Here's some sci fi I wrote up about a "page" ZCML directive. As Tim Hoffman suggested, maybe the fact that the "page" is passed into the template would give us enough "pull" capability to avoid any of the other hacks I proposed to push global names into every rendered template.
Note that the "view" directive could probably eventually be changed to do everything that the "page" directive I describe below does. Comments appreciated. repoze.bfg.page README ====================== ``repoze.bfg.page`` is a package which adds a ``page`` ZCML directive to the set of directives that may be used under BFG. You might use a ``page`` directive in places where you would otherwise use the built-in repoze.bfg ``view`` directive. Defining a ``page`` directive effectively creates a single BFG view "under the hood", and owns attributes similar to those of a view directive. However, the ``page`` directive differs from the BFG ``view`` directive in a number of important ways: - The ``page`` directive allows you to associate a *template* with the page being defined. The machinery behind the ``page`` directive is capable of rendering an associated template, unlike a view, which must find and render a template itself. - A ``page`` directive, like a BFG ``view`` directive, points at a callable which accepts two arguments: ``context`` and ``request``. This callable must return a Response object *or* a Python dictionary. This is unlike a BFG ``view`` callable, which always returns a Response object (and must never return a dictionary). The ``callable`` which a ``page`` directive points at may optionally be a class. If the page directive's ``callable`` attribute points at a class, that class must have an ``__init__`` method that accepts two arguments: ``context`` and ``request``. That class must further define a ``__call__`` method which accepts no arguments and which returns a dictionary or a Response object. If the page callable returns a Python dictionary, the ``template`` named within the directive will be passed the dictionary as its keyword arguments, and the ``page`` implementation will return the resulting rendered template in a response to the user. The callable object (whatever object was used to define the page ``callable``) will be automatically inserted into the set of keyword arguments passed to the template as ``page``. If the callable object was a class, an instance of that class will be inserted into the keyword arguments as ``page``. If the ``callable`` associated with a ``page`` directive returns a Response object (an object with the attributes ``status``, ``headerlist`` and ``app_iter``), any template associated with the ``page`` declaration is ignored, and the response is passed back to BFG. For example, if your page callable returns an ``HTTPFound`` response, no template rendering will be performed:: from webob.exc import HTTPFound return HTTPFound(location='http://example.com') # templating avoided Here's an example of a page directive which acts as a default view:: <page template="templates/my_template.pt" callable=".pages.my_page" /> The ``template`` attribute is optional. If one is not named, and the callable returns a dictionary, an error will be thrown at rendering time. Special ZCML Attributes ----------------------- The directive accepts attributes other than ``template`` and ``callable``. attr ``repoze.bfg.page`` defaults to using the ``__call__`` method of the page callable to obtain a response dictionary. The ``attr`` value allows you to vary that method name. For example, if your class had a method named ``index`` and you wanted to use this method instead of ``__call__``, you'd say ``attr="index"`` in the page ZCML definition. This is most useful when the page definition is a class. for A Python dotted-path name representing the Python class that the :term:`context` must be an instance of, *or* the :term:`interface` that the :term:`context` must provide in order for this view to be found and called. name The *view name*. Read and understand :ref:`traversal_chapter` to understand the concept of a view name. permission The name of a *permission* that the user must possess in order to call the view. See :ref:`view_security_section` for more information about view security and permissions. request_method This value can either be one of the strings 'GET', 'POST', 'PUT', 'DELETE', or 'HEAD' representing an HTTP ``REQUEST_METHOD``. A view declaration with this attribute ensures that the view will only be called when the request's ``method`` (aka ``REQUEST_METHOD``) string matches the supplied value. request_param This value can be any string. A view declaration with this attribute ensures that the view will only be called when the request has a key in the ``request.params`` dictionary (an HTTP ``GET`` or ``POST`` variable) that has a name which matches the supplied value. If the value supplied to the attribute has a ``=`` sign in it, e.g. ``request_params="foo=123"``, then the key (``foo``) must both exist in the ``request.params`` dictionary, and the value must match the right hand side of the expression (``123``) for the view to "match" the current request. containment This value should be a Python dotted-path string representing the class that a graph traversal parent object of the :term:`context` must be an instance of (or :term:`interface` that a parent object must provide) in order for this view to be found and called. Your models must be "location-aware" to use this feature. See :ref:`location_aware` for more information about location-awareness. route_name *This attribute services an advanced feature that isn't often used unless you want to perform traversal *after* a route has matched.