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06.

Assets: Custom CSS and JS

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The EasyAdmin interface looks pretty great out of the box. But what if we want to customize the way something looks? For example, if I want to change the background on the sidebar. How can we do that?

This type of stuff can be controlled via the configureAssets() method. As a reminder, this is one of those methods that exists inside both our dashboard controller and each individual CRUD controller. So we can control assets on a global level or for just one section.

Let's make our change globally so that we can change the color of the sidebar on every page.

Hello configureAssets()

Anywhere inside of DashboardController, go back to the "Code"->"Generate..." menu, select "Override Methods" and override configureAssets():

70 lines | src/Controller/Admin/DashboardController.php
// ... lines 1 - 10
use EasyCorp\Bundle\EasyAdminBundle\Config\Assets;
// ... lines 12 - 21
class DashboardController extends AbstractDashboardController
{
// ... lines 24 - 64
public function configureAssets(): Assets
{
return parent::configureAssets();
}
}

This has a lot of cool methods. There are some simple ones like ->addCssFile(). If you said ->addCssFile('foo.css'), that will include a link tag to /foo.css. As long as we have foo.css inside of our public/ directory, that would work.

The same thing goes for ->addJsFile(). And you can also ->addHtmlContentToBody() or ->addHtmlContentToHead(). There are tons of interesting methods!

Creating a Custom Admin Encore Entry

Our application uses Webpack Encore. Go check out the webpack.config.js file: it's pretty standard. We have just one entry called app:

76 lines | webpack.config.js
// ... lines 1 - 8
Encore
// ... lines 10 - 16
/*
* ENTRY CONFIG
*
* Each entry will result in one JavaScript file (e.g. app.js)
* and one CSS file (e.g. app.css) if your JavaScript imports CSS.
*/
.addEntry('app', './assets/app.js')
// ... lines 24 - 72
;
// ... lines 74 - 76

It's responsible for loading all of the JavaScript and CSS:

16 lines | assets/app.js
/*
* Welcome to your app's main JavaScript file!
*
* We recommend including the built version of this JavaScript file
* (and its CSS file) in your base layout (base.html.twig).
*/
// any CSS you import will output into a single css file (app.css in this case)
import './styles/app.css';
// start the Stimulus application
import './bootstrap';
// activates collapse functionality
import { Collapse } from 'bootstrap';

and we include this entry on our frontend to get everything looking and working well.

You probably noticed that, in configureAssets(), there's an addWebpackEncoreEntry() method. If we said app here, that would pull in the CSS and JavaScript from our app entry. But.... that makes things look a little crazy... because we do not want all of our frontend styles and JavaScript to show up in the admin section. Nope, we just want to be able to add a little bit of new stuff.

So here's what we'll do instead. Inside the assets/styles/ directory, create an entirely new file called admin.css. This will be our CSS solely for styling the admin section. And just to see if things are working, I'll add a very lovely body background of "lightcyan":

4 lines | assets/styles/admin.css
body {
background: lightcyan;
}

Fancy!

Over in webpack.config.js, add a second entry for just the admin. But, right now, since we only have a CSS file (we don't need JavaScript), I'll say .addStyleEntry()... and point it to ./assets/styles/admin.css. I should also change app to admin... but I'll catch that in a minute:

77 lines | webpack.config.js
// ... lines 1 - 8
Encore
// ... lines 10 - 23
.addStyleEntry('admin', './assets/styles/admin.css')
// ... lines 25 - 73
;
// ... lines 75 - 77

Because we just modified our webpack file, we need to go over to our terminal, find where we're running encore, hit Ctrl+C, and then rerun it:

yarn watch

And... it exploded! That's from my mistake! I need to give my entry a unique name. Change app to admin:

77 lines | webpack.config.js
// ... lines 1 - 8
Encore
// ... lines 10 - 23
.addStyleEntry('admin', './assets/styles/admin.css')
// ... lines 25 - 73
;
// ... lines 75 - 77

Run it again, and... beautiful!

In addition to the original stuff, you can see that it also dumped an admin.css file. Thanks to this, over in our DashboardController, say ->addWebpackEncoreEntry('admin'):

71 lines | src/Controller/Admin/DashboardController.php
// ... lines 1 - 21
class DashboardController extends AbstractDashboardController
{
// ... lines 24 - 64
public function configureAssets(): Assets
{
return parent::configureAssets()
->addWebpackEncoreEntry('admin');
}
}

Refresh and... it works! That's a... well... interesting-looking page.

If you View the page source, you can see how this works. There's really nothing special. The app.css file gives us all of the EasyAdmin styling that we've been enjoying... and then here is our new admin.css file.

CSS Properties

At this point, we're dangerous! We can add whatever CSS we want to the new admin.css file and it will override any of the EasyAdmin styles. Cool! But EasyAdmin makes it even easier than that!

Inspect the element on the sidebar. The goal is to change the sidebar background. Find the actual element with the sidebar class. If you look over at the styles on the right... I'll make this a little bit bigger... you can see that the .sidebar class has a background style. But instead of it being set to a color, it's set to this var(--sidebar-bg) thing. If you hover over it, apparently, this is equal to #f8fafc.

If you haven't seen this before, this is a CSS property. It has nothing to do with EasyAdmin or Symfony. In CSS, you can create variables (called "CSS properties") and reference them somewhere else. EasyAdmin, apparently, created a --sidebar-bg variable and is referencing it here. So, instead of trying to override the background of .sidebar - which we could do - we can override this CSS property and it will have the same effect.

How? Let's cheat a little bit by digging deep into EasyAdmin itself.

Open vendor/easycorp/easyadmin-bundle/assets/css/easyadmin-theme/. Inside, there's a file called variables-theme.scss. This is where all of these CSS properties are defined. And there's tons of stuff here, for font sizes, different widths, and... --sidebar-bg! This --sidebar-bg variable, or property, is apparently set to another variable via the var syntax. You'll find that variable in another file called ./color-palette.scss... which is right here. These are SCSS files, but this CSS property system has nothing to do with Sass. This is a pure CSS feature.

There's a lot here, but if you follow the logic, --sidebar-bg is set to --gray-50... then all the way at the bottom, --gray-50 is set to --blue-gray-50... then that... if we keep looking... yes! It's set to the color we expected!

This is a great way to learn what these values are, how they relate to one another and how to override them. Copy the --sidebar-bg syntax.

The way you define CSS variables is typically under this :root pseudo-selector. We're going to do the same thing.

In our CSS file, remove the body, add :root and then paste. And while it's totally legal to reference CSS properties from here, let's replace that with a normal hex color:

2 lines | assets/styles/admin.css
:root { --sidebar-bg: #deebff; }

Let's try it! Watch the sidebar closely... the change is subtle. Refresh and... it changed! To prove it, if you find the --sidebar-bg on the styles and hover... that property is now set to #deebff. It's subtle, but it is loading the correct color!

So we just customized the assets globally for our entire admin section. But we could override configureAssets() in a specific CRUD controller to make changes that only apply to that section.

Next, let's start digging into what is quite possibly the most important part of configuring EasyAdmin: Fields. These control which fields show up on the index page, as well as the form pages.