layout/style/nsIStyleRule.h@925c144e1f1f (annotated)
layout/style/nsIStyleRule.h
Fri, 16 Jan 2015 18:13:44 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Fri, 16 Jan 2015 18:13:44 +0100
- branch
- TOR_BUG_9701
- changeset 14
- 925c144e1f1f
- permissions
- -rw-r--r--
Integrate suggestion from review to improve consistency with existing code.
| michael@0 | 1 | /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ |
| michael@0 | 2 | /* This Source Code Form is subject to the terms of the Mozilla Public |
| michael@0 | 3 | * License, v. 2.0. If a copy of the MPL was not distributed with this |
| michael@0 | 4 | * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
| michael@0 | 5 | |
| michael@0 | 6 | /* |
| michael@0 | 7 | * internal abstract interface for objects providing immutable style |
| michael@0 | 8 | * information |
| michael@0 | 9 | */ |
| michael@0 | 10 | |
| michael@0 | 11 | #ifndef nsIStyleRule_h___ |
| michael@0 | 12 | #define nsIStyleRule_h___ |
| michael@0 | 13 | |
| michael@0 | 14 | #include <stdio.h> |
| michael@0 | 15 | |
| michael@0 | 16 | #include "nsISupports.h" |
| michael@0 | 17 | |
| michael@0 | 18 | struct nsRuleData; |
| michael@0 | 19 | |
| michael@0 | 20 | // IID for the nsIStyleRule interface {f75f3f70-435d-43a6-a01b-65970489ca26} |
| michael@0 | 21 | #define NS_ISTYLE_RULE_IID \ |
| michael@0 | 22 | { 0xf75f3f70, 0x435d, 0x43a6, \ |
| michael@0 | 23 | { 0xa0, 0x1b, 0x65, 0x97, 0x04, 0x89, 0xca, 0x26 } } |
| michael@0 | 24 | |
| michael@0 | 25 | /** |
| michael@0 | 26 | * An object implementing |nsIStyleRule| (henceforth, a rule) represents |
| michael@0 | 27 | * immutable stylistic information that either applies or does not apply |
| michael@0 | 28 | * to a given element. It belongs to an object or group of objects that |
| michael@0 | 29 | * implement |nsIStyleSheet| and |nsIStyleRuleProcessor| (henceforth, a |
| michael@0 | 30 | * sheet). |
| michael@0 | 31 | * |
| michael@0 | 32 | * A rule becomes relevant to the computation of style data when |
| michael@0 | 33 | * |nsIStyleRuleProcessor::RulesMatching| creates a rule node that |
| michael@0 | 34 | * points to the rule. (A rule node, |nsRuleNode|, is a node in the |
| michael@0 | 35 | * rule tree, which is a lexicographic tree indexed by rules. The path |
| michael@0 | 36 | * from the root of the rule tree to the |nsRuleNode| for a given |
| michael@0 | 37 | * |nsStyleContext| contains exactly the rules that match the element |
| michael@0 | 38 | * that the style context is for, in priority (weight, origin, |
| michael@0 | 39 | * specificity) order.) |
| michael@0 | 40 | * |
| michael@0 | 41 | * The computation of style data uses the rule tree, which calls |
| michael@0 | 42 | * |nsIStyleRule::MapRuleInfoInto| below. |
| michael@0 | 43 | * |
| michael@0 | 44 | * It is worth emphasizing that the data represented by a rule |
| michael@0 | 45 | * implementation are immutable. When the data need to be changed, a |
| michael@0 | 46 | * new rule object must be created. Failing to do this will lead to |
| michael@0 | 47 | * bugs in the handling of dynamic style changes, since the rule tree |
| michael@0 | 48 | * caches the results of |MapRuleInfoInto|. |
| michael@0 | 49 | * |
| michael@0 | 50 | * |nsIStyleRule| objects are owned by |nsRuleNode| objects (in addition |
| michael@0 | 51 | * to typically being owned by their sheet), which are in turn garbage |
| michael@0 | 52 | * collected (with the garbage collection roots being style contexts). |
| michael@0 | 53 | */ |
| michael@0 | 54 | |
| michael@0 | 55 | |
| michael@0 | 56 | class nsIStyleRule : public nsISupports { |
| michael@0 | 57 | public: |
| michael@0 | 58 | NS_DECLARE_STATIC_IID_ACCESSOR(NS_ISTYLE_RULE_IID) |
| michael@0 | 59 | |
| michael@0 | 60 | /** |
| michael@0 | 61 | * |nsIStyleRule::MapRuleInfoInto| is a request to copy all stylistic |
| michael@0 | 62 | * data represented by the rule that: |
| michael@0 | 63 | * + are relevant for any structs in |aRuleData->mSIDs| (style |
| michael@0 | 64 | * struct ID bits) |
| michael@0 | 65 | * + are not already filled into the data struct |
| michael@0 | 66 | * into the appropriate data struct in |aRuleData|. It is important |
| michael@0 | 67 | * that only empty data are filled in, since the rule tree is walked |
| michael@0 | 68 | * from highest priority rule to least, so that the walk can stop if |
| michael@0 | 69 | * all needed data are found. Thus overwriting non-empty data will |
| michael@0 | 70 | * break CSS cascading rules. |
| michael@0 | 71 | */ |
| michael@0 | 72 | virtual void MapRuleInfoInto(nsRuleData* aRuleData)=0; |
| michael@0 | 73 | |
| michael@0 | 74 | #ifdef DEBUG |
| michael@0 | 75 | virtual void List(FILE* out = stdout, int32_t aIndent = 0) const = 0; |
| michael@0 | 76 | #endif |
| michael@0 | 77 | }; |
| michael@0 | 78 | |
| michael@0 | 79 | NS_DEFINE_STATIC_IID_ACCESSOR(nsIStyleRule, NS_ISTYLE_RULE_IID) |
| michael@0 | 80 | |
| michael@0 | 81 | #endif /* nsIStyleRule_h___ */ |
