GPX Battery

A tiny, portable Windows tray app that shows the battery percentage of Logitech wireless mice (built for the G Pro X Superlight 2, works with any HID++ 2.0 Logitech mouse). No G HUB required, no runtime dependencies — a single exe.

Made with performance in mind using Rust, the thread runs only when you want it to.

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How it works

1. Discovery — the app enumerates HID interfaces with Logitech's vendor id (0x046D) and the vendor-specific HID++ usage pages (0xFF00/0xFF43). Lightspeed/Unifying receivers are probed on all six pairing slots; mice connected over Bluetooth or USB cable answer directly. Mice that go offline (switched off) stay listed as "off" and reappear the moment they come back.
2. Battery — each mouse is queried over the HID++ 2.0 protocol: feature 0x1004 Unified Battery (Superlight 2), with fallbacks to 0x1000 Battery Status and 0x1001 Battery Voltage for older devices.
3. Polling — a background thread performs that few-millisecond exchange at the configured interval (default: every 60 s) and sleeps in between, so idle CPU usage is zero and there is no impact while gaming. Device plug/unplug triggers an immediate re-scan via WM_DEVICECHANGE.
4. Tray — one icon per selected mouse, drawn at runtime with GDI. White number normally, amber below 30 %, red below 15 %, green when charging, gray ? when the mouse is off.

Usage

Run gpx-battery.exe. A welcome window confirms the app is running and shows the first detected mouse; the app then lives in the system tray.

• Tray icon menu (left or right click)
  • Devices — every detected wireless Logitech mouse with its current percentage; check/uncheck to show or hide its tray icon
  • Refresh now — re-scan and re-read immediately
  • Settings… — options window
  • Exit
• Settings window (dark, G HUB-style)
  • Poll interval: any value in seconds / minutes / hours
  • Start with Windows (HKCU Run registry entry)
  • Show welcome window at startup
  • Icon style: percentage number or battery bar
  • Low-battery notification with adjustable threshold
  • Changes take effect when you click Apply

Settings storage

The app runs on built-in defaults and creates no files until you click Apply, at which point settings.json is written to %APPDATA%\gpx-battery (shown at the top of the settings window). The red Delete app data button removes every file the app has created, disables autostart and resets all settings to defaults. - Full cleanup.

Building

cargo build --release

The exe icon, version info and DPI-awareness manifest are embedded by build.rs; everything is statically linked.