pkg/template_binding/lib/src/template.dart - sdk.git - Git at Google

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 part of template_binding;

 /** Extensions to [Element]s that behave as templates. */
 class TemplateBindExtension extends _ElementExtension {
   var _model;
   BindingDelegate _bindingDelegate;
   _TemplateIterator _iterator;
   bool _setModelScheduled = false;

   Element _templateInstanceRef;

   // Note: only used if `this is! TemplateElement`
   DocumentFragment _content;
   bool _templateIsDecorated;

   HtmlDocument _stagingDocument;

   _InstanceBindingMap _bindingMap;

   Node _refContent;

   TemplateBindExtension._(Element node) : super(node);

   Element get _node => super._node;

   TemplateBindExtension get _self => super._node is TemplateBindExtension
       ? _node : this;

   Bindable bind(String name, value, {bool oneTime: false}) {
     if (name != 'ref') return super.bind(name, value, oneTime: oneTime);


     var ref = oneTime ? value : value.open((ref) {
       _node.attributes['ref'] = ref;
       _refChanged();
     });

     _node.attributes['ref'] = ref;
     _refChanged();
     if (oneTime) return null;

     return _updateBindings('ref', value);
   }

   _TemplateIterator _processBindingDirectives(_TemplateBindingMap directives) {
     if (_iterator != null) _iterator._closeDependencies();

     if (directives._if == null &&
         directives._bind == null &&
         directives._repeat == null) {

       if (_iterator != null) {
         _iterator.close();
         _iterator = null;
       }
       return null;
     }

     if (_iterator == null) {
       _iterator = new _TemplateIterator(this);
     }

     _iterator._updateDependencies(directives, model);

     _templateObserver.observe(_node,
         attributes: true, attributeFilter: ['ref']);

     return _iterator;
   }

   /**
    * Creates an instance of the template, using the provided [model] and
    * optional binding [delegate].
    *
    * If [instanceBindings] is supplied, each [Bindable] in the returned
    * instance will be added to the list. This makes it easy to close all of the
    * bindings without walking the tree. This is not normally necesssary, but is
    * used internally by the system.
    */
   DocumentFragment createInstance([model, BindingDelegate delegate]) {
     if (delegate == null) delegate = _bindingDelegate;
     if (_refContent == null) _refContent = templateBind(_ref).content;

     var content = _refContent;
     if (content.firstChild == null) return _emptyInstance;

     final map = _getInstanceBindingMap(content, delegate);
     final staging = _getTemplateStagingDocument();
     final instance = _stagingDocument.createDocumentFragment();

     final instanceExt = new _InstanceExtension();
     _instanceExtension[instance] = instanceExt
       .._templateCreator = _node
       .._protoContent = content;

     final instanceRecord = new TemplateInstance(model);
     nodeBindFallback(instance)._templateInstance = instanceRecord;

     var i = 0;
     bool collectTerminator = false;
     for (var c = content.firstChild; c != null; c = c.nextNode, i++) {
       // The terminator of the instance is the clone of the last child of the
       // content. If the last child is an active template, it may produce
       // instances as a result of production, so simply collecting the last
       // child of the instance after it has finished producing may be wrong.
       if (c.nextNode == null) collectTerminator = true;

       final childMap = map != null ? map.getChild(i) : null;
       var clone = _cloneAndBindInstance(c, instance, _stagingDocument,
           childMap, model, delegate, instanceExt._bindings);

       nodeBindFallback(clone)._templateInstance = instanceRecord;
       if (collectTerminator) instanceExt._terminator = clone;
     }

     instanceRecord._firstNode = instance.firstChild;
     instanceRecord._lastNode = instance.lastChild;

     instanceExt._protoContent = null;
     instanceExt._templateCreator = null;
     return instance;
   }

