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34 #include "core/html/imports/HTMLImportState.h"
35 #include "platform/heap/Handle.h"
36 #include "wtf/TreeNode.h"
42 class HTMLImportChild;
43 class HTMLImportLoader;
44 class HTMLImportsController;
48 // # Basic Data Structure and Algorithms of HTML Imports implemenation.
52 // HTML Imports form a tree:
54 // * The root of the tree is HTMLImportTreeRoot.
56 // * The HTMLImportTreeRoot is owned HTMLImportsController, which is owned by the master
57 // document as a DocumentSupplement.
59 // * The non-root nodes are HTMLImportChild. They are all owned by HTMLImporTreeRoot.
60 // LinkStyle is wired into HTMLImportChild by implementing HTMLImportChildClient interface
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
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.
69 // Full diagram is here:
70 // https://docs.google.com/drawings/d/1jFQrO0IupWrlykTNzQ3Nv2SdiBiSz4UE9-V3-vDgBb0/
72 // # Import Sharing and HTMLImportLoader
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.
79 // HTMLImportLoader can be shared by multiple imports.
81 // HTMLImportChild (1)-->(*) HTMLImportLoader
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.
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.
95 // The superclass of HTMLImportTreeRoot and HTMLImportChild
96 // This represents the import tree data structure.
97 class HTMLImport : public NoBaseWillBeGarbageCollectedFinalized<HTMLImport>, public TreeNode<HTMLImport> {
104 virtual ~HTMLImport() { }
106 // FIXME: Consider returning HTMLImportTreeRoot.
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; }
114 void appendImport(HTMLImport*);
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();
122 virtual void trace(Visitor*) { }
125 // Stating from most conservative state.
126 // It will be corrected through state update flow.
127 explicit HTMLImport(SyncMode sync)
131 static void recalcTreeState(HTMLImport* root);
135 void showTree(HTMLImport* highlight, unsigned depth);
136 virtual void showThis();
140 HTMLImportState m_state;
146 #endif // HTMLImport_h