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Panel Documentation has not yet been reviewed by a human.

Panel is a container that can maximize to the browser viewport without moving or remounting its children. It fills its parent’s width and height and uses overflow: auto to show scrollbars only when content overflows.

Give the parent a defined height for Panel to fill vertically. With an auto-height parent, percentage height follows normal CSS sizing and the Panel can grow with its content. A parent’s min-height alone does not generally establish a height for height: 100% to fill.

Warning: For now, Panel is a nonvisual utility container only. Supply your own appearance and controls. Built-in chrome, resizing, and folding are not available yet.

Usage

Declarative

Panel manages its own state. Use data-custom-event="paneltoggle" on an Anta button to toggle maximization without a click handler.

Maximize / restore

import { Box, Button, Input, Panel } from '@antadesign/anta'

function Workspace() {
  return (
    <Panel style={{ background: 'var(--bg-3)' }}>
      <Box
        display="flex"
        gap={16}
        padding={16}
      >
        <Input aria-label="Workspace note" placeholder="Write a note" />
        <Button data-custom-event="paneltoggle">
          Maximize / restore
        </Button>
      </Box>
    </Panel>
  )
}

Controlled

Pass maximized to manage state in your application. The button updates it through onClick; onStateChange accepts requests from declarative controls inside the panel.

Maximize panel

import { useState } from 'react'
import { Box, Button, Input, Panel } from '@antadesign/anta'

function Workspace() {
  const [maximized, setMaximized] = useState(false)

  return (
    <Panel
      style={{ background: 'var(--bg-3)' }}
      maximized={maximized}
      onStateChange={(_event, { next }) => setMaximized(next)}
    >
      <Box
        display="flex"
        gap={16}
        padding={16}
      >
        <Input aria-label="Workspace note" placeholder="Write a note" />
        <Button onClick={() => setMaximized(value => !value)}>
          {maximized ? 'Restore panel' : 'Maximize panel'}
        </Button>
      </Box>
    </Panel>
  )
}

How does this work?

Maximizing applies popover="manual" to the internal content slot and calls showPopover() to fill the viewport. Children keep their DOM ancestry, theme, and event bubbling. A placeholder preserves the panel’s normal layout size. Restoring calls hidePopover() and returns the same content to normal layout.

<!-- Managed by Panel inside its shadow root. -->
<slot part="content" popover="manual" tabindex="-1"></slot>

While maximized, Panel traps focus inside its content. Tab and Shift+Tab cycle through its controls. Restoring releases the trap and returns focus to the previous external control, when available.

Provide a keyboard-accessible Restore control: Escape and outside clicks do not restore the panel. Panel adds no dialog role or background inertness. Maximizing Panel does not lock page scrolling; the page’s viewport scrollbar may remain visible and usable. Use Dialog for modal interactions.

Panel fills the browser viewport, without invoking the Fullscreen API. Browsers without Popover API support keep it in normal layout.

Component props

For uncontrolled state, omit maximized and optionally set defaultMaximized. Call event.preventDefault() synchronously in onStateChange to cancel an uncontrolled transition. In controlled mode, reject a request by leaving maximized unchanged.

Prop	Type	Default	Description
maximized?	boolean	—	Fill the browser viewport and contain keyboard focus within the panel. When supplied, the application owns the state.
defaultMaximized?	boolean	—	Initial viewport maximization for an uncontrolled panel, read once on connect.
onStateChange?	(event, detail) => void	—	Requested maximization change. Update `maximized` to accept a controlled request, or prevent the event to veto an uncontrolled request.

Inherited props (children, className, id, slot, style, tabIndex, title)

Prop	Type	Default	Description
children?	ReactNode	—	Child elements. When provided, replaces the component's default label/content.
className?	string	—	CSS class on the component's root element (merged with the component's own classes). Use it directly for layout and positioning — grid/flex placement, margins, alignment — rather than wrapping the component in a `<div>`/`<span>`.
id?	string	—	HTML `id` attribute.
slot?	string	—	Assigns the element to a named `<slot>` of a parent web component (e.g. `slot="header"` inside a `<Dialog>`, `slot="footer"` inside a `<Dialog>`).
style?	CSSProperties	—	Inline styles on the component's root element. Set layout/positioning here (or via `className`) directly on the component instead of adding a wrapper.
tabIndex?	number	—	Tab order. Set to `-1` to skip the element when tabbing.
title?	string	—	HTML `title` attribute — native browser tooltip on hover.

