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Tweaking Bootstrap's Sass

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Now that we finally have Bootstrap's Sass working, we can celebrate! Inside _bootstrap.scss, the first thing it imports is an _variables.scss file. I'll hold Command and click to open that.

Awesome! This holds a bunch of variables that are used throughout the rest of the Sass files. Yep, this means we can override these to control colors and many other things.

Copy the $brand-primary variable line. Then, at the top of our main.scss file, before we import Bootstrap, override that variable. Make sure to remove the default.

This variable is used to color some buttons and a lot of other things. Let's make it a little lighter: change the 6.5 to 2.5. It's not important, but the new color should be #3885C7:

82 lines | assets/css/main.scss
$brand-primary: darken(#428bca, 2.5%); // #3885c7
// ... lines 2 - 82

Back in the browser, inspect the "I Lifted It!" button. Yep! The current color is #337AB7. Now, refresh! Check it out. Yes! It's the slightly lighter #3885C7.

So this is really the reason why you might want to import Bootstrap as Sass, instead of CSS.

Importing Only Parts of Bootstrap

Let's do one more thing! The _bootstrap.scss file imports every part of Bootstrap. But what if you don't need every part of Bootstrap? For example, we are not using the glyphicons. Importing that CSS is wasteful!

Let's fix this! Copy the entire contents of _bootstrap.scss. Then, in our css/ directory, create a new _bootstrap.scss file and paste that here.

As soon as we do that... all the paths are broken! Yea, that makes sense: we're in a different directory. No problem, I'll copy "bootstrap and do a "Find and Replace" to replace this with "~bootstrap-sass/assets/stylesheets/bootstrap. Replace everything!

// Core variables and mixins
@import "~bootstrap-sass/assets/stylesheets/bootstrap/variables";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/mixins";
// Reset and dependencies
@import "~bootstrap-sass/assets/stylesheets/bootstrap/normalize";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/print";
//@import "~bootstrap-sass/assets/stylesheets/bootstrap/glyphicons";
// Core CSS
@import "~bootstrap-sass/assets/stylesheets/bootstrap/scaffolding";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/type";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/code";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/grid";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/tables";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/forms";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/buttons";
// Components
@import "~bootstrap-sass/assets/stylesheets/bootstrap/component-animations";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/dropdowns";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/button-groups";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/input-groups";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/navs";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/navbar";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/breadcrumbs";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/pagination";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/pager";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/labels";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/badges";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/jumbotron";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/thumbnails";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/alerts";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/progress-bars";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/media";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/list-group";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/panels";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/responsive-embed";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/wells";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/close";
// Components w/ JavaScript
@import "~bootstrap-sass/assets/stylesheets/bootstrap/modals";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/tooltip";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/popovers";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/carousel";
// Utility classes
@import "~bootstrap-sass/assets/stylesheets/bootstrap/utilities";
@import "~bootstrap-sass/assets/stylesheets/bootstrap/responsive-utilities";

Yay! Happy paths!

Next, in main.scss, import this file instead of the core one. Just, ./_bootstrap.scss.:

82 lines | assets/css/main.scss
// ... lines 1 - 2
@import './_bootstrap.scss';
// ... lines 4 - 82

If this is all we did, nothing would change: we're still importing everything. But now... we have power! In _bootstrap.scss, comment out the glyphicons line:

51 lines | assets/css/_bootstrap.scss
// ... lines 1 - 7
//@import "~bootstrap-sass/assets/stylesheets/bootstrap/glyphicons";
// ... lines 9 - 51

Cool! We don't need to restart Webpack after this change, but, stop it temporarily so that we can clean out the build/ directory:

rm -rf web/build/*

Now, re-run webpack:

./node_modules/.bin/webpack --watch

Check it out! In web/build, we still have the Font Awesome fonts... but we do not have the glyphicon fonts anymore. That's awesome! We're not parsing the _glyphicons.scss file anymore, so Webpack never sees those font files and so never moves them. This is proof that our CSS file is now just a little bit smaller.

Ok, let's add some sourcemaps to make debugging a lot nicer.