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Utilize our source Sass files to take advantage of variables, maps, mixins, and functions to help you build faster and customize your project.

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Utilize our source Sass files to take advantage of variables, maps, mixins, and more.

File structure#

Whenever possible, avoid modifying CoreUI's core files. For Sass, that means creating your own stylesheet that imports CoreUI for Bootstrap so you can modify and extend it. Assuming you're using a package manager like npm, you'll have a file structure that looks like this:

your-project/
├── scss
│   └── custom.scss
└── node_modules/
    └── @coreui/coreui
        ├── js
        └── scss

If you've downloaded our source files and aren't using a package manager, you'll want to manually create something similar to that structure, keeping CoreUI's source files separate from your own.

your-project/
├── scss
│   └── custom.scss
└── @coreui/coreui/
    ├── js
    └── scss

Importing#

In your custom.scss, you'll import CoreUI's source Sass files. You have two options: include all of CoreUI, or pick the parts you need. We encourage the latter, though be aware there are some requirements and dependencies across our components. You also will need to include some JavaScript for our plugins.

// Custom.scss
// Option A: Include all of CoreUI

@import "../node_modules/@coreui/coreui/scss/coreui";

// Then add additional custom code here

// Custom.scss
// Option B: Include parts of CoreUI

// 1. Include functions first (so you can manipulate colors, SVGs, calc, etc)
@import "../node_modules/@coreui/coreui/scss/functions";

// 2. Include any default variable overrides here

// 3. Include remainder of required CoreUI stylesheets
@import "../node_modules/@coreui/coreui/scss/variables";

// 4. Include any default map overrides here

// 5. Include remainder of required parts
@import "../node_modules/@coreui/coreui/scss/maps";
@import "../node_modules/@coreui/coreui/scss/mixins";
@import "../node_modules/@coreui/coreui/scss/root";

// 6. Optionally include any other parts as needed
@import "../node_modules/@coreui/coreui/scss/utilities";
@import "../node_modules/@coreui/coreui/scss/reboot";
@import "../node_modules/@coreui/coreui/scss/type";
@import "../node_modules/@coreui/coreui/scss/images";
@import "../node_modules/@coreui/coreui/scss/containers";
@import "../node_modules/@coreui/coreui/scss/grid";
@import "../node_modules/@coreui/coreui/scss/helpers";

// 7. Optionally include utilities API last to generate classes based on the Sass map in `_utilities.scss`
@import "../node_modules/@coreui/coreui/scss/utilities/api";

// 8. Add additional custom code here

With that setup in place, you can begin to modify any of the Sass variables and maps in your custom.scss. You can also start to add parts of CoreUI for Bootstrap under the // Optional section as needed. We suggest using the full import stack from our coreui.scss file as your starting point.

Variable defaults#

Every Sass variable in CoreUI for Bootstrap includes the !default flag allowing you to override the variable's default value in your own Sass without modifying CoreUI's source code. Copy and paste variables as needed, modify their values, and remove the !default flag. If a variable has already been assigned, then it won't be re-assigned by the default values in Bootstrap.

You will find the complete list of CoreUI's variables in @coreui/coreui/scss/_variables.scss. Some variables are set to null, these variables don't output the property unless they are overridden in your configuration.

Variable overrides must come after our functions are imported, but before the rest of the imports.

Here's an example that changes the background-color and color for the <body> when importing and compiling CoreUI for Bootstrap via npm:

// Required
@import "../node_modules/@coreui/coreui/scss/functions";

// Default variable overrides
$body-bg: #000;
$body-color: #111;

// Required
@import "../node_modules/@coreui/coreui/scss/variables";
@import "../node_modules/@coreui/coreui/scss/maps";
@import "../node_modules/@coreui/coreui/scss/mixins";
@import "../node_modules/@coreui/coreui/scss/root";

// Optional CoreUI components here
@import "../node_modules/@coreui/coreui/scss/reboot";
@import "../node_modules/@coreui/coreui/scss/type";
// etc

Repeat as necessary for any variable in CoreUI, including the global options below.

Maps and loops#

CoreUI for Bootstrap includes a handful of Sass maps, key value pairs that make it easier to generate families of related CSS. We use Sass maps for our colors, grid breakpoints, and more. Just like Sass variables, all Sass maps include the !default flag and can be overridden and extended.

Some of our Sass maps are merged into empty ones by default. This is done to allow easy expansion of a given Sass map, but comes at the cost of making removing items from a map slightly more difficult.

Modify map#

All variables in the $theme-colors map are defined as standalone variables. To modify an existing color in our $theme-colors map, add the following to your custom Sass file:

$primary: #0074d9;
$danger: #ff4136;

Later on, these variables are set in CoreUI's $theme-colors map:

$theme-colors: (
  "primary": $primary,
  "danger": $danger
);

Add to map#

Add new colors to $theme-colors, or any other map, by creating a new Sass map with your custom values and merging it with the original map. In this case, we'll create a new $custom-colors map and merge it with $theme-colors.

