gecko-dev/layout/style/nsIStyleRule.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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* 1.1 (the "License"); you may not use this file except in compliance with
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*
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1998
* the Initial Developer. All Rights Reserved.
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* Contributor(s):
*
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/*
* internal abstract interface for objects providing immutable style
* information
*/
#ifndef nsIStyleRule_h___
#define nsIStyleRule_h___
#include <stdio.h>
#include "nsISupports.h"
class nsIStyleSheet;
class nsPresContext;
class nsIContent;
struct nsRuleData;
// IID for the nsIStyleRule interface {40ae5c90-ad6a-11d1-8031-006008159b5a}
#define NS_ISTYLE_RULE_IID \
{0x40ae5c90, 0xad6a, 0x11d1, {0x80, 0x31, 0x00, 0x60, 0x08, 0x15, 0x9b, 0x5a}}
/**
* An object implementing |nsIStyleRule| (henceforth, a rule) represents
* immutable stylistic information that either applies or does not apply
* to a given element. It belongs to an object or group of objects that
* implement |nsIStyleSheet| and |nsIStyleRuleProcessor| (henceforth, a
* sheet).
*
* A rule becomes relevant to the computation of style data when
* |nsIStyleRuleProcessor::RulesMatching| creates a rule node that
* points to the rule. (A rule node, |nsRuleNode|, is a node in the
* rule tree, which is a lexicographic tree indexed by rules. The path
* from the root of the rule tree to the |nsRuleNode| for a given
* |nsStyleContext| contains exactly the rules that match the element
* that the style context is for, in priority (weight, origin,
* specificity) order.)
*
* The computation of style data uses the rule tree, which calls
* |nsIStyleRule::MapRuleInfoInto| below.
*
* It is worth emphasizing that the data represented by a rule
* implementation are immutable. When the data need to be changed, a
* new rule object must be created. Failing to do this will lead to
* bugs in the handling of dynamic style changes, since the rule tree
* caches the results of |MapRuleInfoInto|.
*
* |nsIStyleRule| objects are owned by |nsRuleNode| objects (in addition
* to typically being owned by their sheet), which are in turn garbage
* collected (with the garbage collection roots being style contexts).
*/
class nsIStyleRule : public nsISupports {
public:
NS_DECLARE_STATIC_IID_ACCESSOR(NS_ISTYLE_RULE_IID)
/**
* |nsIStyleRule::MapRuleInfoInto| is a request to copy all stylistic
* data represented by the rule that:
* + are relevant for |aRuleData->mSID| (the style struct ID)
* + are not already filled into the data struct
* into the appropriate data struct in |aRuleData|. It is important
* that only empty data are filled in, since the rule tree is walked
* from highest priority rule to least, so that the walk can stop if
* all needed data are found. Thus overwriting non-empty data will
* break CSS cascading rules.
*/
NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData)=0;
#ifdef DEBUG
NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const = 0;
#endif
};
NS_DEFINE_STATIC_IID_ACCESSOR(nsIStyleRule, NS_ISTYLE_RULE_IID)
#endif /* nsIStyleRule_h___ */