* aPresContext);
void Destroy();
// These two methods are for use by ArenaRefPtr.
static mozilla::ArenaObjectID ArenaObjectID()
{
return mozilla::eArenaObjectID_nsStyleContext;
}
nsIPresShell* Arena();
#ifdef DEBUG
/**
* Initializes a cached pref, which is only used in DEBUG code.
*/
static void Initialize();
#endif
nsrefcnt AddRef() {
if (mRefCnt == UINT32_MAX) {
NS_WARNING("refcount overflow, leaking object");
return mRefCnt;
}
++mRefCnt;
NS_LOG_ADDREF(this, mRefCnt, "nsStyleContext", sizeof(nsStyleContext));
return mRefCnt;
}
nsrefcnt Release() {
if (mRefCnt == UINT32_MAX) {
NS_WARNING("refcount overflow, leaking object");
return mRefCnt;
}
--mRefCnt;
NS_LOG_RELEASE(this, mRefCnt, "nsStyleContext");
if (mRefCnt == 0) {
Destroy();
return 0;
}
return mRefCnt;
}
#ifdef DEBUG
void FrameAddRef() {
++mFrameRefCnt;
}
void FrameRelease() {
--mFrameRefCnt;
}
uint32_t FrameRefCnt() const {
return mFrameRefCnt;
}
#endif
bool HasSingleReference() const {
NS_ASSERTION(mRefCnt != 0,
"do not call HasSingleReference on a newly created "
"nsStyleContext with no references yet");
return mRefCnt == 1;
}
nsPresContext* PresContext() const {
#ifdef MOZ_STYLO
return mPresContext;
#else
return mSource.AsGeckoRuleNode()->PresContext();
#endif
}
nsStyleContext* GetParent() const { return mParent; }
nsIAtom* GetPseudo() const { return mPseudoTag; }
mozilla::CSSPseudoElementType GetPseudoType() const {
return static_cast<mozilla::CSSPseudoElementType>(
mBits >> NS_STYLE_CONTEXT_TYPE_SHIFT);
}
bool IsAnonBox() const {
return GetPseudoType() == mozilla::CSSPseudoElementType::AnonBox;
}
bool IsPseudoElement() const { return mPseudoTag && !IsAnonBox(); }
// Find, if it already exists *and is easily findable* (i.e., near the
// start of the child list), a style context whose:
// * GetPseudo() matches aPseudoTag
// * mSource matches aSource
// * !!GetStyleIfVisited() == !!aSourceIfVisited, and, if they're
// non-null, GetStyleIfVisited()->mSource == aSourceIfVisited
// * RelevantLinkVisited() == aRelevantLinkVisited
already_AddRefed<nsStyleContext>
FindChildWithRules(const nsIAtom* aPseudoTag,
mozilla::NonOwningStyleContextSource aSource,
mozilla::NonOwningStyleContextSource aSourceIfVisited,
bool aRelevantLinkVisited);
// Does this style context 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 !!(mBits & NS_STYLE_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 !!(mBits & NS_STYLE_SUPPRESS_LINEBREAK); }
// Does this style context or any of its ancestors have display:none set?
bool IsInDisplayNoneSubtree() const
{ return !!(mBits & NS_STYLE_IN_DISPLAY_NONE_SUBTREE); }
// Is this horizontal-in-vertical (tate-chu-yoko) text? This flag is
// only set on style contexts whose pseudo is nsCSSAnonBoxes::mozText.
bool IsTextCombined() const
{ return !!(mBits & NS_STYLE_IS_TEXT_COMBINED); }
// Does this style context represent the style for a pseudo-element or
// inherit data from such a style context? Whether this returns true
// is equivalent to whether it or any of its ancestors returns
// non-null for IsPseudoElement().
bool HasPseudoElementData() const
{ return !!(mBits & NS_STYLE_HAS_PSEUDO_ELEMENT_DATA); }
bool HasChildThatUsesResetStyle() const
{ return mBits & NS_STYLE_HAS_CHILD_THAT_USES_RESET_STYLE; }
// Is the only link whose visitedness is allowed to influence the
// style of the node this style context is for (which is that element
// or its nearest ancestor that is a link) visited?
