Win-Float

win-float is a lightweight workspace utility for Windows written in Rust. It allows you to toggle "Always-On-Top" states and adjust transparency for any window using global hotkeys. The app draws click-through overlays using 2D vector graphics (tiny-skia) for real-time visual HUD feedback.

This is mostly a learning project to explore Windows APIs and Rust desktop utility development.

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Features

1. Always-On-Top Toggle (Ctrl + Win + F11)

• Toggles the topmost state of the active foreground window.
• Draws a transparent, click-through pin overlay in the top-right corner of the target window.
• Focused Accent Outline: When a pinned always-on-top window is focused, an outline matching the Windows system accent color is drawn around it to indicate its focus state. The outline automatically disappears when it loses focus.

2. Transparency Adjustment Modal (Shift + Win + F11)

• Enters a dedicated block-input state targeting the active foreground window.
• Keyboard Navigation:
  • Left / Down / -: Decrease opacity (more transparent).
  • Right / Up / +: Increase opacity (more opaque).
  • Any other key: Commits the current transparency setting, exits the modal, and restores normal keyboard input.
• Physics-Based Slider HUD: Displays a floating HUD overlay near the window showing the current opacity percentage with a smooth, physics-animated slider bar.
• Seeding from Current State: Re-entering the modal automatically queries the window's existing opacity and seeds the slider, avoiding visual jumps.

3. Shell & System Window Exclusion

• Safety Block: Automatically rejects operations on system components like the Taskbar, system tray notification area, tray clock, overflow tray popup (^), Quick Settings panel, Action Center flyouts, volume indicators, desktop backgrounds, and third-party Start menus.
• Hierarchical Scanning: Climbs window owner and ancestor chains (including popups, nested browser canvas elements, and owned popups) to ensure focus outline status is correctly inherited and sub-components are not targeted.
• Operational Logging: Prints clear console warnings detailing the Class, Process name, and HWND of the rejected system window.

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Tech Stack & Windows APIs

• Core Language: Rust (Edition 2024)
• Graphics Rendering: tiny-skia for zero-allocation 2D vector drawings.
• Platform APIs (windows crate):
  • GetForegroundWindow / SetWindowPos (Topmost state).
  • GetWindowLongW / SetWindowLongW / SetLayeredWindowAttributes (Window layering and alpha opacity).
  • SetWindowsHookExW (WH_KEYBOARD_LL low-level keyboard hook) for capturing layout adjustments without swallowing system-wide keys.
  • SetWinEventHook (EVENT_OBJECT_LOCATIONCHANGE, EVENT_OBJECT_DESTROY, EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_MOVESIZESTART, EVENT_SYSTEM_MOVESIZEEND) for location tracking, focus change handler triggers, and state cleanup.
  • DwmGetColorizationColor (Accent color query).
  • SetConsoleCtrlHandler + PostThreadMessageW (Graceful daemon shutdown routing).
  • GetAncestor / GetWindow (Window owner and ancestor tree climbing).
  • OpenProcess / QueryFullProcessImageNameW (Process executable name query for system window exclusion).
  • IsZoomed (Check if the target window is maximized).
  • SetTimer / KillTimer (Win32 window message timers for snapping animations debouncing).

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Architecture

Following Test-Driven Development (TDD) principles, all platform-dependent layers are fully decoupled behind abstract Rust traits. This enables comprehensive mocking and testing of the application controller without making real Win32 OS calls.

win-float/
├── Cargo.toml
└── src/
    ├── traits.rs           # Decoupling traits (WindowManager, InputHook, etc.) and Mocks
    ├── transparency_calc.rs # Pure mathematical functions for opacity-to-alpha mapping
    ├── hud_layout.rs       # Coordinate/boundary layout math for pins & HUD boxes
    ├── state_machine.rs    # Core transition state machine (Idle <-> Modal)
    ├── app/
    │   ├── mod.rs
    │   ├── controller.rs   # Application event controller & physics loop
    │   └── tracker.rs      # WinEvent hook tracker implementation
    ├── platform/
    │   ├── mod.rs
    │   ├── hook.rs         # Live keyboard capture hook wrapper
    │   └── window.rs       # Live window/overlay management implementation
    ├── ui/
    │   ├── mod.rs
    │   ├── draw.rs         # 2D HUD widget and pin renderer
    │   └── overlay.rs      # Overlay canvas pixels buffer wrapper
    └── main.rs             # Daemon entry point and lifecycle watchdog

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Setup & Installation

Requirements

• Windows 10 or Windows 11.
• Rust toolchain (Edition 2024).

Build & Run

To compile the release binary:

cargo build --release

To run the utility:

cargo run --release

Running Tests

To run the full decoupled test suite (47 unit & integration tests):

cargo test

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Reliability & Safety Design

• Safety Hook Proc: The low-level keyboard hook proc resolves keyboard captures using CallNextHookEx to ensure key event chains are never dropped system-wide.
• Crash-Resilient Watchdog: To ensure user windows are not left permanently transparent or locked if the app crashes, the binary launches a background watchdog process. In the event of a main process crash, the watchdog intercepts the state, recovers the target windows, and restores their original styling.
• State Reset on Termination: Pinned always-on-top states and transparency adjustments are automatically reverted back to their original styles and layers when the application is terminated, closed, or exited (either gracefully or recovered via the watchdog).
• Graceful Exit: Responds to Ctrl+C or Console Exit events by safely routing thread notifications, tearing down hook handlers, and cleaning up window style modifications immediately.

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License

This project is licensed under the MIT License.