   /** The data model which is inherited through the tree. */
   get model => _model;

   void set model(value) {
     _model = value;
     _ensureSetModelScheduled();
   }

   static Node _deepCloneIgnoreTemplateContent(Node node, stagingDocument) {
     var clone = stagingDocument.importNode(node, false);
     if (isSemanticTemplate(clone)) return clone;

     for (var c = node.firstChild; c != null; c = c.nextNode) {
       clone.append(_deepCloneIgnoreTemplateContent(c, stagingDocument));
     }
     return clone;
   }

   /**
    * The binding delegate which is inherited through the tree. It can be used
    * to configure custom syntax for `{{bindings}}` inside this template.
    */
   BindingDelegate get bindingDelegate => _bindingDelegate;


   void set bindingDelegate(BindingDelegate value) {
     if (_bindingDelegate != null) {
       throw new StateError('Template must be cleared before a new '
           'bindingDelegate can be assigned');
     }
     _bindingDelegate = value;

     // Clear cached state based on the binding delegate.
     _bindingMap = null;
     if (_iterator != null) {
       _iterator._initPrepareFunctions = false;
       _iterator._instanceModelFn = null;
       _iterator._instancePositionChangedFn = null;
     }
   }

   _ensureSetModelScheduled() {
     if (_setModelScheduled) return;
     _decorate();
     _setModelScheduled = true;
     scheduleMicrotask(_setModel);
   }

   void _setModel() {
     _setModelScheduled = false;
     var map = _getBindings(_node, _bindingDelegate);
     _processBindings(_node, map, _model);
   }

   _refChanged() {
     if (_iterator == null || _refContent == templateBind(_ref).content) return;

     _refContent = null;
     _iterator._valueChanged(null);
     _iterator._updateIteratedValue(null);
   }

   void clear() {
     _model = null;
     _bindingDelegate = null;
     if (bindings != null) {
       var ref = bindings.remove('ref');
       if (ref != null) ref.close();
     }
     _refContent = null;
     if (_iterator == null) return;
     _iterator._valueChanged(null);
     _iterator.close();
     _iterator = null;
   }

   /** Gets the template this node refers to. */
   Element get _ref {
     _decorate();

     var ref = _searchRefId(_node, _node.attributes['ref']);
     if (ref == null) {
       ref = _templateInstanceRef;
       if (ref == null) return _node;
     }

     var nextRef = templateBindFallback(ref)._ref;
     return nextRef != null ? nextRef : ref;
   }

   /**
    * Gets the content of this template.
    */
   DocumentFragment get content {
     _decorate();
     return _content != null ? _content : (_node as TemplateElement).content;
   }

   /**
    * Ensures proper API and content model for template elements.
    *
    * [instanceRef] can be used to set the [Element.ref] property of [template],
    * and use the ref's content will be used as source when createInstance() is
    * invoked.
    *
    * Returns true if this template was just decorated, or false if it was
    * already decorated.
    */
   static bool decorate(Element template, [Element instanceRef]) =>
       templateBindFallback(template)._decorate(instanceRef);

   bool _decorate([Element instanceRef]) {
     // == true check because it starts as a null field.
     if (_templateIsDecorated == true) return false;

     _injectStylesheet();
     _globalBaseUriWorkaround();

     var templateElementExt = this;
     _templateIsDecorated = true;
     var isNativeHtmlTemplate = _node is TemplateElement;
     final bootstrapContents = isNativeHtmlTemplate;
     final liftContents = !isNativeHtmlTemplate;
     var liftRoot = false;

     if (!isNativeHtmlTemplate) {
       if (_isAttributeTemplate(_node)) {
         if (instanceRef != null) {
           // Dart note: this is just an assert in JS.
           throw new ArgumentError('instanceRef should not be supplied for '
               'attribute templates.');
         }
         templateElementExt = templateBind(
             _extractTemplateFromAttributeTemplate(_node));
         templateElementExt._templateIsDecorated = true;
         isNativeHtmlTemplate = templateElementExt._node is TemplateElement;
         liftRoot = true;
       } else if (_isSvgTemplate(_node)) {
         templateElementExt = templateBind(
             _extractTemplateFromSvgTemplate(_node));
         templateElementExt._templateIsDecorated = true;
         isNativeHtmlTemplate = templateElementExt._node is TemplateElement;
       }
     }

