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tenfourfox/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/RestyleLogging.h"
#include "mozilla/Assertions.h"
#include "nsRuleNode.h"
#include "nsCSSPseudoElements.h"
class nsIAtom;
class nsPresContext;
/**
* 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,
* nsFrameManager::ReResolveStyleContext 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)
* Style contexts participate in the mark phase of rule node garbage
* collection.
*/
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,
nsCSSPseudoElements::Type aPseudoType,
nsRuleNode* aRuleNode,
bool aSkipParentDisplayBasedStyleFixup);
void* operator new(size_t sz, nsPresContext* aPresContext) CPP_THROW_NEW;
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 { return mRuleNode->PresContext(); }
nsStyleContext* GetParent() const { return mParent; }
nsIAtom* GetPseudo() const { return mPseudoTag; }
nsCSSPseudoElements::Type GetPseudoType() const {
return static_cast<nsCSSPseudoElements::Type>(mBits >>
NS_STYLE_CONTEXT_TYPE_SHIFT);
}
// 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
// * RuleNode() matches aRules
// * !GetStyleIfVisited() == !aRulesIfVisited, and, if they're
// non-null, GetStyleIfVisited()->RuleNode() == aRulesIfVisited
// * RelevantLinkVisited() == aRelevantLinkVisited
already_AddRefed<nsStyleContext>
FindChildWithRules(const nsIAtom* aPseudoTag, nsRuleNode* aRules,
nsRuleNode* aRulesIfVisited,
bool aRelevantLinkVisited);
// Does this style context or any of its ancestors have text
// decoration lines?
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); }
// 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 GetPseudo.
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() { return mRuleNode; }
void AddStyleBit(const uint64_t& aBit) { mBits |= aBit; }
/*
* Mark this style context's rule node (and its ancestors) to prevent
* it from being garbage collected.
*/
void Mark();
/*
* 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 aOther. (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* aOther,
nsChangeHint aParentHintsNotHandledForDescendants,
uint32_t* aEqualStructs,
uint32_t* aSamePointerStructs);
/**
* Get a color that depends on link-visitedness using this and
* this->GetStyleIfVisited().
*
* aProperty must be a color-valued property that StyleAnimationValue
* knows how to extract. It must also be a property that we know to
* do change handling for in nsStyleContext::CalcDifference.
*
* Note that if aProperty is eCSSProperty_border_*_color, this
* function handles -moz-use-text-color.
*/
nscolor GetVisitedDependentColor(nsCSSProperty aProperty);
/**
* 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;
}
private:
// Private destructor, to discourage deletion outside of Release():
~nsStyleContext();
void AddChild(nsStyleContext* aChild);
void RemoveChild(nsStyleContext* aChild);
void* GetUniqueStyleData(const nsStyleStructID& aSID);
void* CreateEmptyStyleData(const nsStyleStructID& aSID);
void ApplyStyleFixups(bool aSkipParentDisplayBasedStyleFixup);
#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 = \
mRuleNode->GetStyle##name_<aComputeData>(this, mBits); \
/* 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_); \
return mRuleNode->GetStyle##name_<aComputeData>(this); \
}
#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
nsStyleContext* mParent; // STRONG
// 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 rule node is the node in the lexicographic tree of rule nodes
// (the "rule tree") that indicates which style rules are used to
// compute the style data, and in what cascading order. The least
// specific rule matched is the one whose rule node is a child of the
// root of the rule tree, and the most specific rule matched is the
// |mRule| member of |mRuleNode|.
nsRuleNode* const mRuleNode;
// 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 mRuleNode 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 mRuleNode (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,
nsCSSPseudoElements::Type aPseudoType,
nsRuleNode* aRuleNode,
bool aSkipParentDisplayBasedStyleFixup);
#endif
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