The small dark window floating above everything is a panel (HUD style)
Panel (Floating Window / HUD)
/ NSPanel · NSWindow.StyleMask.nonactivatingPanel /
also called floating panel, utility panel, HUD window, heads-up display
A panel is an auxiliary window for tools, controls, or transient information rather than a primary document. It can float above normal windows, hide when its app becomes inactive, or use a HUD appearance. A non-activating panel can accept appropriate interaction without bringing the entire app forward, which suits command launchers and Spotlight-like surfaces.
If you called it…
…you meant a panel (floating window / hud).
Anatomy — every part, named
- 1Floating window level
NSWindow.Level.floating“The utility window that stays above the document” uses a floating window level.
- 2HUD chrome
NSWindow.StyleMask.hudWindow“The dark translucent heads-up-display frame” is HUD chrome.
Prompt — paste into your agent
Implement this auxiliary surface as a Panel (Floating Window / HUD) using NSPanel, with NSWindow.Level.floating so it stays above its related document windows. If it should behave like Spotlight, use the nonactivatingPanel style so showing it does not activate the app or steal focus unnecessarily.
Debug prompt — when it misbehaves
Paste this, then describe what you’re seeing — it hands your agent the classic failure modes to rule out first.
Debug my macOS panel (NSPanel). Rule out: the panel stealing focus from the main window because the nonactivatingPanel style mask is missing; text fields inside refusing input because the panel cannot become key; the panel vanishing on app deactivate via hidesOnDeactivate; a floating window level fighting other always-on-top windows. The symptom:
In code
The exact names this thing goes by in code — each row is one framework’s word for it. Use the row that matches your project (or paste it into your prompt).
| AppKit | NSPanel | |
| AppKit | NSWindow.StyleMask.nonactivatingPanel | allows a panel that does not activate its app |
| AppKit | NSWindow.StyleMask.hudWindow | heads-up-display panel appearance |
| AppKit | NSWindow.Level.floating | |
| AppKit | NSPanel.becomesKeyOnlyIfNeeded |