     if (!isNativeHtmlTemplate) {
       var doc = _getOrCreateTemplateContentsOwner(templateElementExt._node);
       templateElementExt._content = doc.createDocumentFragment();
     }

     if (instanceRef != null) {
       // template is contained within an instance, its direct content must be
       // empty
       templateElementExt._templateInstanceRef = instanceRef;
     } else if (liftContents) {
       _liftNonNativeChildrenIntoContent(templateElementExt, _node, liftRoot);
     } else if (bootstrapContents) {
       bootstrap(templateElementExt.content);
     }

     return true;
   }

   static final _contentsOwner = new Expando();
   static final _ownerStagingDocument = new Expando();

   // http://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/templates/index.html#dfn-template-contents-owner
   static HtmlDocument _getOrCreateTemplateContentsOwner(Element template) {
     var doc = template.ownerDocument;
     if (doc.window == null) return doc;

     var d = _contentsOwner[doc];
     if (d == null) {
       // TODO(arv): This should either be a Document or HTMLDocument depending
       // on doc.
       d = doc.implementation.createHtmlDocument('');
       while (d.lastChild != null) {
         d.lastChild.remove();
       }
       _contentsOwner[doc] = d;
     }
     return d;
   }

   HtmlDocument _getTemplateStagingDocument() {
     if (_stagingDocument == null) {
       var owner = _node.ownerDocument;
       var doc = _ownerStagingDocument[owner];
       if (doc == null) {
         doc = owner.implementation.createHtmlDocument('');
         _isStagingDocument[doc] = true;
         _baseUriWorkaround(doc);
         _ownerStagingDocument[owner] = doc;
       }
       _stagingDocument = doc;
     }
     return _stagingDocument;
   }

   // For non-template browsers, the parser will disallow <template> in certain
   // locations, so we allow "attribute templates" which combine the template
   // element with the top-level container node of the content, e.g.
   //
   //   <tr template repeat="{{ foo }}"" class="bar"><td>Bar</td></tr>
   //
   // becomes
   //
   //   <template repeat="{{ foo }}">
   //   + #document-fragment
   //     + <tr class="bar">
   //       + <td>Bar</td>
   //
   static Element _extractTemplateFromAttributeTemplate(Element el) {
     var template = el.ownerDocument.createElement('template');
     el.parentNode.insertBefore(template, el);

     for (var name in el.attributes.keys.toList()) {
       switch (name) {
         case 'template':
           el.attributes.remove(name);
           break;
         case 'repeat':
         case 'bind':
         case 'ref':
           template.attributes[name] = el.attributes.remove(name);
           break;
       }
     }

     return template;
   }

   static Element _extractTemplateFromSvgTemplate(Element el) {
     var template = el.ownerDocument.createElement('template');
     el.parentNode.insertBefore(template, el);
     template.attributes.addAll(el.attributes);

     el.attributes.clear();
     el.remove();
     return template;
   }

   static void _liftNonNativeChildrenIntoContent(TemplateBindExtension template,
       Element el, bool useRoot) {

     var content = template.content;
     if (useRoot) {
       content.append(el);
       return;
     }

     var child;
     while ((child = el.firstChild) != null) {
       content.append(child);
     }
   }

   /**
    * This used to decorate recursively all templates from a given node.
    *
    * By default [decorate] will be called on templates lazily when certain
    * properties such as [model] are accessed, but it can be run eagerly to
    * decorate an entire tree recursively.
    */
   // TODO(rafaelw): Review whether this is the right public API.
   static void bootstrap(Node content) {
     void _bootstrap(template) {
       if (!TemplateBindExtension.decorate(template)) {
         bootstrap(templateBind(template).content);
       }
     }

