# Detachable panes (`window.feedBack.panes`)

Pop a panel out of the app into its own OS window, and leave it there: while you
play, across song switches, on a second monitor, minimized to the system tray.

Panes exist because the player's rail popovers are **exclusive** — opening one
closes the last. You cannot watch the mixer while riding the camera, and both
vanish the moment you want to look at the highway.

---

## The whole idea, in one sentence

**We move the real element.**

Not a copy of your panel. Not a re-implementation of it in the pop-out window.
The actual DOM node. Same-origin windows can adopt each other's nodes, and an
adopted node keeps its event listeners and its closures — so your panel goes on
running *your* code, against *your* state, in *your* realm. The app's stylesheets
are copied into the pane window, so it looks identical too.

What you popped out is what you get. That is the promise, and it is the reason
there is no `ctx`, no state mirroring, no cross-window RPC and no second copy of
your UI to keep in step with the first. Those are all solutions to a problem we
simply do not have.

---

## Adding a pane to your plugin

Two lines.

```js
// Guard: the panes API is optional. On a host without it, skip both calls and
// your panel behaves exactly as it does today.
const panes = window.feedBack && window.feedBack.panes;
if (panes && typeof panes.register === 'function') {
    panes.register({
        id: 'camera_director',
        title: 'Camera Director',
        icon: '🎥',
        element: () => panelEl,      // your existing panel, as it is
    });
    panes.attachChip(panelEl, 'camera_director');
}
```

`attachChip()` injects **the** standard pop-out chip (`⇱`) — same glyph, same
place, same behaviour in every plugin. Clicking it moves your panel into a window
and leaves a "⇲ … is popped out" stub in its place; clicking the stub brings it
back, to exactly the spot it left. Core owns the chip, the hiding and the stub, so
you write no show/hide logic.

That's it. Your sliders, your presets, your tabs, your CSS, your event handlers,
your state — all of it comes along, because none of it moved anywhere except into
a different window's document.

### `element` is a function for a reason

It is resolved at open time, not at registration. Plugins commonly build their
panel lazily on first use, or rebuild it wholesale when something changes (Camera
Director rebuilds its panel on every mode change). Asking for it when we need it
means we always move the live one.

**If you rebuild your panel, re-attach the chip.** Rebuilding takes the chip with
it. `attachChip()` returns a `detach()`; call it before re-attaching, and again in
your teardown — otherwise you leave a stub pointing at DOM that no longer exists.

```js
if (chipDetach) chipDetach();
chipDetach = panes.attachChip(panel, PANE_ID, { header: toolsEl });
```

Re-attaching is safe while the pane is popped out: the chip reconciles against the
pane's real state, so a panel rebuilt mid-pop-out stays correctly stubbed.

### The one thing core changes about your element

`.fb-paned` is added while the pane is out, and it neutralises **placement only**:

```css
position: static; inset: auto; width: 100%;
max-width: none; max-height: none; z-index: auto; box-shadow: none;
```

Your panel was almost certainly a fixed overlay pinned to a corner of the app
(`position:fixed; top:72px; right:18px; width:288px`). Alone in its own window,
every one of those is wrong — it would float 72px down from the top of a 380px
window, still 288px wide, still casting a shadow over nothing. Colours, borders,
radius, padding, fonts and your panel's own internal layout are untouched.

The class is removed the moment the element goes home.

---

## Spec

```js
feedBack.panes.register({
    id,                    // required, unique
    element,               // required — an Element, or a function returning one
    title,                 // shown in the pane window's title bar, the dock card, the tray
    icon,                  // one glyph, for the dock/tray/launcher lists
    width, height,         // the pane window's initial size (it remembers yours after that)
    defaultHost,           // 'window' (default) or 'dock'
    onHost,                // optional (hostId | null, el) => void — re-measure/re-anchor
});
```

```js
feedBack.panes.attachChip(el, paneId, { header })   // → detach()
feedBack.panes.open(id, { host }) / close(id) / detach(id) / dock(id) / focus(id)
feedBack.panes.isOpen(id) / hostOf(id) / get(id) / list()
```

`attachChip` puts the chip in `el.querySelector('[data-pane-header]')` if it finds
one, or in the `header` element you pass, or at the top of `el` otherwise.

---

## Hosts

`detach(id)` puts a pane in the best host available:

| host | | |
|---|---|---|
| `window` | 10 | A real OS window. In the desktop app: remembered bounds, always-on-top, system tray. |
| `dock` | 0 | A card in the in-window stack. **The floor** — always available, so opening a pane can never fail. |

You don't pick; you declare `defaultHost` and the router does the rest.

In the **desktop app** a pane you left popped out comes back popped out on next
launch. In a **browser** it comes back **docked** — a browser blocks
`window.open()` without a user gesture, so restoring it would only ever produce a
"pop-up blocked" toast. The chip pops it out again on your next click.

---

## Things worth knowing

1. **Your code still runs in the main window.** The element is displayed in the
   pane window, but its closures, its timers and its `document` references all
   still belong to the main realm. That is exactly why everything keeps working —
   but it means a `document.body.appendChild()` inside your panel (a tooltip, a
   popover) lands in the **main** window, not the pane. Anchor such things to the
   panel itself, not to `document.body`.

2. **Chromium throttles a backgrounded window's `requestAnimationFrame`.** While
   the user is looking at your pane, the main window may be in the background —
   and your rAF lives there. Event-driven panels (sliders, buttons, presets) are
   unaffected. A panel that *animates* continuously may run slowly while it's the
   only thing you're looking at.

3. **The element goes home exactly where it came from** — same parent, same
   position among its siblings. Don't move it yourself while it's popped out.

4. **A pane the user closed with the window's X button is reaped** (a crashed
   renderer never gets to say goodbye), and your element is docked back. Without
   that, your panel would be stranded in a dead document with no way back.

5. **Nothing here is required.** On a host without the panes API, `feedBack.panes`
   is undefined, you skip both calls, and your panel behaves exactly as it does
   today.