DisplayCut

A macOS menu bar application for controlling display blackout on multiple monitors. DisplayCut allows you to selectively black out individual displays, with support for automatic built-in display blackout when external displays are connected.

Features

• Multi-Display Support: Manage blackout state for each connected display independently
• Two Blackout Modes:
  • Window Mode: Uses fullscreen black window overlays (works on all displays)
  • Software Dimming Mode: Uses gamma adjustment and DDC brightness control (for supported displays)
• Auto-Blackout: Automatically black out the built-in display when external displays are connected
• Mouse Guard: Prevents mouse cursor from entering blacked-out displays
• Persistent Settings: Remembers blackout states across app restarts and display reconnections
• Display Detection: Automatically detects when displays are connected or disconnected

Requirements

• macOS 13.0 (Ventura) or later
• Xcode 15.0 or later (for building from source)

Installation

Building from Source

1. Clone the repository:

git clone https://github.com/yourusername/DisplayCut.git
cd DisplayCut

2. Open the project in Xcode:

open DisplayCut.xcodeproj

3. Build and run the project (⌘R)

4. The app will appear in your menu bar with a display icon

Usage

Basic Usage

1. Click the display icon in your menu bar
2. Select a display from the list
3. Click on the display to toggle its blackout state

Blackout Modes

Choose between two blackout modes in the menu:

• Window Mode: Creates a fullscreen black window overlay. This is the default mode and works reliably on all displays.
• Software Dimming Mode: Uses gamma adjustment and DDC brightness control. Provides deeper control but requires DDC support for external displays.

Auto-Blackout

Enable "Auto-Blackout" to automatically black out the built-in display when external displays are connected. The built-in display will be restored when all external displays are disconnected.

Display Management

• Each display shows its current state (enabled or blacked out)
• Built-in displays are marked with a laptop icon
• External displays are marked with a display icon
• Blacked-out displays show an orange status indicator

Architecture

The application is built using SwiftUI and follows a modular architecture:

• Core: Display management, settings persistence, and display observation
• Blackout: Blackout provider implementations (Window and Software Dimming)
• Utilities: DDC control, gamma control, and mouse guard functionality
• Views: Menu bar interface

Key Components

• DisplayManager: Central manager for display enumeration and blackout state
• BlackoutProvider: Protocol for blackout implementations
• WindowBlackoutProvider: Window-based blackout implementation
• SoftwareBlackoutProvider: Gamma/DDC-based blackout implementation
• MouseGuard: Prevents mouse cursor from entering blacked-out displays
• SettingsManager: Handles persistent settings storage

Technical Details

Display Identification

Displays are identified using a stable identifier based on vendor ID, model ID, and serial number. This ensures that blackout states persist across reboots and display reconnections, even if the CoreGraphics display ID changes.

DDC Control

For external displays that support DDC/CI, the software dimming mode can control brightness directly. This provides a more hardware-level blackout compared to window overlays.

Gamma Control

The software dimming mode uses CoreGraphics gamma tables to darken displays. Original gamma values are saved and restored when displays are un-blackouted.

License

[Add your license here]

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Acknowledgments

• Built with SwiftUI and AppKit
• Uses CoreGraphics for display management
• DDC control implementation for external display brightness