A request instance is created when an HTTP request is sent to the web

server.  It contains informations such as form parameters,

authenticated user, etc. It is a very prevalent object and is used

throughout all of the framework and applications.

**A request represents a user query, either through HTTP or not (we

also talk about RQL queries on the server side for example).**

Here is a non-exhaustive list of attributes and methods available on

request objects (grouped by category):

* `Browser control`:

  * `ie_browser`: tells if the browser belong to the Internet Explorer

    family

  * `xhtml_browser`: tells if the browser is able to properly handle

    XHTML (at the HTTP content_type level)

* `User and identification`:

  * `user`, instance of `cubicweb.common.utils.User` corresponding to

    the authenticated user

* `Edition` (utilities for edition control):

  * `cancel_edition`: resets error url and cleans up pending operations

  * `create_entity`: utility to create an entity (from an etype,

    attributes and relation values)

  * `datadir_url`: returns the url to the merged external resources

    (|cubicweb|'s `web/data` directory plus all `data` directories of

    used cubes)

  * `edited_eids`: returns the list of eids of entities that are

    edited under the current http request

  * `eid_rset(eid)`: utility which returns a result set from an eid

  * `entity_from_eid(eid)`: returns an entity instance from the given eid

  * `encoding`: returns the encoding of the current HTTP request

  * `ensure_ro_rql(rql)`: ensure some rql query is a data request

  * etype_rset

  * `form`, dictionary containing the values of a web form

  * `encoding`, character encoding to use in the response

  * `next_tabindex()`: returns a monotonically growing integer used to

    build the html tab index of forms

* `HTTP`

  * `authmode`: returns a string describing the authentication mode

    (http, cookie, ...)

  * `lang`: returns the user agents/browser's language as carried by

    the http request

  * `demote_to_html()`: in the context of an XHTML compliant browser,

    this will force emission of the response as an HTML document

    (using the http content negociation)

  * `build_url(__vid, *args, **kwargs)`: return an absolute URL using

    params dictionary key/values as URL parameters. Values are

    automatically URL quoted, and the publishing method to use may be

    specified or will be guessed.

  * `build_url_params(**kwargs)`: returns a properly prepared (quoted,

    separators, ...) string from the given parameters

* `Web resource (.css, .js files, etc.) handling`:

  * `add_css(cssfiles)`: adds the given list of css resources to the current

    html headers

  * `add_js(jsfiles)`: adds the given list of javascript resources to the

    current html headers

  * `add_onload(jscode)`: inject the given jscode fragment (an unicode

    string) into the current html headers, wrapped inside a

    document.ready(...) or another ajax-friendly one-time trigger event

  * `add_header(header, values)`: adds the header/value pair to the

    current html headers