[ADD] guide for developing client actions

bzr revid: xmo@openerp.com-20110920095657-9rk9ktekn1uuf36d

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diff --git a/doc/source/addons.rst b/doc/source/addons.rst
index 856c8b2a6c3..3b749ff529c 100644
--- a/doc/source/addons.rst
+++ b/doc/source/addons.rst
@@ -282,6 +282,18 @@ view managers can correctly communicate with them:
     defining e.g. the ``start`` method) or at the instance level (in the
     class's ``init``), though you should generally set it on the class.
 
+Frequent development tasks
+--------------------------
+
+There are a number of tasks which OpenERP Web developers do or will need to
+perform quite regularly. To make these easier, we have written a few guides
+to help you get started:
+
+.. toctree::
+    :maxdepth: 1
+
+    guides/client-action.rst
+
 Utility behaviors
 -----------------
 
diff --git a/doc/source/guides/client-action.rst b/doc/source/guides/client-action.rst
new file mode 100644
index 00000000000..2e1177371a2
--- /dev/null
+++ b/doc/source/guides/client-action.rst
@@ -0,0 +1,92 @@
+Creating a new client action
+============================
+
+Client actions are the client-side of OpenERP's "Server Actions": instead of
+allowing for semi-arbitrary code to be executed in the server, they allow
+for execution of client-customized code.
+
+On the server side, a client action is an action of type ``ir.actions.client``,
+which has (at most) two properties: a mandatory ``tag``, which is an arbitrary
+string by which the client will identify the action, and an optional ``params``
+which is simply a map of keys and values sent to the client as-is (this way,
+client actions can be made generic and reused in multiple contexts).
+
+General Structure
+-----------------
+
+In the OpenERP Web code, a client action only requires two pieces of
+information:
+
+* Mapping the action's ``tag`` to an OpenERP Web object
+
+* The OpenERP Web object itself, which must inherit from
+  :js:class:`openerp.web.Widget`
+
+Our example will be the actual code for the widgets client action (a client
+action displaying a ``res.widget`` object, used in the homepage dashboard of
+the web client):
+
+.. code-block:: javascript
+
+    // Registers the object 'openerp.web_dashboard.Widget' to the client
+    // action tag 'board.home.widgets'
+    openerp.web.client_actions.add(
+        'board.home.widgets', 'openerp.web_dashboard.Widget');
+    // This object inherits from View, but only Widget is required
+    openerp.web_dashboard.Widget = openerp.web.View.extend({
+        template: 'HomeWidget'
+    });
+
+At this point, the generic ``Widget`` lifecycle takes over, the template is
+rendered, inserted in the client DOM, bound on the object's ``$element``
+property and the object is started.
+
+If the client action takes parameters, these parameters are passed in as a
+second positional parameter to the constructor:
+
+.. code-block:: javascript
+
+    init: function (parent, params) {
+        // execute the Widget's init
+        this._super(parent);
+        // board.home.widgets only takes a single param, the identifier of the
+        // res.widget object it should display. Store it for later
+        this.widget_id = params.widget_id;
+    }
+
+More complex initialization (DOM manipulations, RPC requests, ...) should be
+performed in the ``start()`` method.
+
+.. note::
+    As required by ``Widget``'s contract, if ``start`` executes any
+    asynchronous code it should return a ``$.Deferred`` so callers know when
+    it's ready for interaction.
+
+    Although generally speaking client actions are not really interacted with.
+
+.. code-block:: javascript
+
+    start: function () {
+        return $.when(
+            this._super(),
+            // Simply read the res.widget object this action should display
+            new openerp.web.DataSet(this, 'res.widget').read_ids(
+                [this.widget_id], ['title'], this.on_widget_loaded));
+    }
+
+The client action can then behave exactly as it wishes to within its root
+(``this.$element``). In this case, it performs further renderings once its
+widget's content is retrieved:
+
+.. code-block:: javascript
+
+    on_widget_loaded: function (widgets) {
+        var widget = widgets[0];
+        var url = _.sprintf(
+            '/web_dashboard/widgets/content?session_id=%s&widget_id=%d',
+            this.session.session_id, widget.id);
+        this.$element.html(QWeb.render('HomeWidget.content', {
+            widget: widget,
+            url: url
+        }));
+    }