Plus every standard DOM event handler (onClick, onFocus, onKeyDown, …) and any data-* or aria-* attribute — forwarded as-is to the underlying <a-*> element.

Web component

Import @antadesign/anta/elements to register the elements in this example. The button toggles the nearest panel without JavaScript handlers.

Maximize / restore

<a-panel style="background: var(--bg-3)">
  <a-box display="flex" padding="16px" gap="16px" style="--box-padding: 16px; --box-gap: 16px">
    <a-input aria-label="Workspace note" placeholder="Write a note"></a-input>
    <a-button role="button" tabindex="0" data-custom-event="paneltoggle">
      Maximize / restore
    </a-button>
  </a-box>
</a-panel>

Use state="normal" or state="maximized" for controlled state, or default-state="maximized" for an initially maximized, uncontrolled panel.

requestMaximize() and requestRestore() emit a cancelable, non-bubbling statechange with { next, prev } using those state strings. Anta buttons can send panelmaximizerequest, panelrestorerequest, or paneltoggle through data-custom-event to the nearest Panel.

Styling

Panel defaults to display: block, width: 100%, height: 100%, box-sizing: border-box, and overflow: auto. Padding and borders stay inside its assigned size. It does not set flex-grow.

Override these through ordinary CSS. Use height: auto for content-driven height or overflow: scroll to request scrollbars even when content fits. Scrollbar appearance follows the browser and operating system’s settings.

Set the background on Panel. Its maximized surface inherits that background, so inner content can keep its natural height. Style light-DOM children, such as Box or Capture, for content layout shared between both states. Use :state(maximized) for viewport styling and ::part(content) for the maximized scrolling surface. In normal mode, the content slot uses display: contents. The maximized surface also uses overflow: auto; override ::part(content) to change its overflow separately from the normal Panel.

The ::part(placeholder) region reserves the normal content size while the surface is maximized. Panel measures its width and height, but your ::part() rules can override those dimensions. Changing layout properties such as width, height, padding, border, or box-sizing can change the reserved space and move neighboring content. To preserve that space, customize background or outline and leave layout properties unchanged.

Use ::part(content)::backdrop to style the native popover backdrop. By default, the backdrop is transparent and ignores pointer events.

Defaults live in external CSS and follow Anta’s cascade layers. Put normal part overrides in components, utilities, or unlayered CSS. A base layer rule no longer overrides these defaults. See Content Security Policy for stylesheet loading and inline-style constraints.

Inside another shadow root, load @antadesign/anta/elements/a-panel.css in that root through a stylesheet link. Document styles cannot reach Panel there.

Enter a note, then select Maximize panel and Restore panel. The input keeps its value. The panel-demo classes supply this example’s appearance; replace them with your own selectors.

Panel keeps this Box and Capture in their original DOM location.

<a-panel class="panel-demo">
  <a-box class="panel-demo-content">
    <a-box class="panel-demo-toolbar" display="flex">
      <a-text weight="medium">Workspace preview</a-text>
      <a-button role="button" tabindex="0" data-custom-event="paneltoggle">
        <span class="panel-demo-maximize">Maximize panel</span>
        <span class="panel-demo-restore">Restore panel</span>
      </a-button>
    </a-box>
    <a-capture>
      <a-input placeholder="Write a note before maximizing" aria-label="Workspace note"></a-input>
      <a-text>Panel keeps this Box and Capture in their original DOM location.</a-text>
    </a-capture>
  </a-box>
</a-panel>

.panel-demo { border: 1px solid var(--border-4); border-radius: 8px; background: var(--bg-3); }
.panel-demo-content { display: flex; flex-direction: column; gap: 20px; padding: 20px; }
.panel-demo-toolbar { justify-content: space-between; align-items: center; gap: 12px; flex-wrap: wrap; }
.panel-demo-content a-capture { display: grid; gap: 16px; }
.panel-demo-content a-input { width: 100%; }
.panel-demo-restore { display: none; }
.panel-demo:state(maximized) .panel-demo-content { padding: max(20px, env(safe-area-inset-top)) max(20px, env(safe-area-inset-right)) max(20px, env(safe-area-inset-bottom)) max(20px, env(safe-area-inset-left)); }
.panel-demo:state(maximized) .panel-demo-maximize { display: none; }
.panel-demo:state(maximized) .panel-demo-restore { display: inline; }

Panel ✦Documentation has not yet been reviewed by a human.