Wagtail 2.15 is designated a Long Term Support (LTS) release. Long Term Support releases will continue to receive maintenance updates as necessary to address security and data-loss related issues, up until the next LTS release (typically a period of 12 months).
* Add the ability for the page chooser to convert external urls that match a page to internal links, see :ref:`WAGTAILADMIN_EXTERNAL_LINK_CONVERSION` (Jacob Topp-Mugglestone. Sponsored by The Motley Fool)
* Added "Extending Wagtail" section to documentation (Matt Westcott)
* Added a `background_position_style` property to renditions. This can be used to crop images using its focal point in the browser. See :ref:`rendition_background_position_style` (Karl Hobley)
* Added ``ExcelDateFormatter`` to ``wagtail.admin.views.mixins`` so that dates in Excel exports will appear in the locale's ``SHORT_DATETIME_FORMAT`` (Andrew Stone)
* Menu sidebar hamburger icon on smaller viewports now correctly indicates it is a button to screen readers and can be accessed via keyboard (Amy Chan, Dan Braghis)
*``blocks.MultipleChoiceBlock``, ``forms.CheckboxSelectMultiple`` and ``ArrayField`` checkboxes will now stack instead of display inline to align with all other checkboxes fields (Seb Brown)
Several Wagtail hooks provide a mechanism for passing Python objects to be rendered as HTML inside admin views, and the APIs for these objects have been updated to adopt a common :doc:`template components </extending/template_components>` pattern. The affected objects are:
* Homepage panels (as registered with the :ref:`construct_homepage_panels` hook)
* Homepage summary items (as registered with the :ref:`construct_homepage_summary_items` hook)
* Page action menu items (as registered with the :ref:`register_page_action_menu_item` and :ref:`construct_page_action_menu` hooks)
* Snippet action menu items (as registered with the :ref:`register_snippet_action_menu_item` and :ref:`construct_snippet_action_menu` hooks)
User code that creates these objects should be updated to follow the component API. This will typically require the following changes:
* Homepage panels should be made subclasses of ``wagtail.admin.ui.components.Component``, and the ``render(self)`` method should be changed to ``render_html(self, parent_context)``. (Alternatively, rather than defining ``render_html``, it may be more convenient to reimplement it with a template, as per :ref:`creating_template_components`.)
* Summary item classes can continue to inherit from ``wagtail.admin.site_summary.SummaryItem`` (which is now a subclass of ``Component``) as before, but:
* Action menu items for pages and snippets can continue to inherit from ``wagtail.admin.action_menu.ActionMenuItem`` and ``wagtail.snippets.action_menu.ActionMenuItem`` respectively - these are now subclasses of ``Component`` - but:
* Any ``template`` attribute should be changed to ``template_name``;
* Any ``get_context`` method should be renamed to ``get_context_data``;
* The ``get_url``, ``is_shown``, ``get_context_data`` and ``render_html`` methods no longer accept a ``request`` parameter. The request object is available in the context dictionary as ``context['request']``.
When defining new action types for :ref:`audit logging <audit_log>` with the :ref:`register_log_actions` hook, it was previously possible to pass a callable as the message. This is now deprecated - to define a message that depends on the log entry's data, you should now create a subclass of ``wagtail.core.log_actions.LogFormatter``. For example:
..code-block:: python
from django.utils.translation import gettext_lazy as _