// Create your own map
$custom-colors: (
  "custom-color": #900
);

// Merge the maps
$theme-colors: map-merge($theme-colors, $custom-colors);

Remove from map#

To remove colors from $theme-colors, or any other map, use map-remove. Be aware you must insert it between our requirements and options:

// Required
@import "../node_modules/@coreui/coreui/scss/functions";
@import "../node_modules/@coreui/coreui/scss/variables";
@import "../node_modules/@coreui/coreui/scss/maps";
@import "../node_modules/@coreui/coreui/scss/mixins";
@import "../node_modules/@coreui/coreui/scss/root";

$theme-colors: map-remove($theme-colors, "info", "light", "dark");

// Optional
@import "../node_modules/@coreui/coreui/scss/reboot";
@import "../node_modules/@coreui/coreui/scss/type";
// etc

Required keys#

CoreUI for Bootstrap assumes the presence of some specific keys within Sass maps as we used and extend these ourselves. As you customize the included maps, you may encounter errors where a specific Sass map's key is being used.

For example, we use the primary, success, and danger keys from $theme-colors for links, buttons, and form states. Replacing the values of these keys should present no issues, but removing them may cause Sass compilation issues. In these instances, you'll need to modify the Sass code that makes use of those values.

Functions#

Colors#

Next to the Sass maps we have, theme colors can also be used as standalone variables, like $primary.

.custom-element {
  color: $gray-100;
  background-color: $dark;
}

You can lighten or darken colors with CoreUI's tint-color() and shade-color() functions. These functions will mix colors with black or white, unlike Sass' native lighten() and darken() functions which will change the lightness by a fixed amount, which often doesn't lead to the desired effect.

// Tint a color: mix a color with white
@function tint-color($color, $weight) {
  @return mix(white, $color, $weight);
}

// Shade a color: mix a color with black
@function shade-color($color, $weight) {
  @return mix(black, $color, $weight);
}

// Shade the color if the weight is positive, else tint it
@function shift-color($color, $weight) {
  @return if($weight > 0, shade-color($color, $weight), tint-color($color, -$weight));
}

In practice, you'd call the function and pass in the color and weight parameters.

.custom-element {
  color: tint-color($primary, 10%);
}

.custom-element-2 {
  color: shade-color($danger, 30%);
}

Color contrast#

In order to meet the Web Content Accessibility Guidelines (WCAG) contrast requirements, authors must provide a minimum text color contrast of 4.5:1 and a minimum non-text color contrast of 3:1, with very few exceptions.

An additional function we include in CoreUI for Bootstrap is the color contrast function, color-contrast. It utilizes the WCAG 2.0 algorithm for calculating contrast thresholds based on relative luminance in a sRGB colorspace to automatically return a light (#fff), dark (#212529) or black (#000) contrast color based on the specified base color. This function is especially useful for mixins or loops where you're generating multiple classes.

For example, to generate color swatches from our $theme-colors map:

@each $color, $value in $theme-colors {
  .swatch-#{$color} {
    color: color-contrast($value);
  }
}

It can also be used for one-off contrast needs:

.custom-element {
  color: color-contrast(#000); // returns `color: #fff`
}

You can also specify a base color with our color map functions:

.custom-element {
  color: color-contrast($dark); // returns `color: #fff`
}

Escape SVG#

We use the escape-svg function to escape the <, > and # characters for SVG background images. When using the escape-svg function, data URIs must be quoted.

Add and Subtract functions#

We use the add and subtract functions to wrap the CSS calc function. The primary purpose of these functions is to avoid errors when a "unitless" 0 value is passed into a calc expression. Expressions like calc(10px - 0) will return an error in all browsers, despite being mathematically correct.

Example where the calc is valid:

$border-radius: .25rem;
$border-width: 1px;

.element {
  // Output calc(.25rem - 1px) is valid
  border-radius: calc($border-radius - $border-width);
}

.element {
  // Output the same calc(.25rem - 1px) as above
  border-radius: subtract($border-radius, $border-width);
}

Example where the calc is invalid:

$border-radius: .25rem;
$border-width: 0;

.element {
  // Output calc(.25rem - 0) is invalid
  border-radius: calc($border-radius - $border-width);
}

.element {
  // Output .25rem
  border-radius: subtract($border-radius, $border-width);
}

Mixins#

Our @coreui/coreui/scss/mixins/ directory has a ton of mixins that power parts of CoreUI and can also be used across your own project.

Color schemes#

A shorthand mixin for the prefers-color-scheme media query is available with support for light, dark, and custom color schemes.

@mixin color-scheme($name) {
  @media (prefers-color-scheme: #{$name}) {
    @content;
  }
}

.custom-element {
  @include color-scheme(dark) {
    // Insert dark mode styles here
  }

  @include color-scheme(custom-named-scheme) {
    // Insert custom color scheme styles here
  }
}