bool RelevantLinkVisited() const
{ return !!(mBits & NS_STYLE_RELEVANT_LINK_VISITED); }
// Is this a style context for a link?
bool IsLinkContext() const {
return
GetStyleIfVisited() && GetStyleIfVisited()->GetParent() == GetParent();
}
// Is this style context the GetStyleIfVisited() for some other style
// context?
bool IsStyleIfVisited() const
{ return !!(mBits & NS_STYLE_IS_STYLE_IF_VISITED); }
// Tells this style context that it should return true from
// IsStyleIfVisited.
void SetIsStyleIfVisited()
{ mBits |= NS_STYLE_IS_STYLE_IF_VISITED; }
// Return the style context 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 style context 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 nsStyleContext::CalcStyleDifference.
nsStyleContext* GetStyleIfVisited() const
{ return mStyleIfVisited; }
// To be called only from nsStyleSet.
void SetStyleIfVisited(already_AddRefed<nsStyleContext> aStyleIfVisited)
{
MOZ_ASSERT(!IsStyleIfVisited(), "this context is not visited data");
NS_ASSERTION(!mStyleIfVisited, "should only be set once");
mStyleIfVisited = aStyleIfVisited;
MOZ_ASSERT(mStyleIfVisited->IsStyleIfVisited(),
"other context is visited data");
MOZ_ASSERT(!mStyleIfVisited->GetStyleIfVisited(),
"other context does not have visited data");
NS_ASSERTION(GetStyleIfVisited()->GetPseudo() == GetPseudo(),
"pseudo tag mismatch");
if (GetParent() && GetParent()->GetStyleIfVisited()) {
NS_ASSERTION(GetStyleIfVisited()->GetParent() ==
GetParent()->GetStyleIfVisited() ||
GetStyleIfVisited()->GetParent() == GetParent(),
"parent mismatch");
} else {
NS_ASSERTION(GetStyleIfVisited()->GetParent() == GetParent(),
"parent mismatch");
}
}
// Does any descendant of this style context have any style values
// that were computed based on this style context's ancestors?
bool HasChildThatUsesGrandancestorStyle() const
{ return !!(mBits & NS_STYLE_CHILD_USES_GRANDANCESTOR_STYLE); }
// Is this style context shared with a sibling or cousin?
// (See nsStyleSet::GetContext.)
bool IsShared() const
{ return !!(mBits & NS_STYLE_IS_SHARED); }
// Tell this style context to cache aStruct as the struct for aSID
void SetStyle(nsStyleStructID aSID, void* aStruct);
/**
* Returns whether this style context has cached style data for a
* given style struct and it does NOT own that struct. This can
* happen because it was inherited from the parent style context, or
* because it was stored conditionally on the rule node.
*/
bool HasCachedDependentStyleData(nsStyleStructID aSID) {
return mBits & nsCachedStyleData::GetBitForSID(aSID);
}
nsRuleNode* RuleNode() {
MOZ_RELEASE_ASSERT(mSource.IsGeckoRuleNode());
return mSource.AsGeckoRuleNode();
}
void AddStyleBit(const uint64_t& aBit) { mBits |= aBit; }
/*
* Get the style data for a style struct. This is the most important
* member function of nsStyleContext. It fills in a const pointer
* to a style data struct that is appropriate for the style context's
* frame. This struct may be shared with other contexts (either in
* the rule tree or the style context tree), so it should not be
* modified.
*
* This function will NOT return null (even when out of memory) when
* given a valid style struct ID, so the result does not need to be
* null-checked.
*
* The typesafe functions below are preferred to the use of this
* function, both because they're easier to read and because they're
* faster.
*/
const void* NS_FASTCALL StyleData(nsStyleStructID aSID);
/**
* Define typesafe getter functions for each style struct by
* preprocessing the list of style structs. These functions are the
* preferred way to get style data. The macro creates functions like:
* const nsStyleBorder* StyleBorder();
* const nsStyleColor* StyleColor();
*/
#define STYLE_STRUCT(name_, checkdata_cb_) \
const nsStyle##name_ * Style##name_() { \
return DoGetStyle##name_<true>(); \
}
#include "nsStyleStructList.h"
#undef STYLE_STRUCT
/**
* PeekStyle* is like Style* but doesn't trigger style
* computation if the data is not cached on either the style context
* or the rule node.
