diff -r 76ab3c71aff2 -r c67bcee93248 doc/book/devweb/js.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/doc/book/devweb/js.rst Thu Jan 08 22:11:06 2015 +0100 @@ -0,0 +1,394 @@ +.. -*- coding: utf-8 -*- + +Javascript +---------- + +*CubicWeb* uses quite a bit of javascript in its user interface and +ships with jquery (1.3.x) and parts of the jquery UI library, plus a +number of homegrown files and also other third party libraries. + +All javascript files are stored in cubicweb/web/data/. There are +around thirty js files there. In a cube it goes to data/. + +Obviously one does not want javascript pieces to be loaded all at +once, hence the framework provides a number of mechanisms and +conventions to deal with javascript resources. + +Conventions +~~~~~~~~~~~ + +It is good practice to name cube specific js files after the name of +the cube, like this : 'cube.mycube.js', so as to avoid name clashes. + +.. XXX external_resources variable (which needs love) + +Server-side Javascript API +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Javascript resources are typically loaded on demand, from views. The +request object (available as self._cw from most application objects, +for instance views and entities objects) has a few methods to do that: + +* `add_js(self, jsfiles, localfile=True)` which takes a sequence of + javascript files and writes proper entries into the HTML header + section. The localfile parameter allows to declare resources which + are not from web/data (for instance, residing on a content delivery + network). + +* `add_onload(self, jscode)` which adds one raw javascript code + snippet inline in the html headers. This is quite useful for setting + up early jQuery(document).ready(...) initialisations. + +Javascript events +~~~~~~~~~~~~~~~~~ + +* ``server-response``: this event is triggered on HTTP responses (both + standard and ajax). The two following extra parameters are passed + to callbacks : + + - ``ajax``: a boolean that says if the reponse was issued by an + ajax request + + - ``node``: the DOM node returned by the server in case of an + ajax request, otherwise the document itself for standard HTTP + requests. + +Important javascript AJAX APIS +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +* `asyncRemoteExec` and `remoteExec` are the base building blocks for + doing arbitrary async (resp. sync) communications with the server + +* `reloadComponent` is a convenience function to replace a DOM node + with server supplied content coming from a specific registry (this + is quite handy to refresh the content of some boxes for instances) + +* `jQuery.fn.loadxhtml` is an important extension to jQuery which + allows proper loading and in-place DOM update of xhtml views. It is + suitably augmented to trigger necessary events, and process CubicWeb + specific elements such as the facet system, fckeditor, etc. + + +A simple example with asyncRemoteExec +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +On the python side, we have to define an +:class:`cubicweb.web.views.ajaxcontroller.AjaxFunction` object. The +simplest way to do that is to use the +:func:`cubicweb.web.views.ajaxcontroller.ajaxfunc` decorator (for more +details on this, refer to :ref:`ajax`). + +.. sourcecode: python + + from cubicweb.web.views.ajaxcontroller import ajaxfunc + + # serialize output to json to get it back easily on the javascript side + @ajaxfunc(output_type='json') + def js_say_hello(self, name): + return u'hello %s' % name + +On the javascript side, we do the asynchronous call. Notice how it +creates a `deferred` object. Proper treatment of the return value or +error handling has to be done through the addCallback and addErrback +methods. + +.. sourcecode: javascript + + function asyncHello(name) { + var deferred = asyncRemoteExec('say_hello', name); + deferred.addCallback(function (response) { + alert(response); + }); + deferred.addErrback(function (error) { + alert('something fishy happened'); + }); + } + + function syncHello(name) { + alert( remoteExec('say_hello', name) ); + } + +Anatomy of a reloadComponent call +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +`reloadComponent` allows to dynamically replace some DOM node with new +elements. It has the following signature: + +* `compid` (mandatory) is the name of the component to be reloaded + +* `rql` (optional) will be used to generate a result set given as + argument to the selected component + +* `registry` (optional) defaults to 'components' but can be any other + valid registry name + +* `nodeid` (optional) defaults