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3rd Party CSS


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We talked about adding CSS to our site, but what about third-party CSS like Bootstrap? With a build system such as Encore, we have a package.json file, and we can run:

npm install bootstrap

In AssetMapper, because there's no Node, we don't have a such an easy system for grabbing CSS packages. But we can still get them.

Finding Packages on jsDelivr

I like to use jsDelivr for this: a CDN for all NPM packages. Even if you don't ultimately use it as a CDN, it's a nice way to find and download what you need.

Search for "Bootstrap" and... there it is. A lot of times, you'll find the CSS file you need right up here, like this. I'll hit "Copy HTML + SRI". If you don't see the CSS file here... or you need a different one, you can click the "Files" tab to browse the entire package. For example - dist/css/ and then whatever you need.

Okay, we know that CSS with AssetMapper is delightfully boring... so go back over to the stylesheets block and, above styles/app.css, paste the new link tag.

74 lines | templates/base.html.twig
// ... lines 1 - 2
// ... lines 4 - 11
{% block stylesheets %}
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css" integrity="sha256-fx038NkLY4U1TCrBDiu5FWPEa9eiZu01EiLryshJbCo=" crossorigin="anonymous">
// ... line 14
{% endblock %}
// ... lines 16 - 20
// ... lines 22 - 74

If you want to avoid using the CDN, you could download this file directly into your project. Because there's no package system like NPM, I would probably create an assets/vendor/ directory and put the file inside of that. Then I would commit that assets/vendor/ directory to Git to keep it in your project and versioned. Committing vendor files into your project isn't amazing, but it's not a huge deal and is your best option right now if you want to avoid a CDN. You'll see me do this later for a JavaScript. file.

Ok, let's see if this is working! Scroll down to the middle of the page and add a button with btn btn-primary to use a few common Bootstrap styles.

74 lines | templates/base.html.twig
// ... lines 1 - 21
<body class="bg-gray-800 text-white">
// ... lines 23 - 50
<button class="btn btn-primary">Primary Button</button>
// ... lines 52 - 71
// ... lines 73 - 74

When we head over to the site and refresh... it works! Lovely!

Bootstrap Sass?

Ok, but what if I want to modify Bootstrap? Bootstrap itself is built with Sass. So, if you want, you can build Sass files that override Bootstrap variables - for example to change default colors.

There are two important things about this. First, you absolutely can use Sass with AssetMapper. There are details in the documentation about how to do that... and hopefully we'll add a bundle soon to make it even easier.

Go Deeper!

Also, in a moment, we're going to add Tailwind CSS to our site, which doesn't require Sass, but has a very similar workflow because Tailwind needs to be "built".

And, if you do want to use Sass with Bootstrap, one simple way get the Bootstrap source code is via the official Composer package for Bootstrap - so:

composer require twbs/bootstrap

If this is something you want, check out the AssetMapper docs.

Bootstrap CSS Variables

The second important thing is that, depending on what you want to do, you may not need to use Sass to customize Bootstrap. That's because Bootstrap also exposes CSS variables, though they're not as powerful.

We can see this down in the "Customize" "CSS Variables" section. CSS variables are a browser feature that allow you to set variables inside of CSS then reference them. No fancy-pants Sass needed.

For example, over in app.css... on top... add a :root pseudo selector, which is a common place to initialize variables that will be used later. Here, override a CSS variable that Bootstrap provides and uses: --bs-border-radius. Set it to 1rem.

15 lines | assets/styles/app.css
:root {
--bs-border-radius: 1rem;
// ... lines 4 - 15

That should make the borders noticeably larger. Back at the browser... it works! The border radius is now larger across the site. That's one of the variables you would find in the Bootstrap documentation.

However, it's not always this simple. Let's say we want to override this primary color. You might think you could do that by searching for "primary"... up here... and overriding something like --bs-primary. That's sort of correct.

If you inspect our button, this color is the actual background color. But watch. Try to override that by changing it to a slightly lighter color. Then head back and try it. It doesn't do anything.

16 lines | assets/styles/app.css
:root {
--bs-primary: #0de1fd;
// ... line 3
// ... lines 5 - 16

Copy the CDN URL, pop that into your browser, and take off the .min so we can see what's going on. On top, it's setting all of those nice CSS variables. Look for btn-primary. I won't get too deep here, but inside of .btn-primary, it's setting these CSS variables to these hard-coded colors, instead of using other CSS variables that we can control.

So what do we do? In this case, we're kind of back to the basic strategy of overriding CSS... though we can at least use CSS variables when we do this.

Spin back over to app.css and I'll paste in some styling for .btn-primary. This overrides the variables that are set by Bootstrap to a different color. We are, at least, using the bs-primary variable: we set it up here, and can reference it in as many spots as we want. So, pretty basic CSS overriding, but with less repetition.

24 lines | assets/styles/app.css
// ... lines 1 - 4
.btn-primary {
--bs-btn-bg: var(--bs-primary);
--bs-btn-border-color: var(--bs-primary);
--bs-btn-disabled-bg: var(--bs-primary);
--bs-btn-disabled-border-color: var(--bs-primary);
--bs-btn-hover-bg: #0bbfd7;
--bs-btn-hover-border-color: #0ba7d7;
// ... lines 13 - 24

And when we try it... it does change the color. Sweet! So CSS variables are one way to customize Bootstrap, but Sass is still an even more powerful option.

Next: let's grab one more external styling thing: an open source font!