     // Need to do this first as the contents may get lifted if |node| is
     // template.
     // TODO(jmesserly): content is DocumentFragment or Element
     var descendents =
         (content as dynamic).querySelectorAll(_allTemplatesSelectors);
     if (isSemanticTemplate(content)) {
       _bootstrap(content);
     }

     descendents.forEach(_bootstrap);
   }

   static final String _allTemplatesSelectors =
       'template, ' +
       _SEMANTIC_TEMPLATE_TAGS.keys.map((k) => "$k[template]").join(", ");

   static bool _initStyles;

   // This is to replicate template_element.css
   // TODO(jmesserly): move this to an opt-in CSS file?
   static void _injectStylesheet() {
     if (_initStyles == true) return;
     _initStyles = true;

     var style = new StyleElement()
         ..text = '$_allTemplatesSelectors { display: none; }';
     document.head.append(style);
   }

   static bool _initBaseUriWorkaround;

   static void _globalBaseUriWorkaround() {
     if (_initBaseUriWorkaround == true) return;
     _initBaseUriWorkaround = true;

     var t = document.createElement('template');
     if (t is TemplateElement) {
       var d = t.content.ownerDocument;
       if (d.documentElement == null) {
         d.append(d.createElement('html')).append(d.createElement('head'));
       }
       // don't patch this if TemplateBinding.js already has.
       if (d.head.querySelector('base') == null) {
         _baseUriWorkaround(d);
       }
     }
   }

   // TODO(rafaelw): Remove when fix for
   // https://codereview.chromium.org/164803002/
   // makes it to Chrome release.
   static void _baseUriWorkaround(HtmlDocument doc) {
     BaseElement base = doc.createElement('base');
     base.href = document.baseUri;
     doc.head.append(base);
   }

   static final _templateObserver = new MutationObserver((records, _) {
     for (MutationRecord record in records) {
       templateBindFallback(record.target)._refChanged();
     }
   });

 }

 final DocumentFragment _emptyInstance = () {
   var empty = new DocumentFragment();
   _instanceExtension[empty] = new _InstanceExtension();
   return empty;
 }();

 // TODO(jmesserly): if we merged with wtih TemplateInstance, it seems like it
 // would speed up some operations (e.g. _getInstanceRoot wouldn't need to walk
 // the parent chain).
 class _InstanceExtension {
   final List _bindings = [];
   Node _terminator;
   Element _templateCreator;
   DocumentFragment _protoContent;
 }

 // TODO(jmesserly): this is private in JS but public for us because pkg:polymer
 // uses it.
 List getTemplateInstanceBindings(DocumentFragment fragment) {
   var ext = _instanceExtension[fragment];
   return ext != null ? ext._bindings : ext;
 }

 /// Gets the root of the current node's parent chain
 _getFragmentRoot(Node node) {
   var p;
   while ((p = node.parentNode) != null) {
     node = p;
   }
   return node;
 }

 Node _searchRefId(Node node, String id) {
   if (id == null || id == '') return null;

   final selector = '#$id';
   while (true) {
     node = _getFragmentRoot(node);

     Node ref = null;

     _InstanceExtension instance = _instanceExtension[node];
     if (instance != null && instance._protoContent != null) {
       ref = instance._protoContent.querySelector(selector);
     } else if (_hasGetElementById(node)) {
       ref = (node as dynamic).getElementById(id);
     }

     if (ref != null) return ref;

     if (instance == null) return null;
     node = instance._templateCreator;
     if (node == null) return null;
   }
 }

 _getInstanceRoot(node) {
   while (node.parentNode != null) {
     node = node.parentNode;
   }
   _InstanceExtension instance = _instanceExtension[node];
   return instance != null && instance._templateCreator != null ? node : null;
 }

 final Expando<_InstanceExtension> _instanceExtension = new Expando();

 final _isStagingDocument = new Expando();
	// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	part of template_binding;

