Show HN: SpinWin - A macOS menu bar app to visually rotate or spin any window

How It Works

A macOS menubar utility that visually rotates a selected window by any angle (90° increments, arbitrary angles, or a continuous spin).

macOS has no public API to rotate another app's window. Real rotation would require private SkyLight calls (CGSSetWindowTransform) with System Integrity Protection disabled - not worth it. Instead, SpinWin fakes it:

• Hide the selected window off-screen via the Accessibility API. It keeps rendering there, so it can still be captured.
• Capture its contents continuously with ScreenCaptureKit (SCStream + desktopIndependentWindow filter) - this grabs only that window's buffer, so the overlay never mirrors itself.
• Draw the frames in a transparent, borderless overlay window placed where the original was, rotated with a CALayer transform.

Because it's a layer transform, any angle works - the overlay is sized to the rotated content's bounding box so nothing clips, and a diagonal-sized square is used while spinning.

Installation & Building

The easiest way to get SpinWin is the latest release - the download is signed with a Developer ID and notarized by Apple, so it launches without Gatekeeper warnings.

Or build it yourself:

./scripts/build-app.sh # builds SpinWin.app (release)
open SpinWin.app       # grant Screen Recording + Accessibility

For quick iteration during development:

swift build && swift run SpinWin

Usage

Left-click the menubar icon to start: choose a rotation in the bottom options bar (a preset angle, a spin speed + direction, or free rotation), then click the window you want.

Drag the overlay to reposition it; drag its handle to rotate freely. Press Esc on the overlay to stop and restore the window.

Right-click (or Control-click) the icon for the menu: active rotations (with per-window angle/spin controls), Stop all, and Quit.

Required Permissions

• Screen Recording - to capture the window contents.
• Accessibility - to move the source window off-screen and restore it.

Caveats / Limitations

• The overlay is a live picture, not interactive. You can drag and rotate it, but clicks and keystrokes are not sent to the real window underneath.
• Mission Control / Exposé leak. The hidden window is parked off-screen but still a real window, so Exposé shows it unrotated. There is no public API to exclude another app's window from Mission Control, and minimizing it would stop the capture.
• Some apps throttle rendering of off-screen windows, which can slow the feed.
• A window that resizes itself while rotated keeps its original footprint. You can't drag-resize the hidden window, but an app can still resize it on its own (a video player adapting to a new track, a terminal responding to an escape sequence). The capture is letterboxed into the original size until you stop and rotate it again.

Files