mirror of
https://github.com/twbs/bootstrap.git
synced 2024-12-03 15:24:19 +01:00
125 lines
5.2 KiB
Markdown
125 lines
5.2 KiB
Markdown
---
|
|
layout: docs
|
|
title: Background
|
|
description: Convey meaning through `background-color` and add decoration with gradients.
|
|
group: utilities
|
|
toc: true
|
|
---
|
|
|
|
## 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" >}}).
|
|
|
|
{{< example >}}
|
|
{{< colors.inline >}}
|
|
{{- range (index $.Site.Data "theme-colors") }}
|
|
<div class="p-3 mb-2 bg-{{ .name }}{{ if .contrast_color }} text-{{ .contrast_color }}{{ else }} text-white{{ end }}">.bg-{{ .name }}</div>
|
|
{{- end -}}
|
|
{{< /colors.inline >}}
|
|
<div class="p-3 mb-2 bg-body text-dark">.bg-body</div>
|
|
<div class="p-3 mb-2 bg-white text-dark">.bg-white</div>
|
|
<div class="p-3 mb-2 bg-transparent text-dark">.bg-transparent</div>
|
|
{{< /example >}}
|
|
|
|
## 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") }}
|
|
<div class="p-3 mb-2 bg-{{ .name }} bg-gradient{{ with .contrast_color }} text-{{ . }}{{ else }} text-white{{ end }}">.bg-{{ .name }}.bg-gradient</div>
|
|
{{- end -}}
|
|
{{< /colors.inline >}}
|
|
{{< /markdown >}}
|
|
|
|
## Opacity
|
|
|
|
<small class="d-inline-flex px-2 py-1 font-monospace text-muted border rounded-3">Added in v5.1.0</small>
|
|
|
|
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.
|
|
|
|
```css
|
|
.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 >}}
|
|
<div class="bg-success p-2 text-white">This is default success background</div>
|
|
<div class="bg-success p-2" style="--bs-bg-opacity: .5;">This is 50% opacity success background</div>
|
|
{{< /example >}}
|
|
|
|
Or, choose from any of the `.bg-opacity` utilities:
|
|
|
|
{{< example >}}
|
|
<div class="bg-success p-2 text-white">This is default success background</div>
|
|
<div class="bg-success p-2 text-white bg-opacity-75">This is 75% opacity success background</div>
|
|
<div class="bg-success p-2 text-dark bg-opacity-50">This is 50% opacity success background</div>
|
|
<div class="bg-success p-2 text-dark bg-opacity-25">This is 25% opacity success background</div>
|
|
<div class="bg-success p-2 text-dark bg-opacity-10">This is 10% opacity success background</div>
|
|
{{< /example >}}
|
|
|
|
## Sass
|
|
|
|
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.
|
|
|
|
### 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" >}}
|
|
|
|
### Map
|
|
|
|
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/_variables.scss" >}}
|
|
|
|
And 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/_variables.scss" >}}
|
|
|
|
### 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" >}}
|