Popover

Popover component that reveals a floating bubble card layer when the trigger is hovered or clicked.

Use when you need a floating bubble panel that opens on hover or click of a trigger. <r-popover> positions and portals its <r-content> panel and wires the accessibility for you.

Quick Start

Basic Usage

The trigger lives in the default slot; the floating content is wrapped in a nested <r-content> element.

<r-popover style="display: inline-block;">
  <r-button>popover</r-button>
  <r-content>
    <div>this is content</div>
  </r-content>
</r-popover>

API Reference

Properties

Trigger Mode trigger

<r-popover trigger="hover" style="display: inline-block;">
  <r-button>hover</r-button>
  <r-content>
    <div>hover</div>
  </r-content>
</r-popover>

<r-popover trigger="click" style="display: inline-block;">
  <r-button>click</r-button>
  <r-content>
    <div>click</div>
  </r-content>
</r-popover>

Placement placement

<r-popover trigger="hover" placement="top" style="display: inline-block;">
  <r-button>top</r-button>
  <r-content>
    <div>top</div>
  </r-content>
</r-popover>

<r-popover trigger="hover" placement="bottom" style="display: inline-block;">
  <r-button>bottom</r-button>
  <r-content>
    <div>bottom</div>
  </r-content>
</r-popover>

<r-popover trigger="hover" placement="left" style="display: inline-block;">
  <r-button>left</r-button>
  <r-content>
    <div>left</div>
  </r-content>
</r-popover>

<r-popover trigger="hover" placement="right" style="display: inline-block;">
  <r-button>right</r-button>
  <r-content>
    <div>right</div>
  </r-content>
</r-popover>

Alignment placement="<side>-<align>"

A bare side lines the panel's leading edge up with the trigger's. Add -center or -end when it should sit centred on the trigger, or flush with the trigger's trailing edge instead, useful for a menu anchored to the right end of a header bar, so that it opens inwards rather than being pushed back inside the viewport by the shift. The suffix survives an auto-flip: bottom-end becomes top-end, not top.

<r-popover trigger="hover" placement="bottom-end" style="display: inline-block;">
  <r-button>bottom-end</r-button>
  <r-content>
    <div style="width: 200px;">bottom-end</div>
  </r-content>
</r-popover>

Slots

Both components expose a single unnamed default slot; there are no named slots.

Open State open

open is the panel's state, reflected as an attribute the way <details open> and <dialog open> are. Nothing infers it from the panel's display, which trails the state by the length of the exit animation, so the attribute, aria-expanded and what is on screen cannot disagree.

<r-popover id="pop" trigger="click">
  <r-button>Trigger</r-button>
  <r-content><div>Content</div></r-content>
</r-popover>

<script>
  const pop = document.getElementById('pop');
  pop.open = true; // or pop.show()
  pop.open = false; // or pop.hide()
  pop.toggle();
</script>

show(), hide() and toggle() are thin wrappers over it. closePopover() remains as an alias for hide().

Events

<r-popover> fires four events around the panel's transitions, none of which carry a detail:

The wait is the stylesheet's own animation rather than a duration copied into script, so under prefers-reduced-motion (where there is no animation to play), after-hide follows hide immediately instead of after a fixed delay.

It is otherwise driven by standard DOM interaction:

• Open: mouseenter (when trigger includes hover), click, or pressing Enter / Space while focused.
• Close: mouseleave (hover mode), pressing Escape, or a click elsewhere in the document.

Escape also works from interactive content in the portaled panel and returns focus to its opening trigger. A nested popup handles its own Escape first; an already handled Escape or IME composition does not dismiss the parent. An immediate close cancels queued entrance work, including before the first painted frame. Tab order and modal focus trapping remain the composed interface's responsibility; a popover is not a modal dialog.

Internally, the companion <r-content> element watches its own subtree with a MutationObserver and emits a change CustomEvent (detail: { type, value: { content, mutation } }) that the popover consumes to keep the panel in sync. This is an implementation detail rather than a public API.

Accessibility is wired automatically: the host receives tabindex="0", aria-haspopup="dialog", and an aria-expanded that toggles between "false" and "true" as the panel opens and closes.

Best Practices

• Trigger element: Place a focusable control (e.g. <r-button>) as the trigger so keyboard open/close works.
• Content wrapper: Always wrap panel content in <r-content>: plain children that are not inside <r-content> are not shown as the floating panel.
• Inline sizing: The host is display: block; add style="display: inline-block;" (or place it in an inline context) so it shrinks to the trigger.
• Placement: placement is a preference, not a guarantee: when the trigger is near a viewport edge and the preferred side lacks room, the panel automatically flips to the opposite side and shifts along the cross axis to stay on-screen. This auto-flip only applies to the default body-level positioning.
• Scoped container: Use getPopupContainerId to anchor the panel inside a specific scroll/positioning container when the default body-level positioning is not desired. Flip/shift do not apply in this mode, so choose a placement that fits the container. The alignment suffix does apply there, exactly as it does in the body portal.