The Tor Browser: layout/style/nsStyleContext.h@7e26c7da4463 (annotated)

layout/style/nsStyleContext.h@7e26c7da4463 (annotated)

layout/style/nsStyleContext.h

Wed, 31 Dec 2014 06:55:50 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:55:50 +0100
changeset 2: 7e26c7da4463
permissions: -rw-r--r--

Added tag UPSTREAM_283F7C6 for changeset ca08bd8f51b2

 /* -*- 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
 {
 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 aSkipFlexItemStyleFixup
    *                 If set, this flag indicates that we should skip
    *                 the chunk of ApplyStyleFixups() that modifies flex
    *                 items' display values.
    */
   nsStyleContext(nsStyleContext* aParent, nsIAtom* aPseudoTag,
                  nsCSSPseudoElements::Type aPseudoType,
                  nsRuleNode* aRuleNode,
                  bool aSkipFlexItemStyleFixup);
   ~nsStyleContext();
   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;
   }
   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); }
   // 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<nsStyleContext> 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");
     }
   }
   // 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
   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.
    */
   nsChangeHint CalcStyleDifference(nsStyleContext* aOther,
                                    nsChangeHint aParentHintsNotHandledForDescendants);
   /**
    * Get a color that depends on link-visitedness using this and
    * this->GetStyleIfVisited().
    *
    * aProperty must be a color-valued property that nsStyleAnimation
    * 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);
   /**
    * Allocate a chunk of memory that is scoped to the lifetime of this
    * style context, i.e., memory that will automatically be freed when
    * this style context is destroyed.  This is intended for allocations
    * that are stored on this style context or its style structs.  (Use
    * on style structs is fine since any style context to which this
    * context's style structs are shared will be a descendant of this
    * style context and thus keep it alive.)
    *
    * This currently allocates the memory out of the pres shell arena.
    *
    * It would be relatively straightforward to write a Free method
    * for the underlying implementation, but we don't need it (or the
    * overhead of making a doubly-linked list or other structure to
    * support it).
    *
    * WARNING: Memory allocated using this method cannot be stored in the
    * rule tree, since rule nodes may outlive the style context.
    */
   void* Alloc(size_t aSize);
   /**
    * Start the background image loads for this style context.
    */
   void StartBackgroundImageLoads() {
     // Just get our background struct; that should do the trick
     StyleBackground();
   }
 #ifdef DEBUG
   void List(FILE* out, int32_t aIndent);
   static void AssertStyleStructMaxDifferenceValid();
 #endif
 protected:
   void AddChild(nsStyleContext* aChild);
   void RemoveChild(nsStyleContext* aChild);
   void ApplyStyleFixups(bool aSkipFlexItemStyleFixup);
   void FreeAllocations(nsPresContext* aPresContext);
   // 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<nsStyle##name_*>(                                   \
           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<nsStyle##name_*>(                                 \
             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
   nsStyleContext* const 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<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;
   // Private to nsStyleContext::Alloc and FreeAllocations.
   struct AllocationHeader {
     AllocationHeader* mNext;
     size_t mSize;
     void* mStorageStart; // ensure the storage is at least pointer-aligned
   };
   AllocationHeader*       mAllocations;
   // 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<nsStyleContext>
 NS_NewStyleContext(nsStyleContext* aParentContext,
                    nsIAtom* aPseudoTag,
                    nsCSSPseudoElements::Type aPseudoType,
                    nsRuleNode* aRuleNode,
                    bool aSkipFlexItemStyleFixup);
 #endif

The Tor Browser / annotate

layout/style/nsStyleContext.h@7e26c7da4463 (annotated)

layout/style/nsStyleContext.h