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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 "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