- The popped-out window is a `QWidget` with `Qt::Window | Qt::FramelessWindowHint`
  (or a thin custom frame).
- Custom drag handle at top: click-drag moves the window, ↙ button re-docks,
  ✕ closes (which should pop-in, not destroy the panadapter).
- The `SpectrumWidget` (or Radio Panel widget) is **re-parented**, not cloned —
  the same live widget moves into the floating window. No duplication of VITA-49
  routing or signal connections needed.

### Main window while panel is popped out

- The vacated slot in the `PanadapterStack` QSplitter collapses to zero height
  (or shows a thin placeholder strip with the pan name and a ↗ "re-open"
  button).
- The main window remains fully functional for all other panels.

### Pop-in (re-docking)

- Clicking ↙ in the floating window re-parents the widget back into the
  `PanadapterStack` at its original index.
- The placeholder strip in the main window expands back to the previous size.
- If the original slot no longer exists (pan was deleted while floating), the
  widget is destroyed gracefully.

### Persistence (`AppSettings`)

On launch, AetherSDR restores floating state before the first paint so there
is no visible "snap" of windows jumping around.

### Radio Panel pop-out

The same mechanism applies to the Radio Panel (the `MainWindow` center pane
containing `VfoWidget`, mode selector, `AppletPanel`, etc.). This lets the
operator move the entire control surface to a secondary monitor while the
spectrum stays on the primary.

## Protocol Hints

No FlexLib/SmartSDR protocol involvement — this is **purely a client-side
Qt windowing feature**. The radio is unaware of window positions.

The relevant Qt classes are:

| Class | Role |
|-------|------|
| `QWidget::setParent(nullptr)` + `show()` | Re-parent widget as top-level window |
| `QWidget::setParent(container)` + `show()` | Re-parent widget back into layout |
| `Qt::Window \| Qt::FramelessWindowHint` | Create borderless floating window |
| `QSplitter` | Already used in `PanadapterStack` — handles collapse on re-parent |
| `AppSettings` | Persist geometry and floating state |

> ⚠️ **Re-parenting caveat:** Qt re-parenting destroys and re-creates the
> native window handle. On X11/Wayland, OpenGL contexts (if any) must be
> re-initialized. `SpectrumWidget` currently uses `QPainter`/`QPixmap` — no
> OpenGL — so re-parenting should be safe. Verify this assumption before
> implementing.

> ⚠️ **Wayland note:** `Qt::FramelessWindowHint` behaves differently under
> Wayland compositors; window positioning via `move()` may be ignored. May
> need `QWindow::setPosition()` workaround or fallback to decorated windows
> on Wayland. Test on both X11 and Wayland (KDE/GNOME).

## Implementation Sketch

```cpp
// PanadapterApplet.h — add pop-out support
class PanadapterApplet : public QWidget {
    // ...
    QPushButton* m_popOutBtn{};
    QWidget*     m_floatingWindow{};   // nullptr when docked
    int          m_stackIndex{-1};     // slot in PanadapterStack

public slots:
    void popOut();
    void popIn();
};

---

No duplicate found in the open issues — this is a fresh feature request ready to paste into GitHub. The only tangentially related open work is **#152** (multi-panadapter), so you may want to cross-link the two issues since pop-out becomes especially useful once multiple pans are available.