Drupal comes with all of its caching features enabled by default. This improves response time, but can be frustrating for themers as it makes it harder to preview the changes you make to template files.
In this tutorial we'll look at:
- Why these features are enabled by default
- How the theme layer leverages Drupal's caches
- Why you should learn to disable them when doing development
This tutorial demonstrates how to locate the template file that is currently being used to render an element and override it in your own theme. This is an important skill for anyone who wants to make changes to Drupal's default HTML markup.
In this tutorial we'll:
- Override the node.html.twig template in our theme
- Make changes to the markup
- Create a content-type-specific template override like node--CONTENT_TYPE.html.twig
By the end of this tutorial you should be able to modify the HTML markup used to display a node, or any other element of the page generated using a template file.
Concept: Render API
FreeDrupal's Render API plays a crucial role in how content is presented on a site. The Render API manages how content is rendered through render arrays and render elements.
In this tutorial, we'll:
- Define render arrays, highlighting properties and elements.
- Explain how render elements are used as shorthand for complex structures.
- Describe the primary types of data we can use in a render array.
- Touch on the role of renderers and special methods for rendering entities.
By the end of this tutorial, you'll better understand how Drupal constructs a page's output through render arrays and streamlines rendering with render elements.
Props and slots are the two ways that data can be provided to a single directory component (SDC). They are part of a component's schema definition, and are used to determine the names of variables passed to a component's template file. Props pass structured, validated data into a component, while slots allow us to inject flexible content such as HTML or nested components. Understanding when and how to use each ensures you can build reusable and adaptable components.
In this tutorial, we'll:
- Learn what props and slots are, and how they differ.
- Discuss how using one or the other impacts the developer experience and use of your components in a UI.
- Practice deciding when to use each for component design.
By the end of this tutorial, you'll know how to choose between props and slots when building components.
As we learned in the What Is a Breakpoints YAML file? tutorial, modules and themes can expose their site's CSS breakpoints and media queries to other Drupal modules and themes by implementing a breakpoints YAML file. In that tutorial, you also learned about the structure of a breakpoints configuration file and why you'd want to create one. In this tutorial, we’ll walk through the process of creating an example breakpoints file step-by-step.
By the end of this lesson, you should be able to create a working breakpoints YAML file in a theme or module. We'll test it out by enabling Drupal's Responsive Image module, where we'll be able to see it listed in the configuration form for creating a new responsive image style.
Customizing the available regions in your theme is one of the first things you'll do when creating your own themes. Doing so gives you complete control over where content is displayed on the page, and the markup involved. Adding regions to a theme is a two-step process that involves editing your theme's THEMENAME.info.yml file and updating your page.html.twig file.
In this tutorial we'll:
- Declare one or more new regions in our themes THEMENAME.info.yml file.
- Output the content of those regions in our theme via the page.html.twig file.
By the end of this tutorial you should be able to add or edit the regions a theme provides. Also, you'll ensure that blocks placed into regions are displayed by outputting the regions in the page template.
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.
Info files, aka THEMENAME.info.yml files, provide Drupal with metadata about your theme, the features it supports, and the regions that it defines. All themes are required to have a THEMENAME.info.yml file, and creating one is generally the first step you'll take when creating a new theme.
In this tutorial we'll:
- Create a new .info.yml file and define a new theme
- Review the required key/value pairs of an .info.yml file
- Enable our new theme in the Drupal UI
By the end of this tutorial you'll be able start a new theme by creating the required *.info.yml file and better understand its contents.
Themes and modules can alter the list of theme hook suggestions in order to add new ones, remove existing ones, or reorder the list. This powerful feature allows for the definition of custom logic in your application that can tell Drupal to use different templates based on your own unique needs. You might for example; use a different page template for authenticated users, or a custom block template for someone's birthday.
