/* -*- 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___ */