StayAwake

StayAwake is a performance-focused, lightweight Windows utility designed to manage system power states with surgical precision. While tools like "DontSleep" offer a wide array of complex features, StayAwake is built for users seeking an absolute minimalist approach—prioritizing a tiny memory footprint of ~1.4 MB and direct system interaction.

---

🛠 How it Works

StayAwake operates by interacting directly with the Windows Power Manager via the SetThreadExecutionState API. It prevents the system from entering sleep or turning off the display by flagging the current thread as required for system or display activity.

Operating Modes

The application features two distinct modes, toggled by a left-click on the tray icon:

Mode	Visual Indicator	Functionality
StayAwake	Red Screen	Keeps the system and monitor active indefinitely (ES_DISPLAY_REQUIRED).
Auto-Off	Dark Screen	Allows the monitor to turn off after a specific idle period.

In Auto-Off mode, the application monitors user activity via GetLastInputInfo. Once the idle time exceeds the configured limit, it broadcasts a SC_MONITORPOWER command to power down the displays.

⚡ Quick Actions

StayAwake supports rapid interaction through modifier keys:

Action	Interaction	Functionality
Instant Off	Shift + Left-Click	Immediately powers down all monitors without changing the current operating mode.

---

📊 Visual Feedback (Tray Icon)

The tray icon is rendered dynamically using the Windows Graphics Device Interface (GDI) to avoid external dependencies.

• Dynamic Progress: In Auto-Off mode, a Blue Bar fills the monitor icon as the idle time approaches the limit.
• Status Colors: The screen remains Red when forced awake and turns Dark when the timer is active.
• High-DPI Support: StayAwake is "Per-Monitor DPI Aware V2". The icon is immediately redrawn without blurriness during scaling changes or monitor swaps (WM_DPICHANGED).

---

🛠 Technical Highlights

• Hybrid Event Loop: Uses MsgWaitForMultipleObjects to simultaneously listen for Windows messages and file system events. This ensures immediate reaction to configuration changes with zero CPU usage while waiting.
• Atomic Configuration: Settings are saved using a temporary-file-swap pattern to prevent data corruption during system crashes.
• Resource Management: In "StayAwake" mode, the internal heart-beat timer is fully deallocated (KillTimer) to eliminate unnecessary CPU cycles.
• Instant Reload: Utilizing FindFirstChangeNotificationW, StayAwake monitors its configuration directory and applies changes to the .conf file in real-time without a restart.

---

⚙️ Configuration

Settings are stored in a plain-text file:

%LOCALAPPDATA%\StayAwake\stay_awake.conf

File Format: Two space-separated integers:

1. Mode: 0 (StayAwake) or 1 (Auto-Off).
2. Timeout: Idle limit in seconds (default: 300).

---

🚀 Deployment & Instance Management

📦 Installation via mise

StayAwake is optimized for use with mise:

# Installation via mise
mise use -g github:TheFranconianCoder/stay-awake

🔄 Seamless Updates (Force Takeover)

StayAwake includes a Single Instance Mutex and a dedicated takeover logic:

1. It detects an existing instance via the SA_CLASS window class.
2. It sends a WM_CLOSE signal to the old instance to trigger a clean exit (removing the tray icon).
3. After a brief delay (RESTART_DELAY_MS), the new version takes over the tray position.

🔑 Automated Autostart

The application manages its own persistence. Upon every launch, it updates the HKCU\...\Windows\CurrentVersion\Run registry key to ensure the autostart always points to the current binary path—essential for path changes after a mise upgrade.

---

🏗 Build Instructions

The project is built using the Zig toolchain.

zig build

The build.zig is configured to generate stripped, LTO-optimized binaries to maintain a minimal footprint.