How to Build a Custom Frontend with Roms Launcher .NETRoms Launcher .NET is a flexible, open-source frontend framework for organizing and launching games from ROM collections. Building a custom frontend allows you to tailor the UI, metadata presentation, controls, and automation to your personal setup — whether you’re building a dedicated arcade cabinet, a media-center PC, or a multi-platform emulator hub. This guide walks through planning, setting up the development environment, creating a custom theme and layout, integrating metadata and artwork, handling controller and input mapping, adding automation and scripts, and packaging and deploying your frontend.
Prerequisites
- Basic knowledge of C# and .NET (Core/.NET 6+)
- Familiarity with XAML/WPF or Avalonia UI (Roms Launcher .NET supports multiple UI backends; check the version you’re targeting)
- Installed Roms Launcher .NET source or binaries
- Emulators configured on your system
- A working ROM collection organized by platform
- Optional: experience with image editing (for artwork), SQLite (for metadata), and PowerShell/Bash (for scripts)
1. Plan Your Frontend
Before coding, decide what your frontend should do and look like:
- Target device (PC, Raspberry Pi, arcade cabinet)
- UI style: grid, list, carousel, or mixed
- Required features: search, filters, favorites, playlists, controller support, themes
- Metadata and assets: screenshots, box art, descriptions, release year, developer
- Automation needs: auto-launch scripts, ROM verification, scraping
Make a sketch or mockup of the main screens: library, game details, settings, and now-playing.
2. Set Up the Development Environment
- Clone or download the Roms Launcher .NET repository (or get the latest SDK/binaries).
- Install .NET SDK (recommended .NET 7 or later unless project specifies otherwise).
- Choose UI framework:
- WPF (Windows-only): good for native Windows look and performance.
- Avalonia: cross-platform (Windows, Linux, macOS) and similar XAML syntax.
- Install an IDE: Visual Studio, Visual Studio Code + C# extensions, or JetBrains Rider.
- Restore NuGet packages and build the solution to confirm environment is working.
Example commands:
git clone https://github.com/your-fork/roms-launcher-dotnet.git cd roms-launcher-dotnet dotnet restore dotnet build 3. Project Structure and Extensibility Points
Understand where to plug in your custom frontend:
- Main application project: hosts app lifecycle, navigation, and window.
- ViewModels: handle data binding, commands, and logic.
- Views/XAML: UI layout and styles.
- Services: metadata provider, asset loader, emulator launcher, input service.
- Plugins or modules: some builds support plug-in architecture for features.
Look for:
- Interfaces like IGameService, IMetadataService, ILauncherService.
- Dependency injection container (Microsoft.Extensions.DependencyInjection) setup.
- Resource dictionaries and style/theme files.
4. Designing the UI
A good frontend separates presentation from logic via MVVM. Key screens:
- Library/Grid View
- Thumbnail, title, platform, favorite icon
- Virtualized lists for performance (e.g., VirtualizingStackPanel, ItemsRepeater)
- Game Details
- Large box art/screenshot carousel, description, metadata table, play button
- Settings
- Emulator paths, input mapping, themes, scraping options
- Now Playing / Launch Overlay
- Show emulator launch progress and “Return to frontend” mechanism
Tips:
- Use data templates for platform-specific presentation.
- Optimize image loading: cache thumbnails, load full images asynchronously.
- Support multiple themes via resource dictionaries (light/dark, arcade/cabinet).
5. Handling Metadata and Artwork
Good metadata makes a frontend feel polished.
- Metadata sources:
- Built-in XML/CSV
- Emumovies/ScreenScraper or custom scrapers
- Local database (SQLite) or JSON files
- Implement or adapt an IMetadataService to:
- Query by ROM filename, CRC, or game name
- Normalize platform names and release dates
- Artwork management:
- Cache thumbnails and full-resolution images in a predictable folder structure (e.g., /cache/platform/title/)
- Use background workers to pre-fetch images for smooth browsing
- Provide fallback images for missing assets
Example cache path pattern:
/Cache/{Platform}/{ROMName}/{type}.png 6. Input and Controller Support
Controller handling is critical for a seamless experience.
- Abstract input via an IInputService that maps controller inputs to frontend navigation (UI up/down/select) and to emulator passthrough.
- Support hotkeys and long-press actions (e.g., hold Select + Start to exit emulator).
- Use libraries:
- SharpDX/XInput for Xbox controllers on Windows
- SDL2# or SDL2-CS for cross-platform controller handling
- Provide a UI for mapping controls, saving profiles per controller.
Example mapping UI features:
- Auto-detect controller
- Prompt user to press buttons for mapping
- Save profiles per emulator or platform
7. Launching Emulators
A robust ILauncherService should:
- Validate emulator executable path and command-line arguments
- Support per-game overrides (e.g., using specific cores or launch parameters)
- Handle asynchronous process launching and monitor exit codes
- Optionally suspend frontend audio/video and mute background processes
- Provide a graceful return flow (restore frontend state, refresh play count)
Basic launch sequence:
- Resolve emulator and ROM path
- Build command-line with arguments/paths
- Start process and optionally wait for exit
- Restore frontend UI when emulator closes
Example C# snippet:
var startInfo = new ProcessStartInfo { FileName = emulatorPath, Arguments = $""{romPath}" {extraArgs}", UseShellExecute = false }; var proc = Process.Start(startInfo); await proc.WaitForExitAsync(); 8. Automation, Scripting, and Plugins
Add power features:
- Pre-launch checks: verify ROM checksum, unzip archives, apply patches
- Post-launch hooks: increment playcount, update last-played timestamp
- Scheduled tasks: nightly scraping, backup metadata
- Plugin architecture: allow third-party extensions to add scrapers, themes, or social sharing
Script examples:
- PowerShell or Bash scripts to move ROMs into organized folders
- JSON-configured automation rules to run pre/post tasks
9. Performance and Optimization
- Virtualize lists and defer image loading.
- Use asynchronous I/O for disk and network operations.
- Employ simple in-memory caching for frequently accessed metadata.
- Avoid heavy UI work on the UI thread — use Task.Run or background workers.
- Profile startup and identify slow services (e.g., large scrapers).
10. Packaging and Deployment
- Build release artifacts for the target platform(s).
- Create an installer (NSIS, Inno Setup) for Windows or package formats for Linux (AppImage, .deb) and macOS (zip/.app).
- Include a settings migration path for users upgrading from older versions.
- Document how to install emulators and configure paths.
11. Testing and QA
- Test with multiple controller types and multiple emulator backends.
- Validate behavior with missing artwork and corrupted ROMs.
- Run performance tests on target hardware (e.g., Raspberry Pi).
- Add logging and telemetry (local-only, opt-in) to capture crashes and errors.
12. Example: Minimal Custom Grid Frontend (Overview)
- Create a new WPF/Avalonia project.
- Implement GameViewModel with properties: Title, Platform, ThumbnailPath, RomPath.
- Bind an ItemsControl to an ObservableCollection
. - Implement commands for Play, Favorite, and Info.
- Implement a simple ILauncherService to start the emulator process.
13. Resources and Further Reading
- Roms Launcher .NET repository and documentation
- Emulator CLI docs (RetroArch, MAME, PCSX2, etc.)
- Scraper APIs and artwork galleries (Emumovies, ScreenScraper)
If you want, I can: provide a starter project template (WPF or Avalonia), generate example ViewModel/View code, or draft a sample ILauncherService implementation. Which would you like?
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