Preview: form page

Copy this page: app/form.html
brickwork ships whole pages as examples you own outright, not as templates you extend. Copy this into your own project and edit it.
{% extends "brickwork/shell/app.html" %}
{% comment %}
A create/edit page: one form on a page.

COPY THIS FILE into your project and edit it. It is not on the template loader
path, so you cannot extend it (ADR-056).

Beat Phase D journey: Form validate (icvoss/django-brickwork#544). This file
IS the shared partial plus the 422 path: `{% partialdef form_region inline %}`
keeps the full-page render and the HTMX invalid re-render on one block.
Wire the view branches in docs/INTEGRATION.md section 4 (no-JS 200 full page,
HTMX 422 + `#form_region`, success HX-Redirect). Do not invent a second form
template.

What your view must supply:
    form         your own Django form (bound on POST)
    nav_items / nav_active  as in list.html

THE ONE RULE HERE: you own the <form> element, brickwork never emits it.
That is not a limitation, it is the only sound arrangement: only your project
knows its own action URL, and a template that wrapped your fields in its own
<form> would put your submit button outside it. So the <form>, the csrf_token,
and the submit all live together in this file, which you own.

States: valid/invalid per field (bw_form renders the bound form's own
  errors inline); the 422 HTMX re-render path swaps this same region with
  inline errors, never a full page reload, when wired.
Accessibility: inherits shell/app.html's skip link, sidebar/drawer nav and
  page-header region; every field renders through the standard
  forms/_field.html chrome (label/aria-describedby/error wiring); the
  cancel link is a real anchor, never a button pretending to navigate.
  Covered by the archetype harness's full gate sweep (render, axe WCAG 2.2
  AA, no horizontal overflow, light/dark distinctness, skip-link
  first-tab-stop with JS disabled) at every W0.1 breakpoint, both themes;
  the underlying bw_form grid layout and its error states are additionally
  covered by axe.spec.mjs against form-*.html/form-errors-*.html (axe on
  the invalid state is the journey floor; keep that fixture green).
Responsive: no breakpoint switch of its own; inherits shell/app.html's
  sidebar-to-drawer collapse at --bw-breakpoint-md (48rem). bw_form's own
  grid layout (when grid_columns is set) collapses to one column below
  --bw-breakpoint-sm (40rem), per that tag's own documentation.
{% endcomment %}
{% load brickwork_components brickwork_forms brickwork_nav %}

{% block page_title %}New invoice - Northwind{% endblock %}

{% block sidebar %}{% bw_nav nav_items nav_active %}{% endblock %}
{% block sidebar_mobile %}{% bw_nav nav_items nav_active %}{% endblock %}
{% block brand_wordmark %}Northwind{% endblock %}

{% block page_header %}
  {% include "brickwork/components/_page_header.html" with title="New invoice" description="Raise an invoice against one of your accounts." %}
{% endblock %}

{% block content %}
<div class="bw-section-stack">

  {% comment %}
  Point the action at your own URL. {{ request.path }} posts back to this same
  page, which is the usual shape for a create/edit view: on success the view
  redirects, on failure it re-renders this page with the bound, invalid form
  and the errors appear inline automatically.

  bw_form renders form.visible_fields() generically, so it works with any
  form: ModelForm, plain Form, allauth's, your own. It also includes the
  non-field error region itself, so never include _form_errors.html a second
  time beside it.

  The hx-* attributes are progressive enhancement: without htmx the form is a
  plain POST and the no-JS floor still works (BR-BW-HTMX-001). With htmx, an
  invalid response must be 422 targeting this same region (see INTEGRATION.md).
  {% endcomment %}
  {% partialdef form_region inline %}
  <form id="invoice-form" method="post" action="{{ request.path }}"
        hx-post="{{ request.path }}"
        hx-target="this"
        hx-swap="outerHTML">
    {% csrf_token %}
    {% comment %}
    Stacked fields with the amount control wrapped in input_group for a
    currency prefix (icvoss/django-brickwork#624). Other fields use the
    ordinary _field.html chrome; non-field errors stay above the stack.
    {% endcomment %}
    {% include "brickwork/forms/_form_errors.html" with form=form %}
    <div class="bw-form-fields bw-form-fields--stacked">
      {% for field in form.visible_fields %}
        <div class="bw-field-row">
          {% if field.name == "amount" %}
            {% with errors=field.errors help_id=field.auto_id|add:"_help" error_id=field.auto_id|add:"_errors" %}
            <div class="bw-field{% if errors %} bw-field--invalid{% endif %}">
              <label class="bw-field__label" {% bw_attr "for" field.id_for_label %}>
                {{ field.label }}{% if field.field.required %} <span class="bw-field__required" aria-hidden="true">*</span>{% endif %}
              </label>
              <div class="bw-field__control">
                {% bw_field_widget field as amount_widget %}
                {% include "brickwork/components/_input_group.html" with prefix="£" field=amount_widget %}
              </div>
              {% if field.help_text %}
                <p class="bw-field__help" id="{{ help_id }}">{{ field.help_text }}</p>
              {% endif %}
              <div class="bw-field__errors" id="{{ error_id }}" role="alert">
                {% for error in errors %}
                  <p class="bw-field__error">{{ error }}</p>
                {% endfor %}
              </div>
            </div>
            {% endwith %}
          {% else %}
            {% include "brickwork/forms/_field.html" with field=field %}
          {% endif %}
        </div>
      {% endfor %}
    </div>
    {% for hidden in form.hidden_fields %}{{ hidden }}{% endfor %}

    {% comment %}
    The submit sits INSIDE the form, beside the fields. A cancel link beside
    it is an ordinary anchor, not a button: it navigates, it does not submit.
    {% endcomment %}
    <div class="bw-form__actions">
      {% bw_button "Save invoice" type="submit" variant="primary" %}
      {% bw_button "Cancel" variant="ghost" href="/invoices/" %}
    </div>
  </form>
  {% endpartialdef %}

</div>
{% endblock %}