Overview
<b-overlay> can be used to obscure almost anything. Example use cases would be forms, tables, delete confirmation dialogs, or anywhere you need to signal that the application is busy performing a background task, to signal that a certain component is unavailable, or to provide additional context to the end user.
<b-overlay> can be used to overlay (wrap) an element or component (the default behaviour), or can be placed as a descendant of a position: relative element (non-wrapping mode).
The overlay visibility is controlled via the show prop. By default the overlay is not shown.
Note that this component only visually obscures its content (or the page). Refer to the Accessibility section below for additional accessibility details and concerns.
Default wrapping mode example:
<template>
<div>
<b-overlay :show="show" rounded="sm">
<b-card title="Card with overlay" :aria-hidden="show ? 'true' : null">
<b-card-text>Laborum consequat non elit enim exercitation cillum.</b-card-text>
<b-card-text>Click the button to toggle the overlay:</b-card-text>
<b-button :disabled="show" variant="primary" @click="show = true">
Show overlay
</b-button>
</b-card>
</b-overlay>
<b-button class="mt-3" @click="show = !show">Toggle overlay</b-button>
</div>
</template>
<script>
export default {
data() {
return {
show: false
}
}
}
</script>
Options
There are many options available for styling the overlay, and for providing custom content within the overlay.
Overlay backdrop color
You can control the backdrop background color via the variant prop. The variant is translated into one of Bootstrap's background variant utility classes. Control the opacity of the backdrop via the opacity prop (opacity values can range from 0 to 1). And background blurring can be controlled via the blur prop.
<template>
<div>
<b-row>
<b-col lg="6" aria-controls="overlay-background">
<b-form-group label="Variant" label-for="bg-variant" label-cols-sm="4" label-cols-lg="12">
<b-form-select id="bg-variant" v-model="variant" :options="variants"></b-form-select>
</b-form-group>
<b-form-group label="Opacity" label-for="bg-opacity" label-cols-sm="4" label-cols-lg="12">
<b-input-group>
<b-form-input
id="bg-opacity"
v-model="opacity"
type="range"
number
min="0"
max="1"
step="0.01"
></b-form-input>
<b-input-group-append is-text class="text-monospace">
{{ opacity.toFixed(2) }}
</b-input-group-append>
</b-input-group>
</b-form-group>
<b-form-group label="Blur" label-for="bg-blur" label-cols-sm="4" label-cols-lg="12">
<b-form-select id="bg-blur" v-model="blur" :options="blurs"></b-form-select>
</b-form-group>
</b-col>
<b-col lg="6">
<b-overlay
id="overlay-background"
show
:variant="variant"
:opacity="opacity"
:blur="blur"
rounded="sm"
>
<b-card title="Card with overlay" aria-hidden="true">
<b-card-text>
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud
exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</b-card-text>
<b-button disabled variant="primary">Button</b-button>
</b-card>
</b-overlay>
</b-col>
</b-row>
</div>
</template>
<script>
export default {
data() {
return {
variant: 'light',
opacity: 0.85,
blur: '2px',
variants: [
'transparent',
'white',
'light',
'dark',
'primary',
'secondary',
'success',
'danger',
'warning',
'info',
],
blurs: [
{ text: 'None', value: '' },
'1px',
'2px',
'5px',
'0.5em',
'1rem'
]
}
}
}
</script>
As an alternative to the variant prop, you can specify a CSS color string value via the bg-color prop. When a value is provided for bg-color, the variant prop value is ignored.
Notes:
- Background blurring is not available on some browsers (e.g. IE 11).
- Blurring requires that the opacity level be relatively high for the effect to be visible.
Fade transition
By default, the overlay uses Bootstrap's fade transition when showing or hiding. You can disable the fade transition via adding the no-fade prop to <b-overlay>.
Default spinner styling
The default overlay content is a <b-spinner> of type 'border'. You can control the appearance of the spinner via the following props:
spinner-type: Currently supported values are 'border' (the default) or 'grow'.spinner-variant: Variant theme color for the spinner. Default is null which inherits the current font color.spinner-small: Set to true to render a small size spinner.
<template>
<div>
<b-overlay
show
spinner-variant="primary"
spinner-type="grow"
spinner-small
rounded="sm"
style="max-width: 320px;"
>
<b-card title="Card with spinner style" aria-hidden="true">
<b-card-text>
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud
exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</b-card-text>
<b-button disabled variant="primary">Button</b-button>
</b-card>
</b-overlay>
</div>
</template>
Overlay corner rounding
By default, the overlay backdrop has square corners. If the content you are wrapping has rounded corners, you can use the rounded prop to apply rounding to the overlay's corners to match the obscured content's rounded corners.
