1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/layout/style/nsIStyleRule.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,81 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +/*
1.10 + * internal abstract interface for objects providing immutable style
1.11 + * information
1.12 + */
1.13 +
1.14 +#ifndef nsIStyleRule_h___
1.15 +#define nsIStyleRule_h___
1.16 +
1.17 +#include <stdio.h>
1.18 +
1.19 +#include "nsISupports.h"
1.20 +
1.21 +struct nsRuleData;
1.22 +
1.23 +// IID for the nsIStyleRule interface {f75f3f70-435d-43a6-a01b-65970489ca26}
1.24 +#define NS_ISTYLE_RULE_IID \
1.25 +{ 0xf75f3f70, 0x435d, 0x43a6, \
1.26 + { 0xa0, 0x1b, 0x65, 0x97, 0x04, 0x89, 0xca, 0x26 } }
1.27 +
1.28 +/**
1.29 + * An object implementing |nsIStyleRule| (henceforth, a rule) represents
1.30 + * immutable stylistic information that either applies or does not apply
1.31 + * to a given element. It belongs to an object or group of objects that
1.32 + * implement |nsIStyleSheet| and |nsIStyleRuleProcessor| (henceforth, a
1.33 + * sheet).
1.34 + *
1.35 + * A rule becomes relevant to the computation of style data when
1.36 + * |nsIStyleRuleProcessor::RulesMatching| creates a rule node that
1.37 + * points to the rule. (A rule node, |nsRuleNode|, is a node in the
1.38 + * rule tree, which is a lexicographic tree indexed by rules. The path
1.39 + * from the root of the rule tree to the |nsRuleNode| for a given
1.40 + * |nsStyleContext| contains exactly the rules that match the element
1.41 + * that the style context is for, in priority (weight, origin,
1.42 + * specificity) order.)
1.43 + *
1.44 + * The computation of style data uses the rule tree, which calls
1.45 + * |nsIStyleRule::MapRuleInfoInto| below.
1.46 + *
1.47 + * It is worth emphasizing that the data represented by a rule
1.48 + * implementation are immutable. When the data need to be changed, a
1.49 + * new rule object must be created. Failing to do this will lead to
1.50 + * bugs in the handling of dynamic style changes, since the rule tree
1.51 + * caches the results of |MapRuleInfoInto|.
1.52 + *
1.53 + * |nsIStyleRule| objects are owned by |nsRuleNode| objects (in addition
1.54 + * to typically being owned by their sheet), which are in turn garbage
1.55 + * collected (with the garbage collection roots being style contexts).
1.56 + */
1.57 +
1.58 +
1.59 +class nsIStyleRule : public nsISupports {
1.60 +public:
1.61 + NS_DECLARE_STATIC_IID_ACCESSOR(NS_ISTYLE_RULE_IID)
1.62 +
1.63 + /**
1.64 + * |nsIStyleRule::MapRuleInfoInto| is a request to copy all stylistic
1.65 + * data represented by the rule that:
1.66 + * + are relevant for any structs in |aRuleData->mSIDs| (style
1.67 + * struct ID bits)
1.68 + * + are not already filled into the data struct
1.69 + * into the appropriate data struct in |aRuleData|. It is important
1.70 + * that only empty data are filled in, since the rule tree is walked
1.71 + * from highest priority rule to least, so that the walk can stop if
1.72 + * all needed data are found. Thus overwriting non-empty data will
1.73 + * break CSS cascading rules.
1.74 + */
1.75 + virtual void MapRuleInfoInto(nsRuleData* aRuleData)=0;
1.76 +
1.77 +#ifdef DEBUG
1.78 + virtual void List(FILE* out = stdout, int32_t aIndent = 0) const = 0;
1.79 +#endif
1.80 +};
1.81 +
1.82 +NS_DEFINE_STATIC_IID_ACCESSOR(nsIStyleRule, NS_ISTYLE_RULE_IID)
1.83 +
1.84 +#endif /* nsIStyleRule_h___ */