In this tutorial we'll cover:
- Adding new theme hook suggestions from a theme using
hook_theme_suggestions_HOOK_alter() - Altering the list of theme hook suggestions
- Removing theme hook suggestions
- Reordering the list of theme hook suggestions
Theme developers often need to add or remove classes and other attributes from an HTML tag. Template files handle this with a special Attributes object that contains the attributes and their values, as well as a handful of powerful methods to help manage these attributes.
In this tutorial we’ll cover:
- Adding/removing classes from elements in a Twig template
- The attributes object
- Examples of common tasks using various helper methods on the attributes object
One important aspect of theme administration is the configuration of global and theme-specific settings. In this tutorial, you will learn where theme settings are configured in Drupal's administrative interface, the difference between global and theme-specific settings, and what each global setting refers to on a base installation of Drupal with a custom theme installed.
One of the primary ways that modules extend Drupal is by adding dynamic pages with content generated by application-specific logic. This tutorial looks at Drupal's process of handling a user's request and transforming it into a complete web page. We'll answer questions like:
- How does Drupal use Symfony's HttpKernel to process requests?
- How do user-configured blocks and the theme layer contribute to the page's content and appearance?
- What is the role of routes, controllers, and responses in this process?
In this tutorial, we'll:
- Follow the journey of a user request from URL to an HTML response in Drupal.
- Define the role of routes, controllers, and responses in Drupal's request handling.
- See how blocks and the theme layer contribute to the final output of a Drupal page.
By the end of this tutorial, you should be able to describe Drupal's request flow, understand the interaction of its key components in building a page, and appreciate the modular architecture that drives Drupal's flexibility.
Custom themes in Drupal must be configured to inherit settings, templates, and other assets from a parent theme. Which base theme you use is configurable. This allows theme developers to use a different set of markup as the starting point for their theme, organize various theme assets into a more maintainable structure, and more. All of this is made possible because of how Drupal's theme layer uses a chain of inheritance when assembling all the parts of a theme.
Base themes are also a powerful way to encapsulate standards and best practices into a reusable code base. You'll find dozens of contributed base themes on Drupal.org that can serve as a great starting point, especially if you're planning to work with an existing design framework like Bootstrap or Susy Grids. Or if you want to leverage modern JavaScript bundling without setting up Webpack on your own.
In this tutorial we'll:
- Learn what base themes and subthemes are
- Look at a few examples of template inheritance and how that works
- Discuss some use cases for theme inheritance
By the end of this tutorial you'll know how to declare the base theme that your theme builds upon.
Making Drupal fast by default implies having caching layers and CSS and JavaScript aggregation utilities enabled out-of-the-box. As a theme developer this can be annoying, because you must clear these various caches in order to preview any changes. In addition, inspecting variables with debugging tools often produces PHP errors. We'll make some recommendations for PHP settings on your local environment that can prevent these errors from happening so often.
By the end of this tutorial, you should be able to:
- Set up your local Drupal site for theme development
- Prepare your local development environment for working on and debugging themes
Planning for a migration is essential. In our collective experience we've never once seen someone sit down and execute a migration flawlessly on their first attempt. Migrations involve preparing and analyzing your source data, building a new website that data can be migrated into, and lots of testing, rolling back, and testing again, in order to get everything right. By the end of this tutorial you should be ready to start planning for your own Drupal migration project, and have a better understanding of the challenges of migrating from one system to another.
In Twig, you can modify variables using functions or filters. Twig has a bunch of built-in functions and filters. Drupal extends Twig to provide a few handy Drupal-specific functions and filters.
In this tutorial, we'll look at:
- What are functions and filters?
- How to use functions and filters in Twig
- Detailed information about the Drupal-specific functions and filters, and their use case
Template files are used by modules when they need to add custom HTML to the content they output. The most common example is wrapping your output in one or more <div> tags to give it additional structure and context. Using custom template files in a Drupal module requires defining a new theme hook, creating the template file, an associating the appropriate data with the template file via a render array.
In this tutorial, we'll:
- Learn how to add a custom Twig template file to a module.
- Update the
WeatherPagecontroller to use the new template file.
By the end of this tutorial you should be able to create and use custom template files in a module.