Creating a custom layout for our form
So far, we have relied on Plone (in fact, plone.app.z3cform) to supply a default template for our forms. This uses the default Plone form markup, which is consistent with that used in other forms in Plone. For many forms, this is all we need. However, it is sometimes useful to create a custom template.
Custom templates are normally needed for one of two reasons: Either, to insert some additional markup around or inside the form itself; or to radically change the form markup itself. The former is more common, since changing the form look-and-feel is normally done better with CSS. For that reason, plone.app.z3cform registers a view called @@ploneform-macros, which provides useful macros for rendering forms using the standard markup. We will illustrate how to use this below.
The easiest way to associate a template with a form is to use the default grokked template association. Our form is called OrderForm and lives a module called order.py, so the grokker will look for a template in order_templates/orderform.pt.
With the exception of DisplayForms, there is always a default template for forms extending the grokked base classes in plone.directives.form. Therefore, the template is optional. Unlike grok.View views, there is no need to override render() if the template is omitted.
As an example, let’s create such a template and add some content before the form tag:
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:metal="http://xml.zope.org/namespaces/metal" xmlns:tal="http://xml.zope.org/namespaces/tal" xmlns:i18n="http://xml.zope.org/namespaces/i18n" i18n:domain="example.dexterityforms" metal:use-macro="context/main_template/macros/master"> <metal:block fill-slot="main"> <h1 class="documentFirstHeading" tal:content="view/label | nothing" /> <p>Welcome to Backgammon Pizza! We hope you enjoy our food.</p> <div id="content-core"> <metal:block use-macro="context/@@ploneform-macros/titlelessform" /> </div> </metal:block> </html>
Notice how the @@ploneform-macros view does most of the work. This contains a number of useful macros:
- form is a full page form, including the label
- titlelessform includes the form status at the top, the <form /> element, and the contents of the fields and actions macros. It also defines three slots: formtop, just inside the <form> opening tag; formbottom, just before the </form> closing tag; and beforeactions, just before the form actions (buttons) are output.
- fields iterates over all widgets in the form and renders each, using the contents of the field macro.
- field renders a single field. It expects the variable widget to be defined in the TAL scope, referring to a z3c.form widget instance. It will output an error message if there is a field validation error, a label, a marker to say whether the field is required, the field description, and the widget itself (normally just an <input /> element).
- actions renders all actions on the form. This normally results in a row of <input type=“submit” … /> elements.
If you require more control, you can always create your form from scratch. Take a look at macros.pt in plone.app.z3cform for inspiration.
If you don’t require tabbed fieldsets or “inline” field validation, the template can be simplified substantially. See macros.pt in plone.z3cform for a cleaner example.
The most important variables used in the template are:
- view.id, a unique id for the form
- view.enctype, the form’s enctype attribute
- view.label, the form’s title
- view.description, the forms’ description
- view.status, a status message that is often set in action handlers.
- view.groups, a list of fieldsets (groups), as represented by Group instances.
- view.widgets, which contains all widgets. view.widgets.errors contains a list of error snippet views. Otherwise, widgets behaves like an ordered dictionary. Iterating over its values() will yield all widgets in order. The widgets have been updated, and can be output using their render() method.
- view.actions, contains an ordered dictionary of actions (buttons). Iterating over its values() will yield all actions in order. The actions have been updated, and can be output using their render() method.