Possible values are:
true (or the empty string '') to apply default (medium) roundingfalse (the default) applies no rounding to the backdrop overlay'sm' for small rounded corners'lg' for large rounded corners'pill' for pill style rounded corners'circle' for circular (or oval) rounding'top' for rounding only the top two corners'bottom' for rounding only the bottom two corners'left' for rounding only the two left corners'right' for rounding only the two right corners
<template>
<div>
<b-button @click="show = !show">Toggle overlay</b-button>
<b-row class="text-center mt-3">
<b-col md="6">
<p>With rounding</p>
<b-overlay :show="show" class="d-inline-block" rounded="circle">
<b-img thumbnail rounded="circle" fluid src="https://picsum.photos/200/200/?image=54" alt="Image 1"></b-img>
</b-overlay>
</b-col>
<b-col md="6">
<p>Without rounding</p>
<b-overlay :show="show" class="d-inline-block">
<b-img thumbnail rounded="circle" fluid src="https://picsum.photos/200/200/?image=54" alt="Image 1"></b-img>
</b-overlay>
</b-col>
</b-row>
</div>
</template>
<script>
export default {
data() {
return {
show: true
}
}
}
</script>
Custom overlay content
Place custom content in the overlay (replacing the default spinner) via the optionally scoped slot overlay.
<template>
<div>
<b-overlay :show="show" rounded="sm" @shown="onShown" @hidden="onHidden">
<b-card title="Card with custom overlay content" :aria-hidden="show ? 'true' : null">
<b-card-text>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</b-card-text>
<b-card-text>Click the button to toggle the overlay:</b-card-text>
<b-button ref="show" :disabled="show" variant="primary" @click="show = true">
Show overlay
</b-button>
</b-card>
<template #overlay>
<div class="text-center">
<b-icon icon="stopwatch" font-scale="3" animation="cylon"></b-icon>
<p id="cancel-label">Please wait...</p>
<b-button
ref="cancel"
variant="outline-danger"
size="sm"
aria-describedby="cancel-label"
@click="show = false"
>
Cancel
</b-button>
</div>
</template>
</b-overlay>
</div>
</template>
<script>
export default {
data() {
return {
show: false
}
},
methods: {
onShown() {
this.$refs.cancel.focus()
},
onHidden() {
this.$refs.show.focus()
}
}
}
</script>
The following scope properties are available to the overlay slot:
| Property | Description |
spinnerVariant | Value of the spinner-variant prop |
spinnerType | Value of the spinner-type prop |
spinnerSmall | Value of the spinner-small prop |
When placing interactive content in the overlay, you should focus the container of the custom content or one of the focusable controls in the overlay content for accessibility reasons. You can listen for the <b-overlay> 'shown' event to know when the overlay content is available in the document.
Overlay content centering
By default the overlay content will be horizontally and vertically centered within the overlay region. To disable centering, set the no-center prop to true.
In the following example, we have set the no-center prop, and absolutely positioned the custom overlay slot content at the top right.
<template>
<div>
<b-overlay no-center show rounded="sm">
<template #overlay>
<b-icon
icon="stopwatch"
variant="info"
scale="2"
shift-v="8"
shift-h="8"
class="position-absolute"
style="top: 0; right: 0"
></b-icon>
</template>
<b-card title="Card with no-center overlay" aria-hidden="true">
<b-card-text>
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
incididunt ut labore et dolore magna aliqua.
</b-card-text>
<b-button disabled variant="primary">Button</b-button>
</b-card>
</b-overlay>
</div>
</template>
Width
<b-overlay> defaults to a width of 100%. When wrapping an inline or inline-block element, you will need to add the class d-inline-block (e.g. <b-overlay class="d-inline-block">).
You can also use the width utility classes or CSS styles to control the width of the overlay's wrapping container element.
Non-wrapping mode
By default, <b-overlay> wraps the content of the default slot. In some cases you may want to obscure a parent container. Use the no-wrap prop to disable rendering of the wrapping (and ignore the default slot). Note that this requires that the ancestor element that is to be obscured to have relative positioning (either via the utility class 'position-relative', or CSS style 'position: relative;').
<template>
<div>
<div class="position-relative p-4 bg-info">
<p class="text-light font-weight-bold">
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
</p>
<b-card title="Card with parent overlay">
<b-card-text>Laborum consequat non elit enim exercitation cillum.</b-card-text>
<b-card-text>Click the button to toggle the overlay:</b-card-text>
<b-button :disabled="show" variant="primary" @click="show = true">
Show overlay
</b-button>
</b-card>
<p class="text-light font-weight-bold mb-0">
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
</p>
<b-overlay :show="show" no-wrap>
</b-overlay>
</div>
<b-button class="mt-3" @click="show = !show">Toggle overlay</b-button>
</div>
</template>
<script>
export default {
data() {
return {
show: false
}
}
}
</script>
Note that some of Bootstrap v4's component styles have relative positioning defined (e.g. cards, cols, etc.). You may need to adjust the placement of <b-overlay> in your markup.