*
* Perhaps this shouldn't be a public nsStyleContext API.
*/
#define STYLE_STRUCT(name_, checkdata_cb_) \
const nsStyle##name_ * PeekStyle##name_() { \
return DoGetStyle##name_<false>(); \
}
#include "nsStyleStructList.h"
#undef STYLE_STRUCT
/**
* 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. The caller must pass in any
* non-inherited hints that resulted from the parent style context's
* style change. The caller *may* pass more hints than needed, but
* must not pass less than needed; therefore if the caller doesn't
* know, the caller should pass
* nsChangeHint_Hints_NotHandledForDescendants.
*
* aEqualStructs must not be null. Into it will be stored a bitfield
* representing which structs were compared to be non-equal.
*/
nsChangeHint CalcStyleDifference(nsStyleContext* aNewContext,
nsChangeHint aParentHintsNotHandledForDescendants,
uint32_t* aEqualStructs,
uint32_t* aSamePointerStructs);
/**
* Like the above, but allows comparing ServoComputedValues instead of needing
* a full-fledged style context.
*/
nsChangeHint CalcStyleDifference(const ServoComputedValues* aNewComputedValues,
nsChangeHint aParentHintsNotHandledForDescendants,
uint32_t* aEqualStructs,
uint32_t* aSamePointerStructs);
private:
enum class NeutralChangeHandling {
Retain,
Strip,
};
template<class StyleContextLike, NeutralChangeHandling aNeutralChangeHandling>
nsChangeHint CalcStyleDifferenceInternal(StyleContextLike* aNewContext,
nsChangeHint aParentHintsNotHandledForDescendants,
uint32_t* aEqualStructs,
uint32_t* aSamePointerStructs);
public:
/**
* 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);
/**
* 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 the background image loads for this style context.
*/
void StartBackgroundImageLoads() {
// Just get our background struct; that should do the trick
StyleBackground();
}
/**
* Moves this style context to a new parent.
*
* This function violates style context tree immutability, and
* is a very low-level function and should only be used after verifying
* many conditions that make it safe to call.
*/
void MoveTo(nsStyleContext* aNewParent);
/**
* Swaps owned style struct pointers between this and aNewContext, on
* the assumption that aNewContext is the new style context for a frame
* and this is the old one. aStructs indicates which structs to consider
* swapping; only those which are owned in both this and aNewContext
* will be swapped.
*
* Additionally, if there are identical struct pointers for one of the
* structs indicated by aStructs, and it is not an owned struct on this,
* then the cached struct slot on this will be set to null. If the struct
* has been swapped on an ancestor, this style context (being the old one)
* will be left caching the struct pointer on the new ancestor, despite
* inheriting from the old ancestor. This is not normally a problem, as
* this style context will usually be destroyed by being released at the
* end of ElementRestyler::Restyle; but for style contexts held on to outside
* of the frame, we need to clear out the cached pointer so that if we need
* it again we'll re-fetch it from the new ancestor.
*/
void SwapStyleData(nsStyleContext* aNewContext, uint32_t aStructs);
/**
* On each descendant of this style context, clears out any cached inherited
* structs indicated in aStructs.
*/
void ClearCachedInheritedStyleDataOnDescendants(uint32_t aStructs);
/**
* Sets the NS_STYLE_INELIGIBLE_FOR_SHARING bit on this style context
* and its descendants. If it finds a descendant that has the bit
* already set, assumes that it can skip that subtree.
*/
void SetIneligibleForSharing();
#ifdef DEBUG
void List(FILE* out, int32_t aIndent, bool aListDescendants = true);
static void AssertStyleStructMaxDifferenceValid();
static const char* StructName(nsStyleStructID aSID);
static bool LookupStruct(const nsACString& aName, nsStyleStructID& aResult);
#endif
#ifdef RESTYLE_LOGGING
nsCString GetCachedStyleDataAsString(uint32_t aStructs);
void LogStyleContextTree(int32_t aLoggingDepth, uint32_t aStructs);
int32_t& LoggingDepth();
#endif
/**
* Return style data that is currently cached on the style context.
