shared/dropdown: optional portal mode escapes a scroll-container clip

A `WantedMenu` badge dropdown on the agents table clips against
`.ui-table-scroll`s overflow the moment its row is the last (or
near-last) one — the popover extends past the table content the
scroll container bounds itself to. `Table.tsx` already solved the
identical clip for its own column-filter popover with a
position:fixed + portal computed from the anchor rect; `Dropdown` now
takes an optional `portal` prop that opts a caller into that same
recipe instead of a second hand-rolled copy of it. Off by default —
every other current caller (StatusChips x2, the components-page demo)
keeps its existing non-portal behavior unchanged.
This commit is contained in:
iris 2026-09-11 21:20:12 +02:00
commit 613ca541e1
2 changed files with 63 additions and 8 deletions

View file

@ -9,12 +9,23 @@
// for free, so this hand-rolls the same "outside click or Escape
// closes" contract `Dialog` gets from the platform.
//
// Positioning is the caller's job: render `<Dropdown>` as a child of a
// `position: relative` wrapper (the badge + dropdown pair) and it anchors
// to that box's bottom-left via CSS. No portal — a badge in a normal
// document-flow header never needs one, and skipping it keeps focus
// management simple (no re-parenting to `<body>` to reason about).
import { useEffect, useRef } from "preact/hooks";
// Positioning is the caller's job by default: render `<Dropdown>` as a
// child of a `position: relative` wrapper (the badge + dropdown pair)
// and it anchors to that box's bottom-left via CSS — no portal, no
// re-parenting to `<body>` to reason about. That's wrong the moment the
// wrapper sits inside a scrolling container, though: an ancestor with
// `overflow-x: auto` computes `overflow-y` to `auto` too (per the CSS
// overflow spec), so it clips the dropdown vertically the instant the
// container is shorter than header-plus-dropdown — reported against
// swarm-ui's agent table (a `WantedMenu` badge two rows from the
// bottom). `../../ui/table/Table.tsx` hit the identical clip for its
// own column-filter popover and fixed it with `position: fixed`
// computed from the anchor's `getBoundingClientRect()`, rendered via a
// portal outside the scrolling subtree; the optional `portal` prop
// below opts a caller into that same recipe instead of a second
// hand-rolled copy of it.
import { useEffect, useRef, useState } from "preact/hooks";
import { createPortal } from "preact/compat";
import type { ComponentChildren, RefObject } from "preact";
import "./Dropdown.css";
@ -51,6 +62,13 @@ export interface DropdownProps {
* one ref) already avoids this.
*/
anchorRef?: RefObject<HTMLElement>;
/**
* Escape a clipping scroll ancestor by portal-rendering to `<body>`
* with `position: fixed`, computed from `anchorRef`'s rect see the
* file-top comment. Requires `anchorRef`; a caller in an unscrolled,
* un-clipped context (the common case) can omit this entirely.
*/
portal?: boolean;
}
export function Dropdown({
@ -61,8 +79,13 @@ export function Dropdown({
onClose,
label,
anchorRef,
portal,
}: DropdownProps) {
const ref = useRef<HTMLDivElement>(null);
// Only populated (and only consulted) in `portal` mode — see the
// effect below and the file-top comment for why fixed-position
// coordinates are needed at all here.
const [pos, setPos] = useState<{ top: number; left: number } | null>(null);
useEffect(() => {
if (!open) return;
@ -86,10 +109,35 @@ export function Dropdown({
};
}, [open, onClose]);
// Same recipe as `Table.tsx`'s column-filter popover: compute once on
// open, then keep it pinned to the anchor across any scroll in the
// tree (`capture: true` sees a nested scroll container too, since
// plain `scroll` doesn't bubble) or a viewport resize.
useEffect(() => {
if (!open || !portal) return;
function recompute() {
const rect = anchorRef?.current?.getBoundingClientRect();
if (rect) setPos({ top: rect.bottom + 4, left: rect.left });
}
recompute();
window.addEventListener("scroll", recompute, true);
window.addEventListener("resize", recompute);
return () => {
window.removeEventListener("scroll", recompute, true);
window.removeEventListener("resize", recompute);
};
}, [open, portal, anchorRef]);
if (!open) return null;
return (
<div class="ui-dropdown" role="menu" aria-label={label} ref={ref}>
const list = (
<div
class="ui-dropdown"
role="menu"
aria-label={label}
ref={ref}
style={portal && pos ? { position: "fixed", ...pos } : undefined}
>
{options.map((opt) => (
<button
type="button"
@ -111,4 +159,10 @@ export function Dropdown({
))}
</div>
);
// Not yet positioned (first render after opening, before the effect
// above runs) — skip the portal render entirely rather than flashing
// the list at `document.body`'s origin for one frame.
if (portal) return pos ? createPortal(list, document.body) : null;
return list;
}

View file

@ -213,6 +213,7 @@ function WantedMenu({
/>
<Dropdown
open={open}
portal
options={options}
activeValue={row.wanted ?? undefined}
label={`declare ${row.name}`}