From Hell to Heaven: Porting Doom to MAUI - Nico Vermeir - NDC Oslo 2024

.NET MAUI provides a cross-platform abstraction layer allowing native app development for Android, iOS, Windows, and MacOS from a single codebase

Porting Doom to MAUI revealed several key challenges:

• No direct file system access in sandboxed environment
• Different color handling on Android (R/B values inverted)
• Need for custom touch controls on mobile
• Missing WPF-equivalent bitmap functionality
• Platform-specific keyboard input requirements

SkiaSharp library provided crucial graphics capabilities that MAUI’s built-in 2D library couldn’t handle, particularly for bitmap manipulation

Custom controls and behaviors were needed to:

• Handle touch events and virtual buttons
• Manage platform-specific keyboard input
• Create game control abstractions

Key implementation patterns:

• Using unsafe code blocks for direct pixel manipulation
• Platform-specific code organization in Platforms folder
• Custom event system for game input
• Behavior patterns for cross-platform input handling

Platform considerations:

• Windows version uses WinUI under the hood
• Android/iOS require different input handling
• Performance varies between platforms
• Hardware acceleration limitations

Development approach takeaways:

• Start with working code (WPF) and port incrementally
• Abstract platform-specific functionality
• Focus on core functionality first, then optimize
• Don’t forget the fun factor in development
• Open source collaboration opportunities

Project structure simplified compared to Xamarin:

• Single project instead of multiple platform-specific projects
• Shared codebase with platform-specific overrides
• Resources handling through MAUI’s resource system