Desktop Labeler (mddsklbl)

A lightweight Windows overlay that shows a per–virtual-desktop title at the top center of your primary monitor. It is always-on-top, transparent, and pinned across desktops. Use global hotkeys or the tray menu to update the title/description for the current virtual desktop. Text is persisted per desktop and restored on restart.

Features

• Per-desktop labels (Title and optional Description), persisted in JSON.
• Event-driven virtual desktop switch detection (Windows 11 24H2+), with seamless polling fallback.
• Transparent, crisp text rendering (DirectWrite/Direct2D) with a subtle backdrop; GDI fallback.
• Global hotkeys (configurable) and a small system tray menu.
• DPI-aware placement (Per-Monitor v2) and primary work-area centering.
• Accessibility- and focus-friendly behavior: auto-hide in High Contrast or when an app is fullscreen.

Requirements

• Windows 11. Event notifications need Windows 11 24H2+; earlier builds fall back to a light poller.
• Rust toolchain (if building): stable Rust, cargo, MSVC target.

Build & Run (from source)

# In this repository
cargo build --release
# Run (dev)
cargo run

The first launch creates a default configuration file under your roaming profile.

Tray Menu & Hotkeys

• Tray menu: Edit Title, Edit Description, Toggle Overlay, Open Config, Exit.
• Default hotkeys (changeable in config):
  • Ctrl+Alt+T — Edit Title
  • Ctrl+Alt+D — Edit Description
  • Ctrl+Alt+O — Toggle overlay visibility
  • Ctrl+Alt+L — Snap overlay position (cycle 1/4, 1/2, 3/4) If any hotkey cannot be registered (OS conflict), it is skipped; adjust in the config.

Configuration

Configuration is stored per-user at:

%APPDATA%\Acme\DesktopLabeler\config\labels.json

The app writes atomically (temp file + replace). A minimal schema:

{
  "desktops": {
    "{GUID}": { "title": "Work", "description": "Focus on tickets" },
    "{GUID}": { "title": "Meetings", "description": "Teams/Zoom" }
  },
  "hotkeys": {
    "edit_title":       { "ctrl": true, "alt": true, "shift": false, "key": "T" },
    "edit_description": { "ctrl": true, "alt": true, "shift": false, "key": "D" },
    "toggle_overlay":   { "ctrl": true, "alt": true, "shift": false, "key": "O" },
    "snap_position":    { "ctrl": true, "alt": true, "shift": false, "key": "L" }
  },
  "appearance": {
    "font_family": "Segoe UI",
    "font_size_dip": 16,
    "margin_px": 8,
    "hide_on_fullscreen": false
  }
}

Notes

• Desktop keys are the OS GUIDs for each virtual desktop. The app discovers the current GUID automatically; you don’t need to prefill them.
• The edit dialogs enforce a simple input cap (200 chars) to keep the overlay tidy.

Visibility & Accessibility

The overlay’s visibility is governed by:

• Your toggle state (hotkey or tray → Toggle Overlay)
• High Contrast mode: overlay auto-hides when OS High Contrast is ON; restores when OFF
• Fullscreen detection: hides if a foreground window fully covers the primary monitor Together: the overlay shows only when Toggle=ON AND not High Contrast AND not Fullscreen.

Virtual Desktop Detection

• Preferred: winvd event listener on Windows 11 24H2+ for instant switches.
• Fallback: a 250ms poller (low CPU) if events are unavailable.
• The overlay window is pinned to all desktops so it remains present; only the text changes with the current GUID.

Rendering & Placement

• DirectWrite + Direct2D draw the label with per-pixel alpha onto a 32-bit top-down DIB, then UpdateLayeredWindow presents it.
• A subtle translucent backdrop improves legibility over busy wallpapers.
• Placement uses the primary monitor’s work area (excludes taskbar): centered horizontally, offset by appearance.margin_px from the top.

Logging

Logs are written to %LOCALAPPDATA%\Acme\DesktopLabeler\logs\mddsklbl.YYYY-MM-DD.log. Control verbosity with RUST_LOG (e.g., RUST_LOG=info or RUST_LOG=debug).

Troubleshooting

• Overlay not visible
  • High Contrast may be active — disable it, or rely on tray Toggle.
  • A fullscreen app may be in the foreground — Alt+Tab out or exit fullscreen.
  • You may have toggled it off — use Ctrl+Alt+O or the tray menu.
• Hotkey didn’t work
  • Some combinations are reserved by Windows; pick alternatives in labels.json.
• Titles don’t follow desktop switches
  • On older Windows 11 builds (pre-24H2), the app uses polling. It should still update within ~250ms.
• Multiple instances
  • The app runs as a single instance by class detection; if an instance is already running, a new one will exit.

Development

• Format & lint: cargo fmt --all and cargo clippy -- -D warnings
• Tests: cargo test
• Run (verbose logs): set RUST_LOG and run with cargo run

Project layout

src/
  config.rs   # JSON schema + atomic save/load
  hotkeys.rs  # Register/Unregister helpers and IDs
  vd.rs       # Virtual desktop GUID + event/poller
  tray.rs     # Shell_NotifyIconW tray and menu
  overlay.rs  # Layered-window renderer (DWrite/D2D with fallback)
  ui.rs       # Minimal input dialog (Edit Title/Description)
  lib.rs      # Module exports
  main.rs     # Win32 window, message loop, wiring

Security & Privacy

• No elevated privileges required; writes only under your %APPDATA%/Acme/DesktopLabeler directory.
• No network access or telemetry.

Roadmap

• Config hot-reload via file watcher, refined logging, packaged installer (Inno/WiX), and optional Run‑at‑Login toggle.

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If anything is unclear or you want this tailored for your deployment (MSI packaging, group policy defaults, etc.), open an issue or ask for a customized build profile.