For example, <b-card> has relative positioning, so you can place the <b-overlay no-wrap> as a descendant of <b-card>:
<template>
<div>
<b-card header="Card header" footer="Card footer">
<b-media>
<template #aside>
<b-img
thumbnail
rounded="circle"
src="https://picsum.photos/72/72/?image=58"
alt="Image"
></b-img>
</template>
<p class="mb-0">
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud
exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</p>
</b-media>
<b-overlay :show="show" no-wrap></b-overlay>
</b-card>
<b-button @click="show = !show" class="mt-3">Toggle overlay</b-button>
</div>
</template>
<script>
export default {
data() {
return {
show: true
}
}
}
</script>
When in no-wrap mode, <b-overlay> will not set the aria-busy attribute on the obscured element. You may also want to use an aria-live region in your app that announces to screen reader users that the page is busy.
Refer to the Accessibility section below for additional details and concerns.
Absolute vs fixed positioning for no-wrap
In cases where you want to obscure the entire app or page, when using the no-wrap prop, you can switch to viewport fixed positioning via setting the prop fixed on <b-overlay>. Note that this does not disable scrolling of the page, and note that any interactive elements on the page will still be in the document tab sequence.
You may also need to adjust the z-index of the overlay to ensure that the backdrop appears above all other page elements. Use the z-index property to override the default z-index value.
Refer to the Accessibility section below for additional details and concerns.
Overlay z-index
In some circumstances, you may need to adjust the z-index used by the overlay (depending on positioning in the DOM or the content being obscured). Simply set the z-index prop with a value suitable for your application or use case. The default z-index is 10.
Accessibility
Note that the overlay is visual only. You must disable any interactive elements (buttons, links, etc.) when the overlay is showing, otherwise the obscured elements will still be reachable via keyboard navigation (i.e. still in the document tab sequence).
If you have any links in the obscured content, we recommend using the <b-link> component, as it supports the disabled state, as native links (<a href="...">) and <router-link> components do not support the disabled state.
It is also recommended to add either the aria-hidden="true" or aria-busy="true" attribute to your obscured content when the overlay is visible. Just be careful not to add aria-hidden="true" to the wrapper that contains the <b-overlay> component (when using no-wrap), as that would hide any interactive content in the overlay slot for screen reader users.
If you are placing interactive content in the overlay slot, you should focus the content once the 'shown' event has been emitted. You can use the hidden event to trigger returning focus to an element as needed when the overlay is no longer visible.
When using the wrapping mode (prop no-wrap is not set), the wrapper will have the attribute aria-busy="true" set, to allow screen reader users to know that the wrapped content is in a busy or loading state. When prop no-wrap is set, the attribute will not be applied.
When using the no-wrap prop, and potentially the fixed prop, to obscure the entire application or page, you must ensure that all internative page elements (other than the content of the overlay) have been disabled and are not in the document tab sequence.
Use case examples
Here are just a few examples of common use cases of <b-overlay>. In all cases, we disable any interactive elements in the obscured area to prevent reachability via keyboard navigation (i.e. Tab key) or screen reader access.
Please refer to the Accessibility section for additional details and concerns.
