Implement Provider Pattern for Changelog Viewers and Split WebView2 Package

[w4po]

Overview

This PR introduces a flexible provider pattern for changelog viewers, splits the WebView2 functionality into a separate package, and adds a new Markdown package for enhanced changelog rendering. These changes improve the modularity, extensibility, and maintainability of the AutoUpdater.NET library.

Features

• Multiple Viewer Options:

  • RichTextBox: Simple text display without HTML rendering
  • WebBrowser: Legacy IE-based browser (fallback option)
  • WebView2: Modern Edge WebView2 for full HTML/CSS support
  • Markdown: GitHub-style Markdown rendering with modern styling

• Content Loading Options:

  • Load from URL (WebBrowser, WebView2, and Markdown)
  • Load direct text content (all viewers)

• User Configuration:

  • Set preferred viewer via AutoUpdater.ChangelogViewerProvider
  • Automatic fallback if the preferred viewer is unavailable
  • Customizable viewer priority system

• Extensibility:

  • Implement IChangelogViewer interface for custom viewers
  • Support for composite viewer pattern

Key Changes

1. Provider Pattern Implementation

• Introduced IChangelogViewerProvider interface for implementing custom changelog viewers
• Created ChangelogViewerFactory to manage and create viewer instances
• Added support for priority-based viewer selection
• Implemented automatic registration of providers through extension loading

2. Package Split

• Moved WebView2-related code to a separate package (AutoUpdater.NET.Official.WebView2)
• Created new Markdown package (AutoUpdater.NET.Official.Markdown)
• Reduced core package dependencies by making WebView2 and Markdown optional
• Added automatic registration of providers through module initialization

3. Markdown Support

• Added GitHub-style Markdown rendering with modern CSS
• Implemented emoji support through Segoe UI Emoji font
• Created composite viewer pattern for flexible rendering options
• Included proper cleanup handling for viewer resources

4. Configuration and Control

• Added AutoLoadExtensions property to control automatic loading of viewer extensions
• Introduced ChangelogViewerProvider property for explicit viewer selection
• Improved error handling with descriptive messages

5. Default Viewers

• Maintained RichTextBox and WebBrowser viewers as default options
• Ensured backward compatibility with existing implementations
• Added proper fallback mechanism when preferred viewers are unavailable

Benefits

1. Modularity: Users can now choose which viewer implementations to include
2. Extensibility: Custom viewers can be easily added through the provider pattern
3. Flexibility: Priority system allows for smart fallback behavior
4. Maintainability: Clear separation of concerns and improved code organization
5. Performance: Optional dependencies reduce the core package size
6. Enhanced Rendering: Modern Markdown support with GitHub-style formatting

Breaking Changes

None. All changes are backward compatible:

• Existing code continues to work without modification
• WebView2 and Markdown functionality available through new packages
• Default viewers maintain their previous behavior

Usage Example

// Disable automatic extension loading if desired
AutoUpdater.AutoLoadExtensions = false;

// Use WebView2 viewer
AutoUpdater.ChangelogViewerProvider = new WebView2ViewerProvider();

// Or use Markdown viewer with default priority
AutoUpdater.ChangelogViewerProvider = new MarkdownViewerProvider();

// Use Markdown viewer with custom priority and viewer
var customViewer = new WebView2Viewer(); // or any IChangelogViewer
AutoUpdater.ChangelogViewerProvider = new MarkdownViewerProvider(customViewer, priority: 3);

// Or let the factory choose the best available viewer

Testing Notes

• Tested with all default viewer implementations
• Verified extension loading mechanism
• Confirmed priority-based selection works as expected
• Validated backward compatibility
• Tested error handling and fallback behavior
• Verified Markdown rendering with various content types

Future Considerations

• Add more built-in viewer implementations

Related Issues

#470 #496 #73 #692