Shaderlay - Android Overlay App

A system-wide shader overlay application for Android that applies RetroArch slang shaders on top of all content displayed on the screen.

Features

• System-wide overlay: Works over games, apps, and system UI using TYPE_APPLICATION_OVERLAY
• RetroArch slang shader compatibility: Supports parsing and rendering of slang shader format
• Real-time shader processing: Hardware-accelerated OpenGL ES rendering
• Performance optimization: Shader compilation caching and configurable performance modes
• Transparency control: Adjustable opacity for overlay effects
• Battery efficient: Power-aware rendering with frame rate limiting

Architecture

Core Components

1. OverlayService: Manages the system overlay window using WindowManager
2. GLOverlaySurfaceView: Transparent OpenGL surface for shader rendering
3. ShaderRenderer: OpenGL ES 2.0 renderer with shader pipeline
4. ShaderManager: Handles shader compilation and caching
5. Native Compiler: C++ shader compilation using simplified glslang approach
6. SlangParser: Parses RetroArch .slangp preset files

Shader Pipeline

Slang Shader → Native Compiler → GLSL → OpenGL Program → GPU Rendering

Performance Features

• Shader Caching: Compiled shaders cached to disk and memory
• Dynamic Quality: Performance-aware quality adjustments
• Frame Rate Control: Configurable FPS limits (30/60/120/unlimited)
• GPU Profiling: Real-time performance monitoring

Permissions

• SYSTEM_ALERT_WINDOW: Required for overlay functionality
• FOREGROUND_SERVICE: For persistent overlay service
• POST_NOTIFICATIONS: Notification controls (Android 13+)

Supported Shaders

Built-in Effects

• CRT: Classic CRT monitor simulation with curvature and scanlines
• Scanlines: Horizontal scanline overlay effect
• LCD Grid: LCD subpixel pattern simulation
• Passthrough: No effect (transparency only)

Custom Shaders

Place .slangp preset files in assets/shaders/ directory.

Build Requirements

• Android Studio Arctic Fox or later
• Android NDK for native compilation
• Minimum SDK: Android 8.0 (API 26)
• Target SDK: Android 14 (API 34)

Configuration

Performance Modes

• High Quality: Maximum visual fidelity
• Balanced: Optimized for performance and quality
• Battery Saver: Reduced quality for power efficiency

Settings

• Shader selection
• Opacity control (0-100%)
• Performance mode
• FPS limiting
• Auto-start on boot

Technical Implementation

OpenGL ES Setup

setEGLContextClientVersion(2)
setEGLConfigChooser(8, 8, 8, 8, 16, 0)
holder.setFormat(PixelFormat.RGBA_8888)
setZOrderOnTop(true)

Shader Compilation

// Native compilation pipeline
GLSL Source → Preprocessing → Validation → GPU Program

Overlay Window Configuration

WindowManager.LayoutParams().apply {
    type = TYPE_APPLICATION_OVERLAY
    format = PixelFormat.RGBA_8888
    flags = FLAG_NOT_FOCUSABLE or FLAG_NOT_TOUCHABLE or FLAG_HARDWARE_ACCELERATED
    width = MATCH_PARENT
    height = MATCH_PARENT
}

Usage

1. Grant Permissions: Allow overlay permission in system settings
2. Enable Overlay: Toggle overlay switch in main activity
3. Configure Effects: Adjust settings for desired visual effects
4. Performance Tuning: Monitor FPS and adjust performance mode as needed

Limitations

• Works on most apps and games
• Cannot overlay on some system-critical windows (lockscreen, secure dialogs)
• Performance impact varies based on shader complexity and device capabilities
• Some anti-cheat systems may detect overlays

🚀 Getting Started

Download & Install

1. Download APK from Releases
2. Enable unknown sources in Android settings
3. Install the APK and launch the app
4. Grant overlay permission when prompted
5. Choose a shader in settings and enable overlay

Building from Source

git clone https://github.com/mattakins/Shaderlay.git
cd Shaderlay
./gradlew assembleDebug

🤝 Contributing

We welcome contributions! Please see CONTRIBUTING.md for guidelines.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

📋 Roadmap

• Vulkan support for modern devices
• Real-time shader parameter adjustment
• Shader hot-loading from external sources
• Advanced multi-pass shader chains
• Custom shader editor interface
• Performance profiling tools

🐛 Known Issues

• Some anti-cheat systems may detect overlays
• Complex shaders may impact battery life on older devices
• Certain system dialogs cannot be overlaid (security limitation)

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• RetroArch for the slang shader format
• libretro/slang-shaders for shader examples
• Android OpenGL ES documentation and community

📞 Support

• Issues: GitHub Issues
• Discussions: GitHub Discussions

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