/* -*- 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 "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 MOZ_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(); 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; } 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(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 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); } // 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); } // 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 aStyleIfVisited) { NS_ABORT_IF_FALSE(!IsStyleIfVisited(), "this context is not visited data"); NS_ASSERTION(!mStyleIfVisited, "should only be set once"); mStyleIfVisited = aStyleIfVisited; NS_ABORT_IF_FALSE(mStyleIfVisited->IsStyleIfVisited(), "other context is visited data"); NS_ABORT_IF_FALSE(!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 this style context, or any of its descendants, have any style values // that were computed based on this style context's grandparent style context // or any of the grandparent's ancestors? bool UsesGrandancestorStyle() const { return !!(mBits & NS_STYLE_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); } // Does this style context have any children that return true for // UsesGrandancestorStyle()? bool HasChildThatUsesGrandancestorStyle() const; // Tell this style context to cache aStruct as the struct for aSID void SetStyle(nsStyleStructID aSID, void* aStruct); // Setters for inherit structs only, since rulenode only sets those eagerly. #define STYLE_STRUCT_INHERITED(name_, checkdata_cb_) \ void SetStyle##name_ (nsStyle##name_ * aStruct) { \ void *& slot = \ mCachedInheritedData.mStyleStructs[eStyleStruct_##name_]; \ NS_ASSERTION(!slot || \ (mBits & \ nsCachedStyleData::GetBitForSID(eStyleStruct_##name_)), \ "Going to leak styledata"); \ slot = aStruct; \ } #define STYLE_STRUCT_RESET(name_, checkdata_cb_) /* nothing */ #include "nsStyleStructList.h" #undef STYLE_STRUCT_RESET #undef STYLE_STRUCT_INHERITED /** * Returns whether this style context and aOther both have the same * cached style struct pointer for a given style struct. */ bool HasSameCachedStyleData(nsStyleContext* aOther, nsStyleStructID aSID); /** * Returns whether this style context has cached, inherited style data for a * given style struct. */ bool HasCachedInheritedStyleData(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 nsIStyleContext. 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 GetStyle* 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 void* GetUniqueStyleData(const nsStyleStructID& aSID); /** * 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); /** * 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); #ifdef DEBUG void List(FILE* out, int32_t aIndent); static void AssertStyleStructMaxDifferenceValid(); #endif private: // Private destructor, to discourage deletion outside of Release(): ~nsStyleContext(); void AddChild(nsStyleContext* aChild); void RemoveChild(nsStyleContext* aChild); void ApplyStyleFixups(bool aSkipParentDisplayBasedStyleFixup); // Helper function for HasChildThatUsesGrandancestorStyle. static bool ListContainsStyleContextThatUsesGrandancestorStyle( const nsStyleContext* aHead); // Helper function that GetStyleData and GetUniqueStyleData use. Only // returns the structs we cache ourselves; never consults the ruletree. inline const void* GetCachedStyleData(nsStyleStructID aSID); // Helper functions for GetStyle* and PeekStyle* #define STYLE_STRUCT_INHERITED(name_, checkdata_cb_) \ const nsStyle##name_ * DoGetStyle##name_(bool aComputeData) { \ const nsStyle##name_ * cachedData = \ static_cast( \ mCachedInheritedData.mStyleStructs[eStyleStruct_##name_]); \ if (cachedData) /* Have it cached already, yay */ \ return cachedData; \ /* Have the rulenode deal */ \ return mRuleNode->GetStyle##name_(this, aComputeData); \ } #define STYLE_STRUCT_RESET(name_, checkdata_cb_) \ const nsStyle##name_ * DoGetStyle##name_(bool aComputeData) { \ const nsStyle##name_ * cachedData = mCachedResetData \ ? static_cast( \ mCachedResetData->mStyleStructs[eStyleStruct_##name_]) \ : nullptr; \ if (cachedData) /* Have it cached already, yay */ \ return cachedData; \ /* Have the rulenode deal */ \ return mRuleNode->GetStyle##name_(this, aComputeData); \ } #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 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()). nsRefPtr mStyleIfVisited; // If this style context is for a pseudo-element or anonymous box, // the relevant atom. nsCOMPtr 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 uint64_t mBits; // Which structs are inherited from the // parent context or owned by mRuleNode. uint32_t mRefCnt; }; already_AddRefed NS_NewStyleContext(nsStyleContext* aParentContext, nsIAtom* aPseudoTag, nsCSSPseudoElements::Type aPseudoType, nsRuleNode* aRuleNode, bool aSkipParentDisplayBasedStyleFixup); #endif