Gaffer

A macOS menubar app that applies black corner masks to wallpapers, matching the rounded window corners in macOS Tahoe.

What it does

macOS Tahoe introduced rounded window corners, but the desktop wallpaper still has sharp corners. Gaffer processes your wallpaper to add black fills in the corners, creating a seamless look where the wallpaper appears to have the same rounded corners as your windows.

Features

• Corner size options: None, Small, Medium, Large (matching different window styles)
• Dynamic wallpaper support: Works with multi-frame HEIC wallpapers (like Solar Gradients)
• Appearance modes: Dark, Light, or Auto (follows system appearance)
• Multi-display support: Handles each display independently with correct aspect ratios
• Multi-space support: Apply to all virtual desktops with one click
• Event-driven updates: Responds instantly to space/display changes without constant polling
• Power-aware: Adjusts burst mode frequency based on AC/battery status
• Start on login: Optional login item support

Installation

Homebrew

brew install jaamesd/tap/gaffer

Manual

1. Download Gaffer.zip from Releases
2. Extract and move Gaffer.app to /Applications
3. Right-click and select "Open" (required for first launch)
4. Click "Open" in the dialog

After the first launch, you can open normally.

Building from source

./build-app.sh

This creates Gaffer.app in the project directory.

Requirements

• macOS 13.0 (Ventura) or later
• Apple Silicon or Intel Mac

How it works

Gaffer monitors your wallpaper and processes it to add black corners. The processed wallpapers are cached in ~/Library/Application Support/Gaffer/ for fast switching between spaces.

License

MIT