* This value must match the ``name`` of a ``<route>`` declaration (see :ref:`urldispatch_chapter`) that must match before this view will be called. The ``<route>`` declaration specified by ``route_name`` must exist in ZCML before the view that names the route (XML-ordering-wise) . Note that the ``<route>`` declaration referred to by ``route_name`` usually has a ``*traverse`` token in the value of its ``path`` attribute, representing a part of the path that will be used by traversal against the result of the route's :term:`root factory`. See :ref:`hybrid_chapter` for more information on using this advanced feature. request_type This value should be a Python dotted-path string representing the :term:`interface` that the :term:`request` must have in order for this view to be found and called. See :ref:`view_request_types_section` for more information about request types. For backwards compatibility with :mod:`repoze.bfg` version 1.0, this value may also be an HTTP ``REQUEST_METHOD`` string, e.g. ('GET', 'HEAD', 'PUT', 'POST', or 'DELETE'). Passing request method strings as a ``request_type`` is deprecated. Use the ``request_method`` attribute instead for maximum forward compatibility. Special Keyword Names When A Callable Returns A Dictionary ---------------------------------------------------------- Several keyword names in a dictionary return value of a page callable are treated specially by the page implementation. These values are passed through to the template during rendering, but they also influence the response returned to the user separate from any template rendering. Page callables should set these values into the dictionary they return to influence response attributes. content_type Defines the content-type of the resulting response, e.g. ``text/xml``. headerlist A sequence of tuples describing cookie values that should be set in the response, e.g. ``[('Set-Cookie', 'abc=123'), ('X-My-Header', 'foo')]``. status A WSGI-style status code (e.g. ``200 OK``) describing the status of the response. charset The character set (e.g. ``UTF-8``) of the response. cache_for A value in seconds which will influence ``Cache-Control`` and ``Expires`` headers in the returned response. The same can also be achieved by returning various values in the headerlist, this is purely a convenience. Default Template Filename Extension Mappings -------------------------------------------- A file extension mapping is used to determine which templating system renderer to use to render any given template. By default, a single filename-extension-to-renderer mapping is used: any template name with a filename extension of ".pt" is assumed to be rendered via a Chameleon ZPT template. By default, if a template renderer cannot be recognized by its extension, it will be assumed that a Chameleon text renderer should be used to render the template. Adding and Overriding Template Filename Extension Mappings ---------------------------------------------------------- Additonal declarations can be made which override a default file-extension-to-renderer mapping or add a new file-extension-to-renderer mapping. This is accomplished via one or more separate ZCML directives. For example, to add Jinja2 rendering (after installing the repoze.bfg.jinja2" package), whereby filenames that end in ``.jinja`` are rendered by the Jinja2 renderer:: <utility provides="repoze.bfg.page.IPageRenderer" name=".jinja" component="repoze.bfg.jinja2.render_template_to_response"/> To override the default mapping in which files with a ``.pt`` extension are rendered via a Chameleon ZPT page template renderer, use a variation on the following:: <utility provides="repoze.bfg.page.IPageRenderer" name=".pt" component="my.package.pt_renderer"/> By default, when a template extension is unrecognized, the Chameleon text templating engine is assumed. You can override the default renderer by creating an ``IPageRenderer`` utility which has no ``name``:: <utility provides="repoze.bfg.page.IPageRenderer" component="my.package.default_renderer"/> The ``component`` named within any of these directives must be a callable which accepts the following arguments: ``(template_name, request, **kw)``. It must return a Response object. _______________________________________________ Repoze-dev mailing list Repoze-dev@lists.repoze.org http://lists.repoze.org/listinfo/repoze-dev