The Tor Browser: comparison layout/style/nsStyleContext.h

--1:000000000000
+:e563d1e80908
+/* -*- 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 / file comparison

comparison: layout/style/nsStyleContext.h

layout/style/nsStyleContext.h