MonitorConfig - Rust CLI

A native Windows CLI tool for managing monitor settings via DDC/CI, written in Rust. This is a complete rewrite of the original PowerShell module.

Features

• List Monitors: Enumerate all connected monitors
• Brightness Control: Get and set monitor brightness levels
• Contrast Control: Get and set monitor contrast levels
• VCP Support: Full VCP (VESA Command Protocol) feature access
• Monitor Capabilities: Query monitor capabilities string
• Settings Management: Save current settings or reset to factory defaults
• JSON Output: All commands support JSON output for scripting
• Resume-safe Execution: Built-in --wait and --retry flags for reliable post-sleep/hibernate automation

Requirements

• Windows 10/11 (uses dxva2.dll and user32.dll)
• Rust 1.93.0+ (Edition 2024)
• External monitors must support DDC/CI (enable in monitor OSD if needed)

Building

Prerequisites

Install Rust from rustup.rs:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Build Release Version

cargo build --release

The compiled binary will be at target/release/monitorconfig.exe

Install Globally

cargo install --path .

Usage

List All Monitors

monitorconfig list

# JSON output
monitorconfig list --json

Get Brightness

# Primary monitor
monitorconfig get-brightness --primary

# Specific monitor
monitorconfig get-brightness --device "\\.\DISPLAY1"

# JSON output
monitorconfig get-brightness --primary --json

Set Brightness

# Set primary monitor to 50%
monitorconfig set-brightness 50 --primary

# Set specific monitor
monitorconfig set-brightness 75 --device "\\.\DISPLAY1"

Get Contrast

monitorconfig get-contrast --primary

Set Contrast

monitorconfig set-contrast 60 --primary

Get VCP Feature

# Get brightness (VCP code 0x10)
monitorconfig get-vcp 0x10 --primary

# Get power mode (VCP code 0xD6)
monitorconfig get-vcp 0xD6 --primary --json

Set VCP Feature

# Set brightness via VCP
monitorconfig set-vcp 0x10 75 --primary

# Turn off monitor (power mode = 4)
monitorconfig set-vcp 0xD6 4 --primary

# Set color temperature preset, with startup wait and retries (safe for Task Scheduler / post-resume)
monitorconfig set-vcp 0x14 11 --device "Lenovo L22i-40" --wait 10 --retry 3 --retry-delay 8 --silent

set-vcp Options

Option	Short	Default	Description
--device <NAME>	-d	—	Target monitor by device path or friendly name
--primary	-p	—	Target the primary monitor
--wait <SECONDS>	-w	0	Sleep this many seconds before acquiring any monitor handle. Useful after resume from sleep/hibernate to give the monitor's DDC/CI firmware time to fully initialize before the first I²C command is sent.
--retry <COUNT>	—	0	Retry the command up to COUNT additional times if it fails
--retry-delay <SECONDS>	—	5	Seconds to wait between retry attempts
--silent	-s	—	Suppress all console output

Why --wait instead of a Task Scheduler trigger delay? The Task Scheduler <Delay> counts from when the event fires (e.g. resume detected), not from when the display driver finishes restoring the monitor signal. The monitor's internal DDC/CI controller can take an additional 10–15 seconds after the display comes back before it accepts I²C commands. --wait delays inside the process, after the display driver is already up, giving a more reliable buffer. Sending a DDC/CI command to a monitor whose firmware MCU is still initializing can cause the monitor to hang and require a power cycle to recover.

List Known VCP Codes

# Show reference list of common VCP codes
monitorconfig list-vcp

# JSON output
monitorconfig list-vcp --json

Scan Monitor for All Supported VCP Codes

# Scan primary monitor for all supported VCP codes
monitorconfig scan-vcp --primary

# Scan specific monitor
monitorconfig scan-vcp --device "\\.\DISPLAY1"

# JSON output for scripting
monitorconfig scan-vcp --primary --json

Note: list-vcp shows a static reference list of common VCP codes, while scan-vcp actively queries your monitor to discover which codes it actually supports (similar to PowerShell's Get-MonitorVCPResponse -All).

Get Monitor Capabilities

monitorconfig get-capabilities --primary

Save Settings

# Save current settings to monitor's memory
monitorconfig save-settings --primary

Reset to Factory Defaults

# Reset all settings
monitorconfig reset-defaults --primary

# Reset only color settings
monitorconfig reset-defaults --primary --color-only

Global Flags

These flags work with every command:

Flag	Short	Description
--silent	-s	Suppress all console output
--wait <SECONDS>	-w	Sleep before executing (see above)

Background Tasks / Task Scheduler

When running MonitorConfig from Windows Task Scheduler or other background automation tools, use --silent to suppress console output and the --wait / --retry flags to handle timing issues around resume from sleep or hibernate.

Silent Mode

Use the global --silent (or -s) flag to suppress all console output:

monitorconfig set-vcp -d "Lenovo L22i-40" 0x14 11 --silent
monitorconfig set-brightness 50 --primary -s

Resume-safe Task Scheduler Pattern

Monitors can take 10–15 seconds after a sleep/hibernate resume before their DDC/CI controller is ready to accept commands. Sending a command too early may cause the monitor to hang (black screen requiring a power-cycle to recover).

Use --wait to delay inside the process and --retry to automatically re-attempt if the monitor is still not ready:

monitorconfig set-vcp -d "Lenovo L22i-40" 0x14 11 -s --wait 10 --retry 3 --retry-delay 8

Recommended Task Scheduler settings for resume triggers:

Setting	Recommended Value	Reason
Trigger <Delay>	PT2S	Just enough for the process to be schedulable; real delay is handled by --wait
<ExecutionTimeLimit>	PT2M	Accommodates --wait 10 + up to 3 retries × 8 s = ~50 s worst case
<MultipleInstancesPolicy>	IgnoreNew	Prevents duplicate runs if multiple resume events fire simultaneously

Complete Console Window Suppression

For Windows builds, you can compile the binary to completely hide the console window using Cargo features. This prevents even the brief flash when running from Task Scheduler.