* Only returns the structs we cache ourselves; never consults the
* rule tree.
*
* For "internal" use only in nsStyleContext and nsRuleNode.
*/
const void* GetCachedStyleData(nsStyleStructID aSID)
{
const void* cachedData;
if (nsCachedStyleData::IsReset(aSID)) {
if (mCachedResetData) {
cachedData = mCachedResetData->mStyleStructs[aSID];
} else {
cachedData = nullptr;
}
} else {
cachedData = mCachedInheritedData.mStyleStructs[aSID];
}
return cachedData;
}
mozilla::NonOwningStyleContextSource StyleSource() const { return mSource.AsRaw(); }
private:
// Private destructor, to discourage deletion outside of Release():
~nsStyleContext();
// Delegated Helper constructor.
nsStyleContext(nsStyleContext* aParent,
mozilla::OwningStyleContextSource&& aSource,
nsIAtom* aPseudoTag,
mozilla::CSSPseudoElementType aPseudoType);
// Helper post-contruct hook.
void FinishConstruction(bool aSkipParentDisplayBasedStyleFixup);
void AddChild(nsStyleContext* aChild);
void RemoveChild(nsStyleContext* aChild);
void* GetUniqueStyleData(const nsStyleStructID& aSID);
void* CreateEmptyStyleData(const nsStyleStructID& aSID);
void SetStyleBits();
void ApplyStyleFixups(bool aSkipParentDisplayBasedStyleFixup);
const void* StyleStructFromServoComputedValues(nsStyleStructID aSID) {
switch (aSID) {
#define STYLE_STRUCT(name_, checkdata_cb_) \
case eStyleStruct_##name_: \
return Servo_GetStyle##name_(mSource.AsServoComputedValues());
#include "nsStyleStructList.h"
#undef STYLE_STRUCT
default:
MOZ_ASSERT_UNREACHABLE("unexpected nsStyleStructID value");
return nullptr;
}
}
#ifdef DEBUG
struct AutoCheckDependency {
nsStyleContext* mStyleContext;
nsStyleStructID mOuterSID;
AutoCheckDependency(nsStyleContext* aContext, nsStyleStructID aInnerSID)
: mStyleContext(aContext)
{
mOuterSID = aContext->mComputingStruct;
MOZ_ASSERT(mOuterSID == nsStyleStructID_None ||
DependencyAllowed(mOuterSID, aInnerSID),
"Undeclared dependency, see generate-stylestructlist.py");
aContext->mComputingStruct = aInnerSID;
}
~AutoCheckDependency()
{
mStyleContext->mComputingStruct = mOuterSID;
}
};
#define AUTO_CHECK_DEPENDENCY(sid_) \
AutoCheckDependency checkNesting_(this, sid_)
#else
#define AUTO_CHECK_DEPENDENCY(sid_)
#endif
// Helper functions for GetStyle* and PeekStyle*
#define STYLE_STRUCT_INHERITED(name_, checkdata_cb_) \
template<bool aComputeData> \
const nsStyle##name_ * DoGetStyle##name_() { \
const nsStyle##name_ * cachedData = \
static_cast<nsStyle##name_*>( \
mCachedInheritedData.mStyleStructs[eStyleStruct_##name_]); \
if (cachedData) /* Have it cached already, yay */ \
return cachedData; \
if (!aComputeData) { \
/* We always cache inherited structs on the context when we */ \
/* compute them. */ \
return nullptr; \
} \
/* Have the rulenode deal */ \
AUTO_CHECK_DEPENDENCY(eStyleStruct_##name_); \
const nsStyle##name_ * newData; \
if (mSource.IsGeckoRuleNode()) { \
newData = mSource.AsGeckoRuleNode()-> \
GetStyle##name_<aComputeData>(this, mBits); \
} else { \
/** \
* Reach the parent to grab the inherited style struct if \
* we're a text node. \
* \
* This causes the parent element's style context to cache any \
* inherited structs we request for a text node, which means we \
* don't have to compute change hints for the text node, as \
* handling the change on the parent element is sufficient. \
* \
* Note that adding the inherit bit is ok, because the struct \
* pointer returned by the parent and the child is owned by \
* Servo. This is fine if the pointers are the same (as it \