Easily create a loading button:
<template>
<div>
<b-overlay
:show="busy"
rounded
opacity="0.6"
spinner-small
spinner-variant="primary"
class="d-inline-block"
@hidden="onHidden"
>
<b-button
ref="button"
:disabled="busy"
variant="primary"
@click="onClick"
>
Do something
</b-button>
</b-overlay>
</div>
</template>
<script>
export default {
data() {
return {
busy: false,
timeout: null
}
},
beforeDestroy() {
this.clearTimeout()
},
methods: {
clearTimeout() {
if (this.timeout) {
clearTimeout(this.timeout)
this.timeout = null
}
},
setTimeout(callback) {
this.clearTimeout()
this.timeout = setTimeout(() => {
this.clearTimeout()
callback()
}, 5000)
},
onHidden() {
this.$refs.button.focus()
},
onClick() {
this.busy = true
this.setTimeout(() => {
this.busy = false
})
}
}
}
</script>
In this example, we obscure the input and button:
<template>
<div>
<b-overlay :show="busy" rounded="lg" opacity="0.6" @hidden="onHidden">
<template #overlay>
<div class="d-flex align-items-center">
<b-spinner small type="grow" variant="secondary"></b-spinner>
<b-spinner type="grow" variant="dark"></b-spinner>
<b-spinner small type="grow" variant="secondary"></b-spinner>
<span class="sr-only">Please wait...</span>
</div>
</template>
<b-input-group size="lg" :aria-hidden="busy ? 'true' : null">
<b-form-input v-model="value" :disabled="busy"></b-form-input>
<b-input-group-append>
<b-button ref="button" :disabled="busy" variant="primary" @click="onClick">
Do something
</b-button>
</b-input-group-append>
</b-input-group>
</b-overlay>
</div>
</template>
<script>
export default {
data() {
return {
value: 'Some value',
busy: false,
timeout: null
}
},
beforeDestroy() {
this.clearTimeout()
},
methods: {
clearTimeout() {
if (this.timeout) {
clearTimeout(this.timeout)
this.timeout = null
}
},
setTimeout(callback) {
this.clearTimeout()
this.timeout = setTimeout(() => {
this.clearTimeout()
callback()
}, 5000)
},
onHidden() {
this.$refs.button.focus()
},
onClick() {
this.busy = true
this.setTimeout(() => {
this.busy = false
})
}
}
}
</script>
This example is a bit more complex, but shows the use of no-wrap, and using the overlay slot to present the user with a prompt dialog, and once confirmed it shows a uploading status indicator. This example also demonstrates additional accessibility markup.
<template>
<div>
<b-form class="position-relative p-3" @submit.prevent="onSubmit">
<b-form-group label="Name" label-for="form-name" label-cols-lg="2">
<b-input-group>
<b-input-group-prepend is-text>
<b-icon icon="person-fill"></b-icon>
</b-input-group-prepend>
<b-form-input id="form-name" :disabled="busy"></b-form-input>
</b-input-group>
</b-form-group>
<b-form-group label="Email" label-for="form-mail" label-cols-lg="2">
<b-input-group>
<b-input-group-prepend is-text>
<b-icon icon="envelope-fill"></b-icon>
</b-input-group-prepend>
<b-form-input id="form-email" type="email" :disabled="busy"></b-form-input>
</b-input-group>
</b-form-group>
<b-form-group label="Image" label-for="form-image" label-cols-lg="2">
<b-input-group>
<b-input-group-prepend is-text>
<b-icon icon="image-fill"></b-icon>
</b-input-group-prepend>
<b-form-file id="form-image" :disabled="busy" accept="image/*"></b-form-file>
</b-input-group>
</b-form-group>
<div class="d-flex justify-content-center">
<b-button ref="submit" type="submit" :disabled="busy">Submit</b-button>
</div>
<b-overlay :show="busy" no-wrap @shown="onShown" @hidden="onHidden">
<template #overlay>
<div v-if="processing" class="text-center p-4 bg-primary text-light rounded">
<b-icon icon="cloud-upload" font-scale="4"></b-icon>
<div class="mb-3">Processing...</div>
<b-progress
min="1"
max="20"
:value="counter"
variant="success"
height="3px"
class="mx-n4 rounded-0"
></b-progress>
</div>
<div
v-else
ref="dialog"
tabindex="-1"
role="dialog"
aria-modal="false"
aria-labelledby="form-confirm-label"
class="text-center p-3"
>
<p><strong id="form-confirm-label">Are you sure?</strong></p>
<div class="d-flex">
<b-button variant="outline-danger" class="mr-3" @click="onCancel">
Cancel
</b-button>
<b-button variant="outline-success" @click="onOK">OK</b-button>
</div>
</div>
</template>
</b-overlay>
</b-form>
</div>
</template>
<script>
export default {
data() {
return {
busy: false,
processing: false,
counter: 1,
interval: null
}
},
beforeDestroy() {
this.clearInterval()
},
methods: {
clearInterval() {
if (this.interval) {
clearInterval(this.interval)
this.interval = null
}
},
onShown() {
this.$refs.dialog.focus()
},
onHidden() {
this.$refs.submit.focus()
},
onSubmit() {
this.processing = false
this.busy = true
},
onCancel() {
this.busy = false
},
onOK() {
this.counter = 1
this.processing = true
this.clearInterval()
this.interval = setInterval(() => {
if (this.counter < 20) {
this.counter = this.counter + 1
} else {
this.clearInterval()
this.$nextTick(() => {
this.busy = this.processing = false
})
}
}, 350)
}
}
}
</script>
Using in <b-modal>
The modal body has position: relative; set, so when using <b-overlay no-wrap ...> in the modal body only the modal body will be obscured. If you wish to obscure the entire modal (including the header and footer), you will need to set the <b-modal> prop body-class to position-static, and also set the rounded prop on <b-overlay>.