docs(panes): best practices for plugin authors

Every rule here is something that has already gone wrong on this feature —
mostly in core's own code, twice in the two plugins that adopted it first.
They are cheap to get right up front and miserable to diagnose later,
because a broken pane almost always LOOKS perfect.

The traps, and why each one is easy to walk into:

- Your code still runs in the main window. That is exactly why moving the
  element works at all — and exactly why `document.body.appendChild(tooltip)`
  inside a popped-out panel lands in the window the user is NOT looking at.

- Don't hide your own panel when it pops out. Core hides it and leaves a
  stub. A plugin that also hides it hides the node that just moved — which is
  precisely how core's own chip shipped a blank pop-out window.

- Use `hidden` or a class, not inline `display`, for show/hide. `.fb-paned`
  forces the panel visible while it is out; when it docks and that class is
  removed, an inline `display:none` reasserts itself and the panel returns
  invisible.

- `isConnected` does not mean "docked". A panel in a pane window IS connected,
  just not to this document. The test you meant is
  `el.ownerDocument === document`.

- `element` is a function so it can be resolved late: return the LIVE node, and
  re-attach the chip if you rebuild your panel (Camera Director rebuilds on
  every mode change).

- rAF is throttled while the main window is backgrounded — which it is, whenever
  the user is looking at your pane. Event-driven panels don't care; continuously
  animating ones will stutter exactly when they are the only thing on screen.

- Don't synchronise anything. One realm, one panel. Writing sync code means
  you have misunderstood the model.

Also states what core guarantees back, including the one that cost the most to
learn: the element is evacuated BEFORE the pane window's document is destroyed,
so it comes home alive rather than as a photograph of a panel with every
listener in its subtree silently gone.

Signed-off-by: topkoa <topkoa@gmail.com>
This commit is contained in:
topkoa 2026-07-12 18:49:56 -04:00
parent 503716acbf
commit 67e6b25c43
2 changed files with 141 additions and 20 deletions

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@ -465,6 +465,40 @@ window.feedBack.diagnostics.contribute('my_plugin', {
Loaded from `static/diagnostics.js` ASAP in `<head>` so the console-wrap is in place before any other script runs. Available on the `window.feedBack.diagnostics` namespace alongside `snapshotConsole()`, `snapshotHardware()`, `snapshotUa()`, `snapshotLocalStorage()`, `snapshotContributions()`. Keep your payload small (< 100 KB) and don't include secrets bundles are shared with maintainers.
### Detachable panes — pop your panel out into its own window
If your plugin has a floating panel that sits over the player — a mixer, a camera rig, a settings board — you can let the user pop it out into its own OS window and leave it there: while they play, across song switches, on a second monitor, minimized to the tray. Two calls:
```js
feedBack.panes.register({
id: 'camera_director',
title: 'Camera Director',
icon: '🎥',
element: () => panelEl, // your existing panel, exactly as it is
});
feedBack.panes.attachChip(panelEl, 'camera_director');
```
**The host moves your real element.** Not a copy, not a re-render — the actual DOM node, adopted into the pop-out window, keeping its listeners and its closures. Your panel goes on running *your* code against *your* state. It looks and behaves like what was popped out because it **is** what was popped out. Nothing to mirror, nothing to keep in sync.
The rules below are all things that have already gone wrong. Full contract: **[docs/plugin-panes.md](docs/plugin-panes.md)**.
- **Your code still runs in the main window.** The element is *displayed* elsewhere; its closures, timers and `document` references still belong to the main realm. That is exactly why everything keeps working — and exactly why `document.body.appendChild(myPopover)` lands in the **main window, not the pane**. Anchor tooltips, popovers and menus to your panel, not to `document.body`. Measure with `el.ownerDocument.defaultView`, never a cached `window`.
- **Don't hide your panel yourself when it pops out.** Core hides it and leaves a "bring it back" stub. If you also hide it, you will hide the node that just moved — and blank the pane window.
- **Prefer `hidden` or a class over inline `display` for show/hide.** While popped out, core neutralises *placement* with `.fb-paned` (`position`, `inset`, `width`, `z-index`, `box-shadow`). An inline `display:none` on your panel reasserts itself the moment the pane docks back and the class is removed, so your panel returns invisible.
- **`element` is a function so it can be resolved late.** Return the *live* node. If you rebuild your panel (Camera Director rebuilds on every mode change), re-run `attachChip` — it returns a `detach()`; call it before re-attaching, and again in your teardown.
- **`isConnected` does not mean "docked".** A panel sitting in a pane window is very much connected — just not to *this* document. Test `el.ownerDocument === document`, or take the `onHost(hostId, el)` callback.
- **rAF is throttled while the main window is backgrounded** — and it will be, whenever the user is looking at your pane. Event-driven panels (sliders, buttons) are unaffected. A panel that *animates continuously* may run slowly while it is the only thing on screen.
- **Don't reach for BroadcastChannel, `postMessage`, or a second copy of your state.** There is one realm and one panel. If you find yourself synchronising, you have misunderstood the model.
- **Nothing is required.** No panes API on the host → skip both calls, and your panel behaves exactly as it does today.
### Keyboard Shortcuts
Plugins can register keyboard shortcuts via the global `window.registerShortcut()` function. Shortcuts appear in the `?` help panel.

