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Unified Diff: third_party/WebKit/Source/core/svg/SVGElementProxy.h

Issue 2401343002: Tracking filter mutation via SVGElementProxy (Closed)
Patch Set: referenceChanged -> proxiedElementChanged Created 4 years, 2 months ago
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Index: third_party/WebKit/Source/core/svg/SVGElementProxy.h
diff --git a/third_party/WebKit/Source/core/svg/SVGElementProxy.h b/third_party/WebKit/Source/core/svg/SVGElementProxy.h
new file mode 100644
index 0000000000000000000000000000000000000000..8ede10cbb56738c656ff04fb7414e48e9bd07364
--- /dev/null
+++ b/third_party/WebKit/Source/core/svg/SVGElementProxy.h
@@ -0,0 +1,166 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SVGElementProxy_h
+#define SVGElementProxy_h
+
+#include "core/fetch/DocumentResource.h"
+#include "platform/heap/Handle.h"
+#include "wtf/text/AtomicString.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+class Document;
+class SVGElement;
+class SVGResourceClient;
+class TreeScope;
+
+// A proxy to an SVGElement. Allows access to an element with a certain 'id',
+// and provides its clients with notifications when the proxied element
+// changes.
+//
+// SVGElements can be referenced using CSS, for example like:
+//
+// filter: url(#baz);
+//
+// or
+//
+// filter: url(foo.com/bar.svg#baz);
+//
+// SVGElementProxy provide a mechanism to persistently reference an SVGElement
+// in such cases - regardless of if the proxied element reside in the same
+// document (read: tree scope) or in an external (resource) document. In the
+// latter case, SVGElementProxy will transparently take care of the loading of
+// the document (if requested, see SVGElementProxy::resolve.)
+//
+// The proxy uses an 'id' (c.f getElementById) to determine which element to
+// proxy. The id is looked up in the TreeScope of the element for a
+// same-document reference and in the TreeScope of the Document for a external
+// document reference.
+//
+// For same document references, the proxy will track changes that could affect
+// the 'id' lookup, to handle elements being added, removed or having their
+// 'id' mutated. (This does not apply for the external document case because
+// it's assumed they will not mutate after load, due to scripts not being run
+// et.c.)
+//
+// SVGElementProxys are created by CSSURIValue, and have SVGResourceClients as
+// a means to deliver change notifications. Clients that are interested in
+// change notifications hence need to register a SVGResourceClient with the
+// proxy. Most commonly this registration would take place when the
+// ComputedStyle changes.
+//
+// Registration of a client does not establish a link to the proxied element
+// right away. That is instead deferred until element(...) is called on the
+// SVGElementProxy. At this point, the proxy will be registered with either the
+// element (on success) or a set of "pending proxies" managed by
+// SVGDocumentExtensions. (For external references lookups will not be
+// registered, per the same assumption as mentioned above.)
+//
+// As content is mutated, clients will get notified via the proxied element
+// which in turn will notify all registered proxies, which will notify all
+// registered clients.
+//
+// <event> -> SVG...Element -> SVGElementProxy(0..N) -> SVGResourceClient(0..N)
+//
+class SVGElementProxy : public GarbageCollectedFinalized<SVGElementProxy>,
+ private DocumentResourceClient {
+ USING_GARBAGE_COLLECTED_MIXIN(SVGElementProxy);
+ USING_PRE_FINALIZER(SVGElementProxy, detachDocumentClient);
+
+ public:
+ // Create a proxy to an element in the same document. (See also
+ // SVGURLReferenceResolver and the definition of 'local url'.)
+ static SVGElementProxy* create(const AtomicString& id) {
+ return new SVGElementProxy(id);
+ }
+
+ // Create a proxy to an element in a different document (indicated by |url|.)
+ static SVGElementProxy* create(const String& url, const AtomicString& id) {
+ return new SVGElementProxy(url, id);
+ }
+ virtual ~SVGElementProxy();
+
+ void addClient(SVGResourceClient*);
+ void removeClient(SVGResourceClient*);
+
+ // Resolve a potentially external document reference.
+ void resolve(Document&);
+
+ // Returns the proxied element, or null if the proxy is invalid.
+ SVGElement* element(TreeScope&);
esprehn 2016/10/25 01:18:42 getElement or findElement?
fs 2016/10/25 15:00:53 Done.
+
+ // Notify the proxy that the structure of the subtree rooted at the proxied
+ // element has mutated. This should generally only be called via a proxy
+ // tracker.
+ void contentChanged();
+
+ // Notify the proxy that the reference to the proxied element may now be
+ // pointing somewhere else (the id of an element changed, the resource
+ // document of the proxy finished loading, the element was removed from the
+ // document tree etc.) This should generally only be called via a proxy
+ // tracker.
+ void proxiedElementChanged();
+
+ const AtomicString& id() const { return m_id; }
+
+ // The current "generation" of this proxy. This is essentially a sequence
+ // number (or counter) incremented with each change to the proxied element
+ // (or its descendants, although that depends on the type of element being
+ // proxied.)
+ unsigned generation() const { return m_generation; }
esprehn 2016/10/25 01:18:42 I'd prefer a dirty bit specific to the subtree or
fs 2016/10/25 15:00:53 This mechanism is only here for the case of the ta
+
+ DECLARE_VIRTUAL_TRACE();
+
+ private:
+ explicit SVGElementProxy(const AtomicString&);
+ SVGElementProxy(const String&, const AtomicString&);
+
+ void detachDocumentClient();
+ // ResourceClient implementation. Used when referencing an external resource
+ // document.
+ void notifyFinished(Resource*) override;
+ String debugName() const override { return "SVGElementProxy"; }
+
+ void incrementGeneration() { m_generation++; }
+ TreeScope* treeScopeForLookup(TreeScope&) const;
+
+ HeapHashSet<Member<SVGResourceClient>> m_clients;
+ Member<DocumentResource> m_document;
+ AtomicString m_id;
+ // URL for resolving references to external resource documents. Contains an
+ // absolute URL to the resource to load. Cleared when a load has been
+ // initiated. Ignored if m_isLocal is true.
+ String m_url;
+ unsigned m_generation;
+ bool m_isLocal;
+};
+
+// Collection of SVGElementProxys. This is hosted by elements that can be
+// subject to proxies (currently only SVGFilterElement), and is mainly a helper
+// for dealing with the many-to-one structure of SVGElementProxy.
+class SVGElementProxySet : public GarbageCollected<SVGElementProxySet> {
+ public:
+ void add(SVGElementProxy&);
+ bool isEmpty() const;
+
+ // Notify proxy clients that the (content of the) proxied element has
+ // changed.
+ void notifyContentChanged();
+
+ // Notify proxy clients that the reference to the proxied element is no
+ // longer valid. This also clears references to the proxied element.
+ void invalidateProxies();
+
+ DECLARE_TRACE();
+
+ private:
+ using ProxySet = HeapHashSet<WeakMember<SVGElementProxy>>;
+ ProxySet m_elementProxies;
+};
+
+} // namespace blink
+
+#endif // SVGElementProxy_h

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