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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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