Field formatters are responsible for taking the data stored by a field and transforming it into what a visitor sees. We can define new field formatters to output data for new field types or to provide alternative formatting options for existing field types. Creating a field formatter plugin is a common task for Drupal developers.

In this tutorial we'll:

• Define a new background color field formatter that uses the string stored by our field_example_rgb field type as the background color of the output.
• Make it possible for site builders to toggle on or off a feature that automatically adjusts the foreground text color of the output.

By the end of this tutorial you should be able to define a new custom field formatter plugin with settings that a site administrator can configure.

If you've ever created or edited a piece of content on a Drupal site you have already interacted with the Field API. The Field module (along with its user interface counterpart) is responsible for providing the forms and data components used to build up the content model that make up a Drupal site. Understanding how Drupal fields work and how they're constructed via the Field API is an important part of understanding how Drupal works.

In this tutorial, we're going to look at the main components that make up the Field API at a high level. We'll see how the Field UI module exposes the field types included in core. We'll also look at the three main pieces that compose fields: types, widgets and formatters.

Drupal's Field API specifies the implementation details for field types, widgets and formatters. It also provides several hooks that allow custom code to alter these implementation details. In this tutorial we'll take a look at these Field API hooks and see how they can be used to change field types, widgets and formatters.

By the end of this lesson, you should be able to:

• Identify existing Field API hooks for manipulating field behavior
• Understand the proper method for changing the behavior of a field type, widget or formatter
• Know where to find the documentation for these API functions, and how to find their implementations

Of the 3 main components of the field system -- types, widgets and formatters -- only 1 has an impact on the actual display of content for end users: field formatters. Field formatters are responsible for taking the data stored by a field and transforming it into the markup that is sent to the browser when an end user views your site.

In this tutorial we'll:

• Look at the role field formatters play in the Field API
• Identify the main components that make up a field formatter

By the end of this tutorial you should be able to define the role of a field formatter plugin.

Drupal's field system provides us with a flexible system of adding different types of discrete data to content types. This enables us to create rich content models. The Field API allows us to define these distinct field types by creating a new plugin. These plugins specify a FieldType attribute. In this tutorial, we'll look at these attributes in detail. We'll look at the implementations of field types from Drupal core. Also, we'll see what a new custom field type would look like.

By the end of this tutorial, you should be able to:

• Understand how field type definitions are created and exposed to Drupal
• Identify the various field types provided by Drupal core
• Understand the requirements for providing a specification for a new field type

Once we've explored the various field types provided by Drupal core, the next component of the Field API to explore is field widgets. Field widgets define how the data structure of the field is displayed on an edit form. When content editors interact with your field type they will be doing so via the field widget you provide. In this tutorial, we'll take a look at the field widgets provided by Drupal core, the plugin type required to define our own custom widget and how we can define multiple widget options for a single field type.

By the end of this tutorial, you should be able to:

• Understand where field widgets fit into the overall Field API
• Implement a custom field widget to support a particular field type

Set up a local development environment to practice Drupal theme development exercises in our course, Hands-On Theming Exercises for Drupal.

By the end of this tutorial, you should be able to:

• Install Drupal on your computer, so you can edit files in your theme.
• Generate dummy content, so that you have different kinds of pages to theme.

It's time to create the bare-bones structure for a new theme on your site. You should try to complete this exercise based what you've learned from the tutorial prerequisites listed below. The video at the end of this tutorial will walk you through the implementation of this exercise if you need some help. In this exercise, we'll:

• Create an info file that describes a custom theme to Drupal with the regions listed below (we're going to name ours "reboot").
• Enable, and view, a bare-bones custom theme.

By the end of this exercise, you should feel comfortable starting a theme using several methods.

To add CSS or JavaScript files or libraries to your site, you can attach them as asset libraries in your theme. In this exercise, you'll create 2 asset libraries and attach them globally via your theme's info file. In this tutorial, we'll pull in the CSS and JavaScript from the popular Bootstrap framework so that we can make use of its layout utility classes later on. We'll also add a custom CSS file that contains global styles for our site, like setting the page background color.

If you want to try and complete this on your own first you'll need to:

• Add the Bootstrap CSS and JavaScript files to your theme.
• Define an asset library using a THEMENAME.libraries.yml file in your theme.
• Tell Drupal to attach your asset library so that the CSS and JavaScript files it represents are included in the page.

Once that's done your site won't look all that different. But if you view the page source, or look closely, you should see that the Bootstrap files are included along with any CSS rules you placed into your custom style sheet.

Note: Since this course is focused on teaching the Drupal aspects of theme development, and not on writing CSS, we're using the Bootstrap CSS. Feel free to use the framework or library of your choice if you don't want to use Bootstrap.

You should try to complete the exercise steps on your own and use the video to help guide you if you get stuck.

At the end of this exercise, you'll find a video walk-through of the solution.

Drupal has a few handy settings you can tweak to make developing themes a little more intuitive and a lot more awesome. In this tutorial, we'll practice manually setting up our environment for theme development by:

• Disabling some caches
• Turning off CSS and JS aggregation
• Turning on the Twig debug service

By the end of this tutorial, you'll have practiced setting up your environment for theme development.