Build with GUI subsystem (no console window):

cargo build --release --features gui-subsystem

For cross-compilation from Linux:

cargo build --release --target x86_64-pc-windows-gnu --features gui-subsystem

Note: GUI subsystem builds produce no console output at all, including errors. Only use this for production automation where errors are logged elsewhere. For development and testing, use the standard build without the feature flag.

Common VCP Codes

Code	Name	Description
0x10	Brightness	Luminance of the image
0x12	Contrast	Contrast of the image
0x14	Color Temperature	Select color temperature
0x16	Red Video Gain	Red video gain (drive)
0x18	Green Video Gain	Green video gain (drive)
0x1A	Blue Video Gain	Blue video gain (drive)
0x60	Input Source	Select input source
0x62	Audio Speaker Volume	Audio speaker volume
0x8D	Audio Mute	Audio mute/unmute
0xD6	Power Mode	DPM/DPMS status (1=On, 4=Off)

Examples

Set Multiple Monitors to Same Brightness

# List monitors and get device names
monitorconfig list

# Set each monitor
monitorconfig set-brightness 80 --device "\\.\DISPLAY1"
monitorconfig set-brightness 80 --device "\\.\DISPLAY2"

Turn Off All Monitors

# Using VCP power mode command (value 4 = Off)
monitorconfig set-vcp 0xD6 4 --device "\\.\DISPLAY1"
monitorconfig set-vcp 0xD6 4 --device "\\.\DISPLAY2"

Query Monitor Information

# Get all info in JSON format
monitorconfig list --json > monitors.json
monitorconfig get-brightness --primary --json >> monitors.json
monitorconfig get-capabilities --primary >> capabilities.txt

Re-apply Color Preset After Resume (BrightStay pattern)

Some monitors (e.g. Lenovo L22i-40) reset certain VCP settings after waking from sleep. Use --wait and --retry to reliably re-apply the setting once the monitor's DDC/CI firmware is ready:

monitorconfig set-vcp -d "Lenovo L22i-40" 0x14 11 -s --wait 10 --retry 3 --retry-delay 8

Add this as a Task Scheduler action triggered by the resume/logon events (Microsoft-Windows-Power-Troubleshooter Event ID 1, Microsoft-Windows-Kernel-Power Event ID 507, Microsoft-Windows-Winlogon Event ID 7001).

Technical Details

Architecture

The tool is structured into several modules:

• native: Low-level Windows API bindings (dxva2.dll, user32.dll)
• monitor: Monitor abstraction and enumeration
• vcp: VCP (Video Control Panel) feature implementation
• cli: Command-line interface using clap
• error: Centralized error handling

DDC/CI Support

DDC/CI (Display Data Channel Command Interface) allows software control of monitor settings over the I²C bus embedded in the monitor cable. Most modern external monitors support it, but it may need to be enabled in the monitor's OSD (On-Screen Display) menu.

DDC/CI and Resume Timing

After a system resumes from sleep or hibernate, the display driver may report the monitor as available before the monitor's internal MCU has finished its own power-on initialization. The DDC/CI I²C bus operates at ~100 kHz and the monitor firmware needs to be fully ready before it can correctly handle incoming commands. Issuing a SetVCPFeature command during this window can corrupt the monitor's MCU state, causing a black screen that requires a full power cycle to recover.

The --wait flag addresses this by delaying command execution inside the process (after the OS-level display driver is already up), and --retry ensures that a transient failure during the initialization window does not cause the task to give up entirely.

Troubleshooting DDC/CI

1. Check if DDC/CI is enabled in monitor OSD
2. Try different cable types (DisplayPort usually works better than HDMI)
3. Update monitor firmware if available
4. Some USB-C docks may not support DDC/CI
5. If commands work manually but fail after resume, increase --wait in 5-second increments until reliable

Performance

The Rust implementation provides several advantages over the PowerShell module:

• Faster startup: No .NET CLR initialization overhead
• Lower memory usage: Compiled binary vs interpreted PowerShell
• Native performance: Direct Windows API calls without managed wrappers
• Smaller distribution: Single ~1MB executable (release build)

Migration from PowerShell Module

Command Mapping

PowerShell Cmdlet	Rust CLI Command
Get-Monitor	monitorconfig list
Get-MonitorBrightness	monitorconfig get-brightness
Set-MonitorBrightness	monitorconfig set-brightness
Get-MonitorVCPResponse	monitorconfig get-vcp
Set-MonitorVCPValue	monitorconfig set-vcp
Get-MonitorDetails	monitorconfig list --json
Save-MonitorSettings	monitorconfig save-settings
Reset-MonitorSettings	monitorconfig reset-defaults

Parameter Mapping

PowerShell Parameter	Rust CLI Option
-DeviceName	--device
-Primary	--primary
-VCPCode	First positional
-Value	Second positional

License

This project follows the same license as the original MonitorConfig PowerShell module (see LICENSE file).

Contributing

Contributions are welcome! Areas for improvement:

• Add WMI support for laptop internal displays
• Add configuration file support
• Add monitor profile save/restore
• Cross-platform support exploration (Linux/macOS DDC support)

Acknowledgments

Based on the MonitorConfig PowerShell Module by Martin Gräßlin.