	/** Extensions to [Element]s that behave as templates. */
	class TemplateBindExtension extends _ElementExtension {
	var _model;
	BindingDelegate _bindingDelegate;
	_TemplateIterator _iterator;
	bool _setModelScheduled = false;

	Element _templateInstanceRef;

	// Note: only used if `this is! TemplateElement`
	DocumentFragment _content;
	bool _templateIsDecorated;

	HtmlDocument _stagingDocument;

	_InstanceBindingMap _bindingMap;

	Node _refContent;

	TemplateBindExtension._(Element node) : super(node);

	Element get _node => super._node;

	TemplateBindExtension get _self => super._node is TemplateBindExtension
	? _node : this;

	Bindable bind(String name, value, {bool oneTime: false}) {
	if (name != 'ref') return super.bind(name, value, oneTime: oneTime);


	var ref = oneTime ? value : value.open((ref) {
	_node.attributes['ref'] = ref;
	_refChanged();
	});

	_node.attributes['ref'] = ref;
	_refChanged();
	if (oneTime) return null;

	return _updateBindings('ref', value);
	}

	_TemplateIterator _processBindingDirectives(_TemplateBindingMap directives) {
	if (_iterator != null) _iterator._closeDependencies();

	if (directives._if == null &&
	directives._bind == null &&
	directives._repeat == null) {

	if (_iterator != null) {
	_iterator.close();
	_iterator = null;
	}
	return null;
	}

	if (_iterator == null) {
	_iterator = new _TemplateIterator(this);
	}

	_iterator._updateDependencies(directives, model);

	_templateObserver.observe(_node,
	attributes: true, attributeFilter: ['ref']);

	return _iterator;
	}

	/**
	* Creates an instance of the template, using the provided [model] and
	* optional binding [delegate].
	*
	* If [instanceBindings] is supplied, each [Bindable] in the returned
	* instance will be added to the list. This makes it easy to close all of the
	* bindings without walking the tree. This is not normally necesssary, but is
	* used internally by the system.
	*/
	DocumentFragment createInstance([model, BindingDelegate delegate]) {
	if (delegate == null) delegate = _bindingDelegate;
	if (_refContent == null) _refContent = templateBind(_ref).content;

	var content = _refContent;
	if (content.firstChild == null) return _emptyInstance;

	final map = _getInstanceBindingMap(content, delegate);
	final staging = _getTemplateStagingDocument();
	final instance = _stagingDocument.createDocumentFragment();

	final instanceExt = new _InstanceExtension();
	_instanceExtension[instance] = instanceExt
	.._templateCreator = _node
	.._protoContent = content;

	final instanceRecord = new TemplateInstance(model);
	nodeBindFallback(instance)._templateInstance = instanceRecord;

	var i = 0;
	bool collectTerminator = false;
	for (var c = content.firstChild; c != null; c = c.nextNode, i++) {
	// The terminator of the instance is the clone of the last child of the
	// content. If the last child is an active template, it may produce
	// instances as a result of production, so simply collecting the last
	// child of the instance after it has finished producing may be wrong.
	if (c.nextNode == null) collectTerminator = true;

	final childMap = map != null ? map.getChild(i) : null;
	var clone = _cloneAndBindInstance(c, instance, _stagingDocument,
	childMap, model, delegate, instanceExt._bindings);

	nodeBindFallback(clone)._templateInstance = instanceRecord;
	if (collectTerminator) instanceExt._terminator = clone;
	}

	instanceRecord._firstNode = instance.firstChild;
	instanceRecord._lastNode = instance.lastChild;

	instanceExt._protoContent = null;
	instanceExt._templateCreator = null;
	return instance;
	}