In order to change Drupal's default markup you need to override template files. The page template controls the overall layout of your theme, including the placement of regions. You should practice the exercise following the written instructions below. Use the video walk-through to help if you get stuck.

In this exercise, we'll:

• Override the currently used page.html.twig template file.
• Modify the content of the file to include the regions defined in the theme's .info.yml file.
• Wrap the regions in the page template file with HTML markup using CSS classes from Bootstrap to achieve the example layout.

By the end of this tutorial, you'll gain practice creating a custom layout in a page template file.

The available dynamic tokens or variables vary from template to template. Each page is built from a set of templates.

In this exercise, we'll:

• Override and name the node template file so that it will only affect Article nodes on our Drupal site.
• Inspect the available variables.
• Customize the markup.
• Use the Twig filter without.

We recommend that you try to work through the exercise yourself, and refer to the video if you need help.

In this exercise, we'll practice theming by overriding the main menu template. We'll:

• Override and rename the main menu template so that it will only affect the main menu component of our Drupal site.
• Add Bootstrap classes from the base nav component into our overridden main menu template file.
• Add CSS classes to HTML selectors using attributes.addClass() and set methods.

We recommend that you work on the exercise steps below first. You can refer to the video if you need some help.

In this exercise, we'll continue our template overriding practice by overriding the image field template. We'll consult the Bootstrap documentation and add a responsive image class that will apply to any images uploaded by a user to the field_image field. Once again, we'll add this class to the classes array in the set Twig tag. You should work on the exercise steps below first, and you can refer to the video if you need some help.

In this exercise, we'll practice using the t filter in a Twig template. As a best practice, all hard-coded text in a template should be translatable. Simple text (containing no dynamic tokens) can be passed through the t filter to achieve this objective. Along the way, we'll also use a basic conditional if statement with Twig. We recommend that you try following the exercise's steps first, and refer to the video if you need help.

Preprocess functions allow you to change existing variables, or add new variables, for a template file using PHP code. In this exercise, you'll:

• Define a PHP function that implements a preprocess hook
• Create a new variable named {{ today }} that contains the current date and gets passed to the page.html.twig template file.

We recommend that you try the exercise's steps first, and refer to the video if you need help.

Layout Builder is one of many different approaches to handling editorial layouts in Drupal. Now that it's stable, and part of Drupal core, we expect to see it become the dominant approach over time. However, as with most things in Drupal, there are multiple ways to solve the problem of creating component based flexible layouts that can be administered via the user interface.

It's a good idea to understand the different approaches and know what's available.

When it comes to component based design and ability to construct flexible layouts, it is important to understand the benefits and risks of the most popular techniques: Paragraphs, Bricks, entities and view modes, and Layout Builder. Understanding which approach fits the needs of your project best can be critical for its success in the future.

In this tutorial we'll look at some common approaches to administering layouts in a way that gives content editors controls including:

• Drupal core's Layout Builder
• Using core's entity reference fields and view modes
• The contributed Paragraphs module
• The contributed Bricks module

By the end of this tutorial you should have a broad overview of the different popular approaches to creating editor-controlled layouts.

In their simplest form layout plugins in Drupal Layout Builder define the part of the content output that can't be changed. For example a three column layout will consist of three equal columns every time an editor decides to use it as the layout section. The editor can place whatever they want into the three columns. But they can not change the overall layout. This restricts editorial capabilities of using layout plugins since in real life a three column layout may need to consist of a wider middle column and narrower side columns, allow for column headings, or other customizations.

This flexibility is accomplished by creating, and exposing, configuration options for layout plugins in Drupal's Layout Builder. In more advanced cases, we can take this flexibility further by exposing an interface editors to dynamically define layout plugins.

In this tutorial we'll:

• Learn how to use custom PHP classes in the layout plugin annotation
• Learn what annotations properties can be used for custom layout declaration
• Define the concept of derivatives and outline scenarios for using them
• How to declare static single layouts using YAML format

By the end of this tutorial you'll learn advanced ways of declaring configurable custom layout plugins.

A new favorite page-building and design module in Drupal's core software, Layout Builder makes it possible to create content-type-specific layouts. All nodes of the associated content type will display their content using the defined layout. This allows site builders to display a page's content in two columns, or three, or two columns with a full-width banner image, etc. Then you can place the content type's fields and Drupal blocks into the sections of the defined layout, all via the Drupal UI.

In this tutorial we'll:

• Enable the Drupal Layout Builder and Layout Discover modules
• Create a new two-column flexible layout via the user interface
• Update the Basic page content type so that all nodes use the new two-column layout

By the end of this tutorial you should know how to create a new flexible layout, and apply it to one or more content types.

When building with Layout Builder, the list of blocks available for a site administrator to place in a layout can grow and become overwhelming to navigate. This is especially true when you've got a lot of different modules enabled, as each can add new blocks. As well, complex configurations may require site admins to create more and more custom blocks. Some blocks, like certain Views, or default core blocks like "Who's online", are not meant to be used within the Layout Builder. These blocks can clutter the UI and also impact the performance of Layout Builder UI. The contributed module Block List Override is designed to help solve this problem.

In this tutorial we'll:

• Learn what the Block List Override module does
• Install and configure the module to improve the user experience when creating layouts

By the end of this tutorial you should know how to use the Block List Override module to improve the UX of the Layout Builder interface.