97 lines
3.5 KiB
C++
97 lines
3.5 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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/*
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* internal abstract interface for objects providing immutable style
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* information
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*/
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#ifndef nsIStyleRule_h___
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#define nsIStyleRule_h___
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#include <stdio.h>
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#include "nsCSSPropertyID.h"
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#include "nsISupports.h"
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class nsCSSValue;
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struct nsRuleData;
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// IID for the nsIStyleRule interface {f75f3f70-435d-43a6-a01b-65970489ca26}
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#define NS_ISTYLE_RULE_IID \
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{ 0xf75f3f70, 0x435d, 0x43a6, \
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{ 0xa0, 0x1b, 0x65, 0x97, 0x04, 0x89, 0xca, 0x26 } }
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/**
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* An object implementing |nsIStyleRule| (henceforth, a rule) represents
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* immutable stylistic information that either applies or does not apply
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* to a given element. It belongs to an object or group of objects that
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* implement |nsIStyleSheet| and |nsIStyleRuleProcessor| (henceforth, a
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* sheet).
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*
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* A rule becomes relevant to the computation of style data when
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* |nsIStyleRuleProcessor::RulesMatching| creates a rule node that
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* points to the rule. (A rule node, |nsRuleNode|, is a node in the
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* rule tree, which is a lexicographic tree indexed by rules. The path
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* from the root of the rule tree to the |nsRuleNode| for a given
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* |nsStyleContext| contains exactly the rules that match the element
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* that the style context is for, in priority (weight, origin,
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* specificity) order.)
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*
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* The computation of style data uses the rule tree, which calls
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* |nsIStyleRule::MapRuleInfoInto| below.
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*
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* It is worth emphasizing that the data represented by a rule
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* implementation are immutable. When the data need to be changed, a
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* new rule object must be created. Failing to do this will lead to
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* bugs in the handling of dynamic style changes, since the rule tree
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* caches the results of |MapRuleInfoInto|.
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*
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* |nsIStyleRule| objects are owned by |nsRuleNode| objects (in addition
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* to typically being owned by their sheet), which are in turn garbage
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* collected (with the garbage collection roots being style contexts).
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*/
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class nsIStyleRule : public nsISupports {
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public:
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NS_DECLARE_STATIC_IID_ACCESSOR(NS_ISTYLE_RULE_IID)
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/**
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* |nsIStyleRule::MapRuleInfoInto| is a request to copy all stylistic
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* data represented by the rule that:
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* + are relevant for any structs in |aRuleData->mSIDs| (style
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* struct ID bits)
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* + are not already filled into the data struct
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* into the appropriate data struct in |aRuleData|. It is important
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* that only empty data are filled in, since the rule tree is walked
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* from highest priority rule to least, so that the walk can stop if
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* all needed data are found. Thus overwriting non-empty data will
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* break CSS cascading rules.
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*/
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virtual void MapRuleInfoInto(nsRuleData* aRuleData)=0;
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/**
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* Returns whether this style rule has any style data for inherited
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* properties.
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*/
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virtual bool MightMapInheritedStyleData() = 0;
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/**
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* Gets and sets given aProperty's value to aValue.
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* Returns true, if aValue is filled in this rule.
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*/
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virtual bool GetDiscretelyAnimatedCSSValue(nsCSSPropertyID aProperty,
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nsCSSValue* aValue) = 0;
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#ifdef DEBUG
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virtual void List(FILE* out = stdout, int32_t aIndent = 0) const = 0;
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#endif
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};
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NS_DEFINE_STATIC_IID_ACCESSOR(nsIStyleRule, NS_ISTYLE_RULE_IID)
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#endif /* nsIStyleRule_h___ */
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