	/** The data model which is inherited through the tree. */
	get model => _model;

	void set model(value) {
	_model = value;
	_ensureSetModelScheduled();
	}

	static Node _deepCloneIgnoreTemplateContent(Node node, stagingDocument) {
	var clone = stagingDocument.importNode(node, false);
	if (isSemanticTemplate(clone)) return clone;

	for (var c = node.firstChild; c != null; c = c.nextNode) {
	clone.append(_deepCloneIgnoreTemplateContent(c, stagingDocument));
	}
	return clone;
	}

	/**
	* The binding delegate which is inherited through the tree. It can be used
	* to configure custom syntax for `{{bindings}}` inside this template.
	*/
	BindingDelegate get bindingDelegate => _bindingDelegate;


	void set bindingDelegate(BindingDelegate value) {
	if (_bindingDelegate != null) {
	throw new StateError('Template must be cleared before a new '
	'bindingDelegate can be assigned');
	}
	_bindingDelegate = value;

	// Clear cached state based on the binding delegate.
	_bindingMap = null;
	if (_iterator != null) {
	_iterator._initPrepareFunctions = false;
	_iterator._instanceModelFn = null;
	_iterator._instancePositionChangedFn = null;
	}
	}

	_ensureSetModelScheduled() {
	if (_setModelScheduled) return;
	_decorate();
	_setModelScheduled = true;
	scheduleMicrotask(_setModel);
	}

	void _setModel() {
	_setModelScheduled = false;
	var map = _getBindings(_node, _bindingDelegate);
	_processBindings(_node, map, _model);
	}

	_refChanged() {
	if (_iterator == null \|\| _refContent == templateBind(_ref).content) return;

	_refContent = null;
	_iterator._valueChanged(null);
	_iterator._updateIteratedValue(null);
	}

	void clear() {
	_model = null;
	_bindingDelegate = null;
	if (bindings != null) {
	var ref = bindings.remove('ref');
	if (ref != null) ref.close();
	}
	_refContent = null;
	if (_iterator == null) return;
	_iterator._valueChanged(null);
	_iterator.close();
	_iterator = null;
	}

	/** Gets the template this node refers to. */
	Element get _ref {
	_decorate();

	var ref = _searchRefId(_node, _node.attributes['ref']);
	if (ref == null) {
	ref = _templateInstanceRef;
	if (ref == null) return _node;
	}

	var nextRef = templateBindFallback(ref)._ref;
	return nextRef != null ? nextRef : ref;
	}

	/**
	* Gets the content of this template.
	*/
	DocumentFragment get content {
	_decorate();
	return _content != null ? _content : (_node as TemplateElement).content;
	}

	/**
	* Ensures proper API and content model for template elements.
	*
	* [instanceRef] can be used to set the [Element.ref] property of [template],
	* and use the ref's content will be used as source when createInstance() is
	* invoked.
	*
	* Returns true if this template was just decorated, or false if it was
	* already decorated.
	*/
	static bool decorate(Element template, [Element instanceRef]) =>
	templateBindFallback(template)._decorate(instanceRef);

	bool _decorate([Element instanceRef]) {
	// == true check because it starts as a null field.
	if (_templateIsDecorated == true) return false;

	_injectStylesheet();
	_globalBaseUriWorkaround();

	var templateElementExt = this;
	_templateIsDecorated = true;
	var isNativeHtmlTemplate = _node is TemplateElement;
	final bootstrapContents = isNativeHtmlTemplate;
	final liftContents = !isNativeHtmlTemplate;
	var liftRoot = false;

	if (!isNativeHtmlTemplate) {
	if (_isAttributeTemplate(_node)) {
	if (instanceRef != null) {
	// Dart note: this is just an assert in JS.
	throw new ArgumentError('instanceRef should not be supplied for '
	'attribute templates.');
	}
	templateElementExt = templateBind(
	_extractTemplateFromAttributeTemplate(_node));
	templateElementExt._templateIsDecorated = true;
	isNativeHtmlTemplate = templateElementExt._node is TemplateElement;
	liftRoot = true;
	} else if (_isSvgTemplate(_node)) {
	templateElementExt = templateBind(
	_extractTemplateFromSvgTemplate(_node));
	templateElementExt._templateIsDecorated = true;
	isNativeHtmlTemplate = templateElementExt._node is TemplateElement;
	}
	}

