* Tweak callout for icon link - no need to talk about `alt` for `<img>` since these don't use `<img>` - make start of sentence more readable * Tweak language of dropdown warning callout * Tweak popover warning callout * Tweak rtl warning callouts * Tweak color warning callout * Add/move accessibility callout for color to relevant pages * Update site/content/docs/5.3/helpers/icon-link.md * Update site/layouts/partials/callouts/warning-color-assistive-technologies.md Co-authored-by: Mark Otto <markd.otto@gmail.com>
6.3 KiB
layout | title | description | group | toc |
---|---|---|---|---|
docs | Background | Convey meaning through `background-color` and add decoration with gradients. | utilities | true |
{{< callout info >}} {{< partial "callouts/warning-color-assistive-technologies.md" >}} {{< /callout >}}
Background color
Similar to the contextual text color classes, set the background of an element to any contextual class. Background utilities do not set color
, so in some cases you'll want to use .text-*
[color utilities]({{< docsref "/utilities/colors" >}}).
{{< callout info >}}
Background utilities like .bg-*
that generated from our original $theme-colors
Sass map don't yet respond to color modes, however, any .bg-*-subtle
utility will. This will be resolved in v6.
{{< /callout >}}
{{< example >}} {{< colors.inline >}} {{- range (index $.Site.Data "theme-colors") }}
.bg-body-secondary
.bg-body-tertiary
Background gradient
By adding a .bg-gradient
class, a linear gradient is added as background image to the backgrounds. This gradient starts with a semi-transparent white which fades out to the bottom.
Do you need a gradient in your custom CSS? Just add background-image: var(--bs-gradient);
.
{{< markdown >}} {{< colors.inline >}} {{- range (index $.Site.Data "theme-colors") }}
Opacity
{{< added-in "5.1.0" >}}
As of v5.1.0, background-color
utilities are generated with Sass using CSS variables. This allows for real-time color changes without compilation and dynamic alpha transparency changes.
How it works
Consider our default .bg-success
utility.
.bg-success {
--bs-bg-opacity: 1;
background-color: rgba(var(--bs-success-rgb), var(--bs-bg-opacity)) !important;
}
We use an RGB version of our --bs-success
(with the value of 25, 135, 84
) CSS variable and attached a second CSS variable, --bs-bg-opacity
, for the alpha transparency (with a default value 1
thanks to a local CSS variable). That means anytime you use .bg-success
now, your computed color
value is rgba(25, 135, 84, 1)
. The local CSS variable inside each .bg-*
class avoids inheritance issues so nested instances of the utilities don't automatically have a modified alpha transparency.
Example
To change that opacity, override --bs-bg-opacity
via custom styles or inline styles.
{{< example >}}
Or, choose from any of the .bg-opacity
utilities:
{{< example >}}
CSS
In addition to the following Sass functionality, consider reading about our included [CSS custom properties]({{< docsref "/customize/css-variables" >}}) (aka CSS variables) for colors and more.
Sass variables
Most background-color
utilities are generated by our theme colors, reassigned from our generic color palette variables.
{{< scss-docs name="color-variables" file="scss/_variables.scss" >}}
{{< scss-docs name="theme-color-variables" file="scss/_variables.scss" >}}
{{< scss-docs name="variable-gradient" file="scss/_variables.scss" >}}
Grayscale colors are also available, but only a subset are used to generate any utilities.
{{< scss-docs name="gray-color-variables" file="scss/_variables.scss" >}}
Variables for setting background-color
in .bg-*-subtle
utilities in light and dark mode:
{{< scss-docs name="theme-bg-subtle-variables" file="scss/_variables.scss" >}}
{{< scss-docs name="theme-bg-subtle-dark-variables" file="scss/_variables-dark.scss" >}}
Sass maps
Theme colors are then put into a Sass map so we can loop over them to generate our utilities, component modifiers, and more.
{{< scss-docs name="theme-colors-map" file="scss/_variables.scss" >}}
Grayscale colors are also available as a Sass map. This map is not used to generate any utilities.
{{< scss-docs name="gray-colors-map" file="scss/_variables.scss" >}}
RGB colors are generated from a separate Sass map:
{{< scss-docs name="theme-colors-rgb" file="scss/_maps.scss" >}}
Background color opacities build on that with their own map that's consumed by the utilities API:
{{< scss-docs name="utilities-bg-colors" file="scss/_maps.scss" >}}
Color mode background colors are also available as a Sass map:
{{< scss-docs name="theme-bg-subtle-map" file="scss/_maps.scss" >}}
{{< scss-docs name="theme-bg-subtle-dark-map" file="scss/_maps.scss" >}}
Sass mixins
No mixins are used to generate our background utilities, but we do have some additional mixins for other situations where you'd like to create your own gradients.
{{< scss-docs name="gradient-bg-mixin" file="scss/mixins/_gradients.scss" >}}
{{< scss-docs name="gradient-mixins" file="scss/mixins/_gradients.scss" >}}
Utilities API
Background utilities are declared in our utilities API in scss/_utilities.scss
. [Learn how to use the utilities API.]({{< docsref "/utilities/api#using-the-api" >}})
{{< scss-docs name="utils-bg-color" file="scss/_utilities.scss" >}}