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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/. */
/*
* internal abstract interface for objects providing immutable style
* information
*/
#ifndef nsIStyleRule_h___
#define nsIStyleRule_h___
#include <stdio.h>
#include "nsCSSPropertyID.h"
#include "nsISupports.h"
class nsCSSValue;
struct nsRuleData;
// IID for the nsIStyleRule interface {f75f3f70-435d-43a6-a01b-65970489ca26}
#define NS_ISTYLE_RULE_IID \
{ 0xf75f3f70, 0x435d, 0x43a6, \
{ 0xa0, 0x1b, 0x65, 0x97, 0x04, 0x89, 0xca, 0x26 } }
/**
* 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 any structs in |aRuleData->mSIDs| (style
* struct ID bits)
* + 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.
*/
virtual void MapRuleInfoInto(nsRuleData* aRuleData)=0;
/**
* Returns whether this style rule has any style data for inherited
* properties.
*/
virtual bool MightMapInheritedStyleData() = 0;
/**
* Gets and sets given aProperty's value to aValue.
* Returns true, if aValue is filled in this rule.
*/
virtual bool GetDiscretelyAnimatedCSSValue(nsCSSPropertyID aProperty,
nsCSSValue* aValue) = 0;
#ifdef DEBUG
virtual void List(FILE* out = stdout, int32_t aIndent = 0) const = 0;
#endif
};
NS_DEFINE_STATIC_IID_ACCESSOR(nsIStyleRule, NS_ISTYLE_RULE_IID)
#endif /* nsIStyleRule_h___ */
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