	if (!isNativeHtmlTemplate) {
	var doc = _getOrCreateTemplateContentsOwner(templateElementExt._node);
	templateElementExt._content = doc.createDocumentFragment();
	}

	if (instanceRef != null) {
	// template is contained within an instance, its direct content must be
	// empty
	templateElementExt._templateInstanceRef = instanceRef;
	} else if (liftContents) {
	_liftNonNativeChildrenIntoContent(templateElementExt, _node, liftRoot);
	} else if (bootstrapContents) {
	bootstrap(templateElementExt.content);
	}

	return true;
	}

	static final _contentsOwner = new Expando();
	static final _ownerStagingDocument = new Expando();

	// http://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/templates/index.html#dfn-template-contents-owner
	static HtmlDocument _getOrCreateTemplateContentsOwner(Element template) {
	var doc = template.ownerDocument;
	if (doc.window == null) return doc;

	var d = _contentsOwner[doc];
	if (d == null) {
	// TODO(arv): This should either be a Document or HTMLDocument depending
	// on doc.
	d = doc.implementation.createHtmlDocument('');
	while (d.lastChild != null) {
	d.lastChild.remove();
	}
	_contentsOwner[doc] = d;
	}
	return d;
	}

	HtmlDocument _getTemplateStagingDocument() {
	if (_stagingDocument == null) {
	var owner = _node.ownerDocument;
	var doc = _ownerStagingDocument[owner];
	if (doc == null) {
	doc = owner.implementation.createHtmlDocument('');
	_isStagingDocument[doc] = true;
	_baseUriWorkaround(doc);
	_ownerStagingDocument[owner] = doc;
	}
	_stagingDocument = doc;
	}
	return _stagingDocument;
	}

	// For non-template browsers, the parser will disallow <template> in certain
	// locations, so we allow "attribute templates" which combine the template
	// element with the top-level container node of the content, e.g.
	//
	// <tr template repeat="{{ foo }}"" class="bar"><td>Bar</td></tr>
	//
	// becomes
	//
	// <template repeat="{{ foo }}">
	// + #document-fragment
	// + <tr class="bar">
	// + <td>Bar</td>
	//
	static Element _extractTemplateFromAttributeTemplate(Element el) {
	var template = el.ownerDocument.createElement('template');
	el.parentNode.insertBefore(template, el);

	for (var name in el.attributes.keys.toList()) {
	switch (name) {
	case 'template':
	el.attributes.remove(name);
	break;
	case 'repeat':
	case 'bind':
	case 'ref':
	template.attributes[name] = el.attributes.remove(name);
	break;
	}
	}

	return template;
	}

	static Element _extractTemplateFromSvgTemplate(Element el) {
	var template = el.ownerDocument.createElement('template');
	el.parentNode.insertBefore(template, el);
	template.attributes.addAll(el.attributes);

	el.attributes.clear();
	el.remove();
	return template;
	}

	static void _liftNonNativeChildrenIntoContent(TemplateBindExtension template,
	Element el, bool useRoot) {

	var content = template.content;
	if (useRoot) {
	content.append(el);
	return;
	}

	var child;
	while ((child = el.firstChild) != null) {
	content.append(child);
	}
	}

	/**
	* This used to decorate recursively all templates from a given node.
	*
	* By default [decorate] will be called on templates lazily when certain
	* properties such as [model] are accessed, but it can be run eagerly to
	* decorate an entire tree recursively.
	*/
	// TODO(rafaelw): Review whether this is the right public API.
	static void bootstrap(Node content) {
	void _bootstrap(template) {
	if (!TemplateBindExtension.decorate(template)) {
	bootstrap(templateBind(template).content);
	}
	}

