[ADD] core Traverser API

There are still questions over how it'll work, and if it can work at all

bzr revid: xmo@openerp.com-20120301102117-zxd89ffcvo2n32nw

addons/web/static/src/js/data.js

@@ -261,6 +261,85 @@ openerp.web.Model = openerp.web.Class.extend(/** @lends openerp.web.Model# */{
     },
 });
 
+openerp.web.Traverser = openerp.web.Class.extend(/** @lends openerp.web.Traverser# */{
+    /**
+     * @constructs openerp.web.Traverser
+     * @extends openerp.web.Class
+     *
+     * @param {openerp.web.Model} model instance this traverser is bound to
+     */
+    init: function (model) {
+        this._model = model;
+        this._index = 0;
+    },
+
+    /**
+     * Gets and sets the current index
+     *
+     * @param {Number} [idx]
+     * @returns {Number} current index
+     */
+    index: function (idx) {
+        if (idx) { this._index = idx; }
+        return this._index;
+    },
+    /**
+     * Returns the model this traverser is currently bound to
+     *
+     * @returns {openerp.web.Model}
+     */
+    model: function () {
+        return this._model;
+    },
+    /**
+     * Fetches the size of the backing model's match
+     *
+     * @returns {Deferred<Number>} deferred count
+     */
+    size: function () {
+        return this._model.query().count();
+    },
+
+    /**
+     * Record at the current index for the collection, fails if there is no
+     * record at the current index.
+     *
+     * @returns {Deferred<>}
+     */
+    current: function (fields) {
+        return this._model.query(fields).first().pipe(function (record) {
+            if (record == null) {
+                return $.Deferred()
+                    .reject('No record at index' + this._index)
+                    .promise();
+            }
+            return record;
+        });
+    },
+    next: function (fields) {
+        var self = this;
+        this._index++;
+        return this.size().pipe(function (s) {
+            if (self._index >= s) {
+                self._index = 0;
+            }
+            return self.current(fields);
+        });
+    },
+    previous: function (fields) {
+        var self = this;
+        this._index--;
+        if (this._index < 0) {
+            return this.size().pipe(function (s) {
+                self._index = s-1;
+                return self.current(fields);
+            });
+        }
+        return this.current(fields);
+    }
+
+});
+
 openerp.web.DataGroup =  openerp.web.OldWidget.extend( /** @lends openerp.web.DataGroup# */{
     /**
      * Management interface between views and grouped collections of OpenERP

doc/source/rpc.rst

@@ -170,6 +170,75 @@ around and use them differently/add new specifications on them.
        (``?`` field) and the inability to "drill down" into relations
        for sorting.
 
+Synchronizing views (provisional)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. note:: this API may not be final, and may not even remain
+
+While the high-level RPC API is mostly stateless, some objects in
+OpenERP Web need to share state information. One of those is OpenERP
+views, especially between "collection-based" views (lists, graphs) and
+"record-based" views (forms, diagrams), which gets its very own API
+for traversing collections of records, the aptly-named
+:js:class:`~openerp.web.Traverser`.
+
+A :js:class:`~openerp.web.Traverser` is linked to a
+:js:class:`~openerp.web.Model` and is used to iterate over it
+asynchronously (and using indexes).
+
+.. js:class:: openerp.web.Traverser(model)
+
+    .. js:function:: openerp.web.Traverser.model()
+
+        :returns: the :js:class:`~openerp.web.Model` this traverser
+                  instance is bound to
+
+    .. js:function:: openerp.web.Traverser.index([idx])
+
+        If provided with an index parameter, sets that as the new
+        index for the traverser.
+
+        :param Number idx: the new index for the traverser
+        :returns: the current index for the traverser
+
+    .. js:function:: openerp.web.Traverser.current([fields])
+
+        Fetches the traverser's "current" record (that is, the record
+        at the current index of the traverser)
+
+        :param Array<String> fields: fields to return in the record
+        :rtype: Deferred<>
+
+    .. js:function:: openerp.web.Traverser.next([fields])
+
+        Increases the traverser's internal index by one, the fetches
+        the corresponding record. Roughly equivalent to:
+
+        .. code-block:: javascript
+
+            var idx = traverser.index();
+            traverser.index(idx+1);
+            traverser.current();
+
+        :param Array<String> fields: fields to return in the record
+        :rtype: Deferred<>
+
+    .. js:function:: openerp.web.Traverser.previous([fields])
+
+        Similar to :js:func:`~openerp.web.Traverser.next` but iterates
+        the traverser backwards rather than forward.
+
+        :param Array<String> fields: fields to return in the record
+        :rtype: Deferred<>
+
+    .. js:function:: openerp.web.Traverser.size()
+
+        Shortcut to checking the size of the backing model, calling
+        ``traverser.size()`` is equivalent to calling
+        ``traverser.model().query([]).count()``
+
+        :rtype: Deferred<Number>
+
 Low-level API: RPC calls to Python side
 ---------------------------------------