* should, read below), because both style context sources will \
* hold it. \
* \
* In the case of a mishandled frame, we could end up with the \
* pointer to and old parent style, but that's fine too, since \
* the parent style context will remain alive until we reframe, \
* in which case we'll discard both style contexts. Also, we \
* hold a strong reference to the parent style context, which \
* makes it a non-issue. \
* \
* Also, note that the assertion below should be true, except \
* for those frames we still don't handle correctly, like \
* anonymous table wrappers, in which case the pointers will \
* differ. \
* \
* That means we're not going to restyle correctly text frames \
* of anonymous table wrappers, for example. It's kind of \
* embarrassing, but I think it's not worth it to add more \
* logic here unconditionally, given that's going to be fixed. \
* \
* TODO(emilio): Convert to a strong assertion once we support \
* all kinds of random frames. In fact, this can be a great \
* assertion to debug them. \
*/ \
if (mPseudoTag == nsCSSAnonBoxes::mozText) { \
MOZ_ASSERT(mParent); \
newData = mParent->DoGetStyle##name_<true>(); \
NS_WARNING_ASSERTION( \
newData == Servo_GetStyle##name_(mSource.AsServoComputedValues()), \
"bad newData"); \
} else { \
newData = \
Servo_GetStyle##name_(mSource.AsServoComputedValues()); \
} \
/* perform any remaining main thread work on the struct */ \
const_cast<nsStyle##name_*>(newData)->FinishStyle(PresContext());\
/* the Servo-backed StyleContextSource owns the struct */ \
AddStyleBit(NS_STYLE_INHERIT_BIT(name_)); \
} \
/* always cache inherited data on the style context; the rule */ \
/* node set the bit in mBits for us if needed. */ \
mCachedInheritedData.mStyleStructs[eStyleStruct_##name_] = \
const_cast<nsStyle##name_ *>(newData); \
return newData; \
}
#define STYLE_STRUCT_RESET(name_, checkdata_cb_) \
template<bool aComputeData> \
const nsStyle##name_ * DoGetStyle##name_() { \
if (mCachedResetData) { \
const nsStyle##name_ * cachedData = \
static_cast<nsStyle##name_*>( \
mCachedResetData->mStyleStructs[eStyleStruct_##name_]); \
if (cachedData) /* Have it cached already, yay */ \
return cachedData; \
} \
/* Have the rulenode deal */ \
AUTO_CHECK_DEPENDENCY(eStyleStruct_##name_); \
const nsStyle##name_ * newData; \
if (mSource.IsGeckoRuleNode()) { \
newData = mSource.AsGeckoRuleNode()-> \
GetStyle##name_<aComputeData>(this); \
} else { \
newData = \
Servo_GetStyle##name_(mSource.AsServoComputedValues()); \
/* perform any remaining main thread work on the struct */ \
const_cast<nsStyle##name_*>(newData)->FinishStyle(PresContext());\
/* The Servo-backed StyleContextSource owns the struct. \
* \
* XXXbholley: Unconditionally caching reset structs here \
* defeats the memory optimization where we lazily allocate \
* mCachedResetData, so that we can avoid performing an FFI \
* call each time we want to get the style structs. We should \
* measure the tradeoffs at some point. If the FFI overhead is \
* low and the memory win significant, we should consider \
* _always_ grabbing the struct over FFI, and potentially \
* giving mCachedInheritedData the same treatment. \
* \
* Note that there is a similar comment in StyleData(). \
*/ \
AddStyleBit(NS_STYLE_INHERIT_BIT(name_)); \
SetStyle(eStyleStruct_##name_, \
const_cast<nsStyle##name_*>(newData)); \
} \
return newData; \
}
#include "nsStyleStructList.h"
#undef STYLE_STRUCT_RESET
#undef STYLE_STRUCT_INHERITED
// Helper for ClearCachedInheritedStyleDataOnDescendants.
