1/*
2 * Copyright (C) 2013 Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met:
7 *
8 *     * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *     * Redistributions in binary form must reproduce the above
11 * copyright notice, this list of conditions and the following disclaimer
12 * in the documentation and/or other materials provided with the
13 * distribution.
14 *     * Neither the name of Google Inc. nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#ifndef HTMLImport_h
32#define HTMLImport_h
33
34#include "core/html/imports/HTMLImportState.h"
35#include "platform/heap/Handle.h"
36#include "wtf/TreeNode.h"
37
38namespace blink {
39
40class Document;
41class LocalFrame;
42class HTMLImportChild;
43class HTMLImportLoader;
44class HTMLImportsController;
45class KURL;
46
47//
48// # Basic Data Structure and Algorithms of HTML Imports implemenation.
49//
50// ## The Import Tree
51//
52// HTML Imports form a tree:
53//
54// * The root of the tree is HTMLImportTreeRoot.
55//
56// * The HTMLImportTreeRoot is owned HTMLImportsController, which is owned by the master
57//   document as a DocumentSupplement.
58//
59// * The non-root nodes are HTMLImportChild. They are all owned by HTMLImporTreeRoot.
60//   LinkStyle is wired into HTMLImportChild by implementing HTMLImportChildClient interface
61//
62// * Both HTMLImportTreeRoot and HTMLImportChild are derived from HTMLImport superclass
63//   that models the tree data structure using WTF::TreeNode and provides a set of
64//   virtual functions.
65//
66// HTMLImportsController also owns all loaders in the tree and manages their lifetime through it.
67// One assumption is that the tree is append-only and nodes are never inserted in the middle of the tree nor removed.
68//
69// Full diagram is here:
70// https://docs.google.com/drawings/d/1jFQrO0IupWrlykTNzQ3Nv2SdiBiSz4UE9-V3-vDgBb0/
71//
72// # Import Sharing and HTMLImportLoader
73//
74// The HTML Imports spec calls for de-dup mechanism to share already loaded imports.
75// To implement this, the actual loading machinery is split out from HTMLImportChild to
76// HTMLImportLoader, and each loader shares HTMLImportLoader with other loader if the URL is same.
77// Check around HTMLImportsController::findLink() for more detail.
78//
79// HTMLImportLoader can be shared by multiple imports.
80//
81//    HTMLImportChild (1)-->(*) HTMLImportLoader
82//
83//
84// # Script Blocking
85//
86// - An import blocks the HTML parser of its own imported document from running <script>
87//   until all of its children are loaded.
88//   Note that dynamically added import won't block the parser.
89//
90// - An import under loading also blocks imported documents that follow from being created.
91//   This is because an import can include another import that has same URLs of following ones.
92//   In such case, the preceding import should be loaded and following ones should be de-duped.
93//
94
95// The superclass of HTMLImportTreeRoot and HTMLImportChild
96// This represents the import tree data structure.
97class HTMLImport : public NoBaseWillBeGarbageCollectedFinalized<HTMLImport>, public TreeNode<HTMLImport> {
98public:
99    enum SyncMode {
100        Sync  = 0,
101        Async = 1
102    };
103
104    virtual ~HTMLImport() { }
105
106    // FIXME: Consider returning HTMLImportTreeRoot.
107    HTMLImport* root();
108    bool precedes(HTMLImport*);
109    bool isRoot() const { return !parent(); }
110    bool isSync() const { return SyncMode(m_sync) == Sync; }
111    bool formsCycle() const;
112    const HTMLImportState& state() const { return m_state; }
113
114    void appendImport(HTMLImport*);
115
116    virtual Document* document() const = 0;
117    virtual bool isDone() const = 0; // FIXME: Should be renamed to haveFinishedLoading()
118    virtual HTMLImportLoader* loader() const { return 0; }
119    virtual void stateWillChange() { }
120    virtual void stateDidChange();
121
122    virtual void trace(Visitor*) { }
123
124protected:
125    // Stating from most conservative state.
126    // It will be corrected through state update flow.
127    explicit HTMLImport(SyncMode sync)
128        : m_sync(sync)
129    { }
130
131    static void recalcTreeState(HTMLImport* root);
132
133#if !defined(NDEBUG)
134    void show();
135    void showTree(HTMLImport* highlight, unsigned depth);
136    virtual void showThis();
137#endif
138
139private:
140    HTMLImportState m_state;
141    unsigned m_sync : 1;
142};
143
144} // namespace blink
145
146#endif // HTMLImport_h
147