	// Need to do this first as the contents may get lifted if \|node\| is
	// template.
	// TODO(jmesserly): content is DocumentFragment or Element
	var descendents =
	(content as dynamic).querySelectorAll(_allTemplatesSelectors);
	if (isSemanticTemplate(content)) {
	_bootstrap(content);
	}

	descendents.forEach(_bootstrap);
	}

	static final String _allTemplatesSelectors =
	'template, ' +
	_SEMANTIC_TEMPLATE_TAGS.keys.map((k) => "$k[template]").join(", ");

	static bool _initStyles;

	// This is to replicate template_element.css
	// TODO(jmesserly): move this to an opt-in CSS file?
	static void _injectStylesheet() {
	if (_initStyles == true) return;
	_initStyles = true;

	var style = new StyleElement()
	..text = '$_allTemplatesSelectors { display: none; }';
	document.head.append(style);
	}

	static bool _initBaseUriWorkaround;

	static void _globalBaseUriWorkaround() {
	if (_initBaseUriWorkaround == true) return;
	_initBaseUriWorkaround = true;

	var t = document.createElement('template');
	if (t is TemplateElement) {
	var d = t.content.ownerDocument;
	if (d.documentElement == null) {
	d.append(d.createElement('html')).append(d.createElement('head'));
	}
	// don't patch this if TemplateBinding.js already has.
	if (d.head.querySelector('base') == null) {
	_baseUriWorkaround(d);
	}
	}
	}

	// TODO(rafaelw): Remove when fix for
	// https://codereview.chromium.org/164803002/
	// makes it to Chrome release.
	static void _baseUriWorkaround(HtmlDocument doc) {
	BaseElement base = doc.createElement('base');
	base.href = document.baseUri;
	doc.head.append(base);
	}

	static final _templateObserver = new MutationObserver((records, _) {
	for (MutationRecord record in records) {
	templateBindFallback(record.target)._refChanged();
	}
	});

	}

	final DocumentFragment _emptyInstance = () {
	var empty = new DocumentFragment();
	_instanceExtension[empty] = new _InstanceExtension();
	return empty;
	}();

	// TODO(jmesserly): if we merged with wtih TemplateInstance, it seems like it
	// would speed up some operations (e.g. _getInstanceRoot wouldn't need to walk
	// the parent chain).
	class _InstanceExtension {
	final List _bindings = [];
	Node _terminator;
	Element _templateCreator;
	DocumentFragment _protoContent;
	}

	// TODO(jmesserly): this is private in JS but public for us because pkg:polymer
	// uses it.
	List getTemplateInstanceBindings(DocumentFragment fragment) {
	var ext = _instanceExtension[fragment];
	return ext != null ? ext._bindings : ext;
	}

	/// Gets the root of the current node's parent chain
	_getFragmentRoot(Node node) {
	var p;
	while ((p = node.parentNode) != null) {
	node = p;
	}
	return node;
	}

	Node _searchRefId(Node node, String id) {
	if (id == null \|\| id == '') return null;

	final selector = '#$id';
	while (true) {
	node = _getFragmentRoot(node);

	Node ref = null;

	_InstanceExtension instance = _instanceExtension[node];
	if (instance != null && instance._protoContent != null) {
	ref = instance._protoContent.querySelector(selector);
	} else if (_hasGetElementById(node)) {
	ref = (node as dynamic).getElementById(id);
	}

	if (ref != null) return ref;

	if (instance == null) return null;
	node = instance._templateCreator;
	if (node == null) return null;
	}
	}

	_getInstanceRoot(node) {
	while (node.parentNode != null) {
	node = node.parentNode;
	}
	_InstanceExtension instance = _instanceExtension[node];
	return instance != null && instance._templateCreator != null ? node : null;
	}

	final Expando<_InstanceExtension> _instanceExtension = new Expando();

	final _isStagingDocument = new Expando();