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e5eb83ac5a
This patch enables sharing of an nsAttrValue's MiscContainer between nodes for style rules. MiscContainers of type eCSSStyleRule are now refcounted (with some clever struct packing to ensure that the amount of memory allocated for MiscContainer remains unchanged on 32 and 64 bit). This infrastructure can be used to share most MiscContainer types in the future if we find advantages to sharing other types than just eCSSStyleRuley. A cache mapping strings to MiscContainers has been added to nsHTMLCSSStyleSheet. MiscContainers can be shared between nsAttrValues when one nsAttrValue is SetTo another nsAttrValue or when there is a cache hit in this cache. This patch also adds the ability to tell a style rule that it belongs to an nsHTMLCSSStyleSheet, with appropriate accessor functions to separate that from the existing case of belonging to an nsCSSStyleSheet. The primary use case is to reduce memory use for pages that have lots of inline style attributes with the same value. This can happen easily with large pages that are automatically generated. An (admittedly pathological) testcase in Bug 686975 sees over 250 MB of memory savings with this change. Reusing the same MiscContainer for multiple nodes saves the overhead of maintaining separate copies of the string containing the serialized value of the style attribute and of creating separate style rules for each node. Eliminating duplicate style rules enables further savings in layout through style context sharing. The testcase sees the amount of memory used by style contexts go from over 250 MB to 10 KB. Because the cache is based on the text value of the style attribute, it will not handle attributes that have different text values but are parsed into identical style rules. We also do not attempt to share MiscContainers when the node's base URI differs from the document URI. The effect of these limitations is expected to be low.
135 lines
3.7 KiB
C++
135 lines
3.7 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* base class for all rule types in a CSS style sheet */
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#ifndef mozilla_css_Rule_h___
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#define mozilla_css_Rule_h___
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#include "nsIStyleRule.h"
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#include "nsIDOMCSSRule.h"
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#include "nsCSSStyleSheet.h"
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class nsIStyleSheet;
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class nsIDocument;
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struct nsRuleData;
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template<class T> struct already_AddRefed;
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class nsHTMLCSSStyleSheet;
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namespace mozilla {
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namespace css {
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class GroupRule;
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#define DECL_STYLE_RULE_INHERIT_NO_DOMRULE \
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virtual void MapRuleInfoInto(nsRuleData* aRuleData);
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#define DECL_STYLE_RULE_INHERIT \
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DECL_STYLE_RULE_INHERIT_NO_DOMRULE \
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virtual nsIDOMCSSRule* GetDOMRule();
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class Rule : public nsIStyleRule {
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protected:
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Rule()
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: mSheet(0),
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mParentRule(nullptr)
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{
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}
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Rule(const Rule& aCopy)
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: mSheet(aCopy.mSheet),
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mParentRule(aCopy.mParentRule)
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{
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}
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virtual ~Rule() {}
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public:
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// for implementing nsISupports
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NS_IMETHOD_(nsrefcnt) AddRef();
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NS_IMETHOD_(nsrefcnt) Release();
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protected:
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nsAutoRefCnt mRefCnt;
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NS_DECL_OWNINGTHREAD
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public:
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// The constants in this list must maintain the following invariants:
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// If a rule of type N must appear before a rule of type M in stylesheets
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// then N < M
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// Note that nsCSSStyleSheet::RebuildChildList assumes that no other kinds of
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// rules can come between two rules of type IMPORT_RULE.
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enum {
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UNKNOWN_RULE = 0,
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CHARSET_RULE,
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IMPORT_RULE,
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NAMESPACE_RULE,
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STYLE_RULE,
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MEDIA_RULE,
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FONT_FACE_RULE,
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PAGE_RULE,
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KEYFRAME_RULE,
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KEYFRAMES_RULE,
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DOCUMENT_RULE,
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SUPPORTS_RULE
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};
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virtual int32_t GetType() const = 0;
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nsCSSStyleSheet* GetStyleSheet() const;
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nsHTMLCSSStyleSheet* GetHTMLCSSStyleSheet() const;
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// Return the document the rule lives in, if any
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nsIDocument* GetDocument() const
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{
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nsCSSStyleSheet* sheet = GetStyleSheet();
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return sheet ? sheet->GetDocument() : nullptr;
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}
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virtual void SetStyleSheet(nsCSSStyleSheet* aSheet);
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// This does not need to be virtual, because GroupRule and MediaRule are not
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// used for inline style.
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void SetHTMLCSSStyleSheet(nsHTMLCSSStyleSheet* aSheet);
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void SetParentRule(GroupRule* aRule) {
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// We don't reference count this up reference. The group rule
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// will tell us when it's going away or when we're detached from
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// it.
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mParentRule = aRule;
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}
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/**
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* Clones |this|. Never returns NULL.
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*/
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virtual already_AddRefed<Rule> Clone() const = 0;
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// Note that this returns null for inline style rules since they aren't
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// supposed to have a DOM rule representation (and our code wouldn't work).
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virtual nsIDOMCSSRule* GetDOMRule() = 0;
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// to implement methods on nsIDOMCSSRule
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nsresult GetParentRule(nsIDOMCSSRule** aParentRule);
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nsresult GetParentStyleSheet(nsIDOMCSSStyleSheet** aSheet);
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// This is pure virtual because all of Rule's data members are non-owning and
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// thus measured elsewhere.
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virtual NS_MUST_OVERRIDE size_t
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SizeOfIncludingThis(nsMallocSizeOfFun aMallocSizeOf) const = 0;
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// This is used to measure nsCOMArray<Rule>s.
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static size_t SizeOfCOMArrayElementIncludingThis(css::Rule* aElement,
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nsMallocSizeOfFun aMallocSizeOf,
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void* aData);
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protected:
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// This is either an nsCSSStyleSheet* or a nsHTMLStyleSheet*. The former
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// if the low bit is 0, the latter if the low bit is 1.
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uintptr_t mSheet;
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GroupRule* mParentRule;
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};
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} // namespace css
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} // namespace mozilla
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#endif /* mozilla_css_Rule_h___ */
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