void DoClearCachedInheritedStyleDataOnDescendants(uint32_t aStructs);
#ifdef DEBUG
void AssertStructsNotUsedElsewhere(nsStyleContext* aDestroyingContext,
int32_t aLevels) const;
#endif
#ifdef RESTYLE_LOGGING
void LogStyleContextTree(bool aFirst, uint32_t aStructs);
// This only gets called under call trees where we've already checked
// that PresContext()->RestyleManager()->ShouldLogRestyle() returned true.
// It exists here just to satisfy LOG_RESTYLE's expectations.
bool ShouldLogRestyle() { return true; }
#endif
RefPtr<nsStyleContext> mParent;
// Children are kept in two circularly-linked lists. The list anchor
// is not part of the list (null for empty), and we point to the first
// child.
// mEmptyChild for children whose rule node is the root rule node, and
// mChild for other children. The order of children is not
// meaningful.
nsStyleContext* mChild;
nsStyleContext* mEmptyChild;
nsStyleContext* mPrevSibling;
nsStyleContext* mNextSibling;
// Style to be used instead for the R, G, and B components of color,
// background-color, and border-*-color if the nearest ancestor link
// element is visited (see RelevantLinkVisited()).
RefPtr<nsStyleContext> mStyleIfVisited;
// If this style context is for a pseudo-element or anonymous box,
// the relevant atom.
nsCOMPtr<nsIAtom> mPseudoTag;
// The source for our style data, either a Gecko nsRuleNode or a Servo
// ComputedValues struct. This never changes after construction, except
// when it's released and nulled out during teardown.
const mozilla::OwningStyleContextSource mSource;
#ifdef MOZ_STYLO
// In Gecko, we can get this off the rule node. We make this conditional
// on stylo builds to avoid the memory bloat on release.
nsPresContext* mPresContext;
#endif
// mCachedInheritedData and mCachedResetData point to both structs that
// are owned by this style context and structs that are owned by one of
// this style context's ancestors (which are indirectly owned since this
// style context owns a reference to its parent). If the bit in |mBits|
// is set for a struct, that means that the pointer for that struct is
// owned by an ancestor or by the rule node rather than by this style context.
// Since style contexts typically have some inherited data but only sometimes
// have reset data, we always allocate the mCachedInheritedData, but only
// sometimes allocate the mCachedResetData.
nsResetStyleData* mCachedResetData; // Cached reset style data.
nsInheritedStyleData mCachedInheritedData; // Cached inherited style data
// mBits stores a number of things:
// - It records (using the style struct bits) which structs are
// inherited from the parent context or owned by the rule node (i.e.,
// not owned by the style context).
// - It also stores the additional bits listed at the top of
// nsStyleStruct.h.
uint64_t mBits;
uint32_t mRefCnt;
#ifdef DEBUG
uint32_t mFrameRefCnt; // number of frames that use this
// as their style context
nsStyleStructID mComputingStruct;
static bool DependencyAllowed(nsStyleStructID aOuterSID,
nsStyleStructID aInnerSID)
{
return !!(sDependencyTable[aOuterSID] &
nsCachedStyleData::GetBitForSID(aInnerSID));
}
static const uint32_t sDependencyTable[];
#endif
};
already_AddRefed<nsStyleContext>
NS_NewStyleContext(nsStyleContext* aParentContext,
nsIAtom* aPseudoTag,
mozilla::CSSPseudoElementType aPseudoType,
nsRuleNode* aRuleNode,
bool aSkipParentDisplayBasedStyleFixup);
already_AddRefed<nsStyleContext>
NS_NewStyleContext(nsStyleContext* aParentContext,
nsPresContext* aPresContext,
nsIAtom* aPseudoTag,
mozilla::CSSPseudoElementType aPseudoType,
already_AddRefed<ServoComputedValues> aComputedValues,
bool aSkipParentDisplayBasedStyleFixup);
#endif
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