..  include:: /Includes.rst.txt

..  _introduction:

============
Introduction
============

What does it do?
================

The :guilabel:`Frontend Theme for Extension Development` extension provides a
TYPO3 frontend theme for development purposes. Its job is to give a TYPO3
installation a reasonable frontend to look at and to render against, without
building a site package for it first.

..  important::

    The theme is not finished. What this chapter describes is what the extension
    is for; see the note at the end of this section for what it already does.

The situations it is built for, where an extension has to be seen or exercised
in a frontend rather than only in a test assertion:

*   **Extension development**, to click through what an extension actually
    outputs instead of reading the rendered HTML in a test failure.
*   **DDEV based test instances** of an extension repository, where a throwaway
    TYPO3 installation needs a frontend rendering pages, navigation and
    content elements.
*   **Acceptance tests**, which need a stable and predictable frontend to
    drive a browser against.
*   **Reproducing an issue** in a minimal installation before debugging it.

..  warning::

    This is a development tool, not a production theme. It is meant to be
    required as a development dependency of an extension repository or
    installed into a disposable test instance, and it makes no promise about
    design, markup stability or upgrade paths for a live site.

..  note::

    The theme renders a page once a site depends on its site set — see
    :ref:`configuration`. It covers **every classic content element**
    :file:`EXT:frontend` registers, the eleven menu elements, ten elements of
    its own, and third-party Extbase plugins, none of which requires
    :file:`fluid_styled_content` — that extension is not a dependency here, and
    on TYPO3 v14 it is not installed at all. It ships five backend layouts, a
    main menu, a section menu and a breadcrumb, and a light/dark appearance
    switch. A seeded ``/styleguide`` page renders the whole component library
    on one page, so the theme can be looked at without building content for it
    first — see :ref:`feature-styleguide`. This chapter is extended along with
    the implemented features.

    Underneath that sits the foundation: TYPO3 v13 and v14 support from one code
    base with :ref:`core version aware <introduction-core-version-aware>`
    classes, wired by the dependency injection container of the running TYPO3
    version.

..  _introduction-core-version-aware:

Core version aware implementations
==================================

Code that has to differ between the supported TYPO3 versions lives below
:file:`Core13/` and :file:`Core14/` in the repository root. Shared code —
interfaces, abstract base classes and everything working on both core
versions — lives in :file:`Classes/`.

Only the directory matching the running TYPO3 version is registered in the
dependency injection container, so a service asking for an interface always
receives the implementation matching the current core version.

Compatibility
=============

..  list-table::
    :header-rows: 1

    *   -   Branch
        -   Extension
        -   TYPO3
        -   PHP
    *   -   main
        -   2.x
        -   v13.4 / v14.3
        -   8.2 - 8.5
    *   -   1
        -   1.x
        -   v12.4 / v13.4
        -   8.1 - 8.4

This manual documents the ``main`` branch. Branch ``1`` is the maintained line
for the previous core version tuple and has a manual of its own; PHP 8.1 is
supported there for TYPO3 v12 only, because TYPO3 v13.4 requires PHP 8.2.

Contributing
============

Contributions are welcome. The development setup, the quality gates and the
commit message rules are described in the :file:`CONTRIBUTING.md` file of the
`source repository <https://github.com/sbuerk/theme-extension-development>`__.