third_party/WebKit/Source/core/svg/SVGElementProxy.h - Issue 2482353002: Revert of Tracking filter mutation via SVGElementProxy

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Issue 2482353002: Revert of Tracking filter mutation via SVGElementProxy (Closed)

Patch Set: Created 4 years, 1 month ago

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1 // Copyright 2016 The Chromium Authors. All rights reserved.

2 // Use of this source code is governed by a BSD-style license that can be

3 // found in the LICENSE file.

4

5 #ifndef SVGElementProxy_h

6 #define SVGElementProxy_h

7

8 #include "core/fetch/DocumentResource.h"

9 #include "platform/heap/Handle.h"

10 #include "wtf/text/AtomicString.h"

11 #include "wtf/text/WTFString.h"

12

13 namespace blink {

14

15 class Document;

16 class SVGElement;

17 class SVGResourceClient;

18 class TreeScope;

19

20 // A proxy to an SVGElement. Allows access to an element with a certain 'id',

21 // and provides its clients with notifications when the proxied element

22 // changes.

23 //

24 // SVGElements can be referenced using CSS, for example like:

25 //

26 // filter: url(#baz);

27 //

28 // or

29 //

30 // filter: url(foo.com/bar.svg#baz);

31 //

32 // SVGElementProxy provide a mechanism to persistently reference an SVGElement

33 // in such cases - regardless of if the proxied element reside in the same

34 // document (read: tree scope) or in an external (resource) document. Loading

35 // events related to external documents case needs be handled by the clients

36 // (SVGResourceClient's default implementation does this.)

37 //

38 // The proxy uses an 'id' (c.f getElementById) to determine which element to

39 // proxy. The id is looked up in the TreeScope provided by the client for a

40 // same-document reference and in the TreeScope of the Document for a external

41 // document reference.

42 //

43 // For same document references, the proxy will track changes that could affect

44 // the 'id' lookup, to handle elements being added, removed or having their

45 // 'id' mutated. (This does not apply for the external document case because

46 // it's assumed they will not mutate after load, due to scripts not being run

47 // etc.)

48 //

49 // SVGElementProxys are created by CSSURIValue, and have SVGResourceClients as

50 // a means to deliver change notifications. Clients that are interested in

51 // change notifications hence need to register a SVGResourceClient with the

52 // proxy. Most commonly this registration would take place when the

53 // ComputedStyle changes.

54 //

55 // Registration of a client does not establish a link to the proxied element

56 // right away. That is instead deferred until findElement(...) is called on the

57 // SVGElementProxy. At this point, the proxy will be registered with the

58 // element if the lookup is successful. (For external references lookups will

59 // not be registered, per the same assumption as mentioned above.)

60 //

61 // As content is mutated, clients will get notified via the proxied element

62 // which in turn will notify all registered proxies, which will notify all

63 // registered clients.

64 //

65 // <event> -> SVG...Element -> SVGElementProxy(0..N) -> SVGResourceClient(0..N)

66 //

67 class SVGElementProxy : public GarbageCollectedFinalized<SVGElementProxy> {

68 public:

69 // Create a proxy to an element in the same document. (See also

70 // SVGURLReferenceResolver and the definition of 'local url'.)

71 static SVGElementProxy* create(const AtomicString& id) {

72 return new SVGElementProxy(id);

73 }

74

75 // Create a proxy to an element in a different document (indicated by \|url\|.)

76 static SVGElementProxy* create(const String& url, const AtomicString& id) {

77 return new SVGElementProxy(url, id);

78 }

79 virtual ~SVGElementProxy();

80

81 void addClient(SVGResourceClient*);

82 void removeClient(SVGResourceClient*);

83

84 // Resolve a potentially external document reference.

85 void resolve(Document&);

86

87 // Returns the proxied element, or null if the proxy is invalid.

88 SVGElement* findElement(TreeScope&);

89

90 // Notify the proxy that the structure of the subtree rooted at the proxied

91 // element has mutated. This should generally only be called via a proxy set.

92 void contentChanged(TreeScope&);

93

94 const AtomicString& id() const { return m_id; }

95

96 DECLARE_VIRTUAL_TRACE();

97

98 private:

99 explicit SVGElementProxy(const AtomicString&);

100 SVGElementProxy(const String&, const AtomicString&);

101

102 TreeScope* treeScopeForLookup(TreeScope&) const;

103

104 class IdObserver;

105

106 HeapHashMap<Member<SVGResourceClient>, Member<IdObserver>> m_clients;

107 HeapHashMap<Member<TreeScope>, Member<IdObserver>> m_observers;

108 Member<DocumentResource> m_document;

109 AtomicString m_id;

110 // URL for resolving references to external resource documents. Contains an

111 // absolute URL to the resource to load. Cleared when a load has been

112 // initiated. Ignored if m_isLocal is true.

113 String m_url;

114 bool m_isLocal;

115 };

116

117 // Collection of SVGElementProxys. This is hosted by elements that can be

118 // subject to proxies (currently only SVGFilterElement), and is mainly a helper

119 // for dealing with the many-to-one structure of SVGElementProxy.

120 class SVGElementProxySet : public GarbageCollected<SVGElementProxySet> {

121 public:

122 void add(SVGElementProxy&);

123 bool isEmpty() const;

124

125 // Notify proxy clients that the (content of the) proxied element has

126 // changed.

127 void notifyContentChanged(TreeScope&);

128

129 DECLARE_TRACE();

130

131 private:

132 using ProxySet = HeapHashSet<WeakMember<SVGElementProxy>>;

133 ProxySet m_elementProxies;

134 };

135

136 } // namespace blink

137

138 #endif // SVGElementProxy_h

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