G9 Helper

A lightweight macOS menu bar utility that unlocks crisp HiDPI (Retina) scaling on Samsung Odyssey G9 and other large monitors.

Free and open source - if you find it useful, consider buying me a coffee!

The Problem

macOS only enables HiDPI rendering on displays meeting certain pixel density thresholds. Large monitors like the Samsung Odyssey G9 (57" or 49") don't qualify, forcing you to choose between:

• Native resolution with text too small to read comfortably
• Scaled resolution with blurry, non-Retina rendering

The Solution

G9 Helper creates a virtual display with HiDPI enabled at your preferred resolution, then mirrors it to your monitor. macOS renders everything at 2x into the virtual framebuffer, giving you sharp, Retina-quality text on any display.

Supported Monitors

Monitor	Native Resolution	Recommended Setting
Samsung Odyssey G9 57"	7680x2160	5120x1440 HiDPI
Samsung Odyssey G9 49"	5120x1440	3840x1080 HiDPI
34" Ultrawide	3440x1440	2560x1080 HiDPI
4K Displays	3840x2160	2560x1440 HiDPI

Installation

Download

1. Download G9.Helper-v1.0.6.dmg from Releases
2. Open the DMG and drag G9 Helper to Applications
3. Launch from Applications or Spotlight
4. Look for the display icon in your menu bar

Build from Source

git clone https://github.com/knightynite/HiDPIVirtualDisplay.git
cd HiDPIVirtualDisplay/App
./build.sh
cp -r "build/G9 Helper.app" /Applications/

First Launch

macOS may block the app on first run. Right-click the app, select "Open", then click "Open" in the dialog.

Usage

1. Click the display icon in your menu bar
2. Select your monitor type from the submenu
3. Choose a resolution preset
4. Wait a few seconds for the configuration to apply

To disable, click the menu bar icon and select Disable HiDPI.

Resolution Presets

Samsung G9 57" (7680x2160)

Preset	Effective Resolution	Notes
Native 2x	3840x1080	Largest UI, sharpest text
5120x1440	5120x1440	Best balance (recommended)
4800x1350	4800x1350	Slightly larger UI
4480x1260	4480x1260	Larger UI elements

Samsung G9 49" (5120x1440)

Preset	Effective Resolution
3840x1080	3840x1080 (recommended)
Native 2x	2560x720

Auto-Start & Crash Recovery

The app includes built-in crash recovery. If enabled, your HiDPI settings will automatically restore after a crash or system restart.

Enable Auto-Start (Recommended)

cd /path/to/HiDPIVirtualDisplay/App
./install-launchd.sh install

This will:

• Start G9 Helper automatically at login
• Auto-restart if the app crashes
• Automatically restore your last HiDPI preset

Disable Auto-Start

./install-launchd.sh uninstall

Check Status

./install-launchd.sh status

Requirements

• macOS 12.0 Monterey or later
• Apple Silicon recommended (M1/M2/M3/M4)
  • Base chips support up to 6144px horizontal
  • Pro/Max/Ultra support 7680px+ horizontal
• Intel Macs may work with limitations

Known Issues

Periodic Crashes

The app uses private macOS APIs for virtual display creation. These APIs have internal memory management that can occasionally cause crashes. The app is designed to handle this gracefully:

1. Auto-restart: With the launch agent installed, crashes restart automatically within seconds
2. State preservation: Your preset is saved and restored on restart
3. Transparent recovery: Most users won't notice the brief restart

This is a known limitation of using private APIs. The display configuration persists through crashes.

Limitations

• Refresh rate depends on resolution and hardware configuration
• HDR may not function in mirrored mode
• May require re-enabling after sleep/wake cycles
• Uses private macOS APIs (may break with future updates)

Uninstall

1. Remove auto-start (if enabled):

   ./install-launchd.sh uninstall

2. Click the G9 Helper menu bar icon and select Quit
3. Drag G9 Helper.app from Applications to Trash
4. Empty Trash

Project Structure

HiDPIVirtualDisplay/
├── App/                          # Menu bar GUI application
│   ├── Sources/                  # Swift & Objective-C source
│   │   ├── HiDPIDisplayApp.swift # Main app with SwiftUI
│   │   ├── VirtualDisplayManager.m # Display management (no-ARC)
│   │   └── CGVirtualDisplayPrivate.h # Private API declarations
│   ├── Resources/                # App icon
│   ├── launch-agent/             # launchd auto-start plist
│   ├── build.sh                  # Build script
│   ├── install-launchd.sh        # Auto-start installer
│   └── Info.plist                # App bundle config
├── Sources/                      # Command-line tool (alternative)
│   ├── main.swift                # CLI entry point
│   └── VirtualDisplayManager.*   # Shared display management
├── Makefile                      # CLI build system
└── README.md

Troubleshooting

App won't open: Right-click and select "Open", then confirm in the security dialog.

Resolution doesn't apply: Disable HiDPI first, wait a few seconds, then try again.

Display issues after changing monitor settings: Quit and relaunch the app.

Virtual display persists after quit: Restart your Mac to clear orphaned displays.

Frequent crashes: Install the launch agent for automatic recovery:

./install-launchd.sh install

How It Works

The app leverages macOS private APIs to create virtual displays with custom properties:

1. Creates a virtual display with HiDPI flag and 2x framebuffer
2. Configures display mirroring from virtual to physical display
3. macOS renders at 2x resolution into the virtual framebuffer
4. The framebuffer is scaled to your monitor's native resolution

Technical Notes

• Built with Swift (UI) and Objective-C (display management)
• VirtualDisplayManager compiled without ARC (-fno-objc-arc) for manual memory control
• Window tracking to prevent framework-related crashes
• UserDefaults for state persistence across crashes

Support

If G9 Helper improves your workflow, consider supporting development:

License

MIT License - Free software, use at your own risk.

This software uses undocumented macOS APIs that may change or break with future updates.

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Created with ❤️ by AL in Dallas