to compid + 'Component' but can be any + explicitly specified DOM node id + +* `extraargs` (optional) should be a dictionary of values that will be + given to the cell_call method of the component + +A simple reloadComponent example +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The server side implementation of `reloadComponent` is the +:func:`cubicweb.web.views.ajaxcontroller.component` *AjaxFunction* appobject. + +The following function implements a two-steps method to delete a +standard bookmark and refresh the UI, while keeping the UI responsive. + +.. sourcecode:: javascript + + function removeBookmark(beid) { + d = asyncRemoteExec('delete_bookmark', beid); + d.addCallback(function(boxcontent) { + reloadComponent('bookmarks_box', '', 'boxes', 'bookmarks_box'); + document.location.hash = '#header'; + updateMessage(_("bookmark has been removed")); + }); + } + +`reloadComponent` is called with the id of the bookmark box as +argument, no rql expression (because the bookmarks display is actually +independant of any dataset context), a reference to the 'boxes' +registry (which hosts all left, right and contextual boxes) and +finally an explicit 'bookmarks_box' nodeid argument that stipulates +the target DOM node. + +Anatomy of a loadxhtml call +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +`jQuery.fn.loadxhtml` is an important extension to jQuery which allows +proper loading and in-place DOM update of xhtml views. The existing +`jQuery.load`_ function does not handle xhtml, hence the addition. The +API of loadxhtml is roughly similar to that of `jQuery.load`_. + +.. _`jQuery.load`: http://api.jquery.com/load/ + + +* `url` (mandatory) should be a complete url (typically referencing + the :class:`cubicweb.web.views.ajaxcontroller.AjaxController`, + but this is not strictly mandatory) + +* `data` (optional) is a dictionary of values given to the + controller specified through an `url` argument; some keys may have a + special meaning depending on the choosen controller (such as `fname` + for the JSonController); the `callback` key, if present, must refer + to a function to be called at the end of loadxhtml (more on this + below) + +* `reqtype` (optional) specifies the request method to be used (get or + post); if the argument is 'post', then the post method is used, + otherwise the get method is used + +* `mode` (optional) is one of `replace` (the default) which means the + loaded node will replace the current node content, `swap` to replace + the current node with the loaded node, and `append` which will + append the loaded node to the current node content + +About the `callback` option: + +* it is called with two parameters: the current node, and a list + containing the loaded (and post-processed node) + +* whenever it returns another function, this function is called in + turn with the same parameters as above + +This mechanism allows callback chaining. + + +A simple example with loadxhtml +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Here we are concerned with the retrieval of a specific view to be +injected in the live DOM. The view will be of course selected +server-side using an entity eid provided by the client side. + +.. sourcecode:: python + + from cubicweb.web.views.ajaxcontroller import ajaxfunc + + @ajaxfunc(output_type='xhtml') + def frob_status(self, eid, frobname): + entity = self._cw.entity_from_eid(eid) + return entity.view('frob', name=frobname) + +.. sourcecode:: javascript + + function updateSomeDiv(divid, eid, frobname) { + var params = {fname:'frob_status', eid: eid, frobname:frobname}; + jQuery('#'+divid).loadxhtml(JSON_BASE_URL, params, 'post'); + } + +In this example, the url argument is the base json url of a cube +instance (it should contain something like +`http://myinstance/ajax?`). The actual AjaxController method name is +encoded in the `params` dictionary using the `fname` key. + +A more real-life example +~~~~~~~~~~~~~~~~~~~~~~~~ + +A frequent need of Web 2 applications is the delayed (or demand +driven) loading of pieces of the DOM. This is typically achieved using +some preparation of the initial DOM nodes, jQuery event handling and +proper use of loadxhtml. + +We present here a skeletal version of the mecanism used in CubicWeb +and available in web/views/tabs.py, in the `LazyViewMixin` class. + +.. sourcecode:: python + + def lazyview(self, vid, rql=None): + """ a lazy version of wview """ + w = self.w + self._cw.add_js('cubicweb.lazy.js') + urlparams = {'vid' : vid, 'fname' : 'view'} + if rql is not None: + urlparams['rql'] = rql + w(u'