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@ -153,28 +153,115 @@ launch. In a **browser** it comes back **docked** — a browser blocks
---
## Things worth knowing
## Best practices
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`.
Every item below is something that has already gone wrong, in this codebase, on
this feature. They are cheap to get right up front and confusing to diagnose later
— a broken pane usually *looks* perfect.
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.
### 1. Your code still runs in the main window
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.
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 precisely why
everything keeps working** — and it has one sharp consequence:
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.
```js
// WRONG — lands in the MAIN window, not the pane the user is looking at.
document.body.appendChild(myTooltip);
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.
// RIGHT — anchored to the panel, so it travels with it.
panelEl.appendChild(myTooltip);
```
Same for measuring. `window.innerWidth` is the *main* window's. Use
`el.ownerDocument.defaultView` when you need the window your panel is actually in.
### 2. Don't hide your panel yourself
Core hides it and leaves a "bring it back" stub. If your plugin *also* hides it,
you are hiding the node that just moved — and the pane window renders nothing.
(This is not hypothetical: core's own chip did exactly this, and the first
pop-out shipped blank because of it.)
### 3. Prefer `hidden` or a class for show/hide
Core makes your panel visible while it's hosted — it clears `hidden`, and clears an
inline `display: none` if that's how you hide — and **restores both on dock**. So
either style works.
`hidden` is still the better choice: it composes with everything, and it leaves
your panel's `display` mode (`flex`, `grid`, whatever it is) entirely alone. Core
deliberately does not override `display` for exactly that reason.
```js
panel.hidden = true; // best
panel.style.display = 'none'; // works — core saves and restores it
```
### 4. `element` is a function — return the *live* node
It is resolved when the pane opens, not when you register. Plugins build panels
lazily, and rebuild them wholesale (Camera Director rebuilds on every mode
change). If you rebuild yours, **re-attach the chip**:
```js
if (chipDetach) chipDetach(); // attachChip returns a detach()
chipDetach = feedBack.panes.attachChip(panel, PANE_ID, { header: toolsEl });
```
Call `chipDetach()` in your teardown too, or you leave a stub pointing at DOM that
no longer exists.
### 5. `isConnected` does not mean "docked"
A panel sitting in a pane window is **connected** — just not to *this* document.
Code that asks "am I still mounted?" with `isConnected` will get `true` and act on
a panel that is somewhere else entirely.
```js
const docked = el.ownerDocument === document; // this is the question you meant
```
Or take the optional `onHost(hostId, el)` callback, which fires on both moves.
### 6. Expect rAF to be throttled while your pane has focus
Chromium throttles a **backgrounded** window's `requestAnimationFrame` — and the
main window is exactly what's backgrounded while the user is looking at your pane.
Your rAF lives in the main window.
Event-driven panels (sliders, buttons, presets) don't care. A panel that
*animates continuously* may run slowly precisely when it's the only thing on
screen. Drive such animation from data you already have, or accept the stutter.
### 7. Don't synchronise anything
No `BroadcastChannel`, no `postMessage`, no second copy of your state, no mirrored
UI. There is **one** realm and **one** panel. If you find yourself writing sync
code, you have misunderstood the model — the whole point is that there is nothing
to sync.
### 8. Nothing here is required
On a host without the panes API, `feedBack.panes` is `undefined`. Skip both calls
and your panel behaves exactly as it does today. Guard, don't depend:
```js
const panes = window.feedBack && window.feedBack.panes;
if (!panes || typeof panes.register !== 'function') return;
```
---
## Things core guarantees
- **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.
- **It comes home alive.** Core evacuates the element *before* the pane window's
document is destroyed. (Get this wrong — dock after the window dies — and the
node returns looking perfect with every listener in its subtree silently gone.
That bug is why this section exists.)
- **A pane window the user closes, or that crashes, is reaped** and the element
docked back. Your panel is never stranded in a dead document.
- **The app's stylesheets are copied into the pane window**, so your panel looks
identical — including your plugin's own `styles` sheet.