Doprez.Stride.Avalonia 1.1.19

Stride.Avalonia

Core bridge library that enables rendering Avalonia UI controls inside the Stride 3D game engine. This is the foundational package — all other packages in this repository depend on it.

How It Works

1. Headless Avalonia — AvaloniaApp.EnsureInitialized<T>() boots Avalonia's headless platform with Skia rendering (no native window). Your AvaloniaApp subclass configures themes and styles.
2. Offscreen pages — AvaloniaPage creates a headless Window, manages frame capture with dirty-tracking, and provides the raw pixel data. Uses reflection to access HeadlessWindowImpl._lastRenderedFrame directly, avoiding LOH allocations from CaptureRenderedFrame().
3. Entity integration — AvaloniaComponent is a Stride EntityComponent that attaches an Avalonia page to an entity. Supports fullscreen overlays and world-space 3D panels.
4. Game system — AvaloniaSystem runs every frame during the Update phase, collecting all AvaloniaComponent instances, forwarding Stride input to Avalonia, and pumping the Avalonia dispatcher.
5. Rendering — AvaloniaSceneRenderer captures each component's Avalonia frame, uploads pixel data to GPU textures, and draws via SpriteBatch (fullscreen) or Sprite3DBatch (world-space).

Features

Rendering Modes

• Fullscreen overlays — auto-resize to the back buffer; drawn as screen-space sprites
• World-space 3D panels — configurable resolution, world size, billboarding, and AABB-based frustum culling
• Depth-sorted rendering — back-to-front ordering for correct alpha blending

Input Forwarding

• Mouse — move, button press/release, scroll wheel, with position deduplication during camera rotation
• Keyboard — key press/release with full modifier support (Shift, Ctrl, Alt)
• Text input — TextInput events forwarded for text field editing
• 3D ray-casting — mouse interaction with world-space panels via ray-cast hit testing
• Smart input skipping — input forwarding is skipped when mouse buttons are held (e.g., during camera rotation)

Texture Atlas System

• Shelf-based texture packer — multiple world-space panels packed into shared atlas textures
• Auto-growth — starts at 1024x1024, grows up to 4096x4096 by doubling and GPU CopyRegion
• Batched draw calls — one draw call per atlas instead of one per panel
• Managed via AvaloniaTextureAtlasManager — handles multiple atlases with O(1) reverse lookup

Performance

• Zero-allocation input bridge — AvaloniaInputBridge uses compiled expression delegates to call PlatformImpl.Input directly, bypassing HeadlessWindowExtensions which runs jobs 20x per event
• Direct framebuffer access — reflection-based shortcut avoids LOH allocations
• Dirty-update throttling — MaxDirtyUpdatesPerFrame on AvaloniaSceneRenderer limits GPU texture uploads per frame

Profiling

• AvaloniaRenderMetrics — singleton tracking per-phase timings (update, input, dispatcher, draw, capture, upload, sprite batch), panel counts, bytes uploaded, GC pressure, and rolling 120-frame history
• AvaloniaProfilingKeys — integration with Stride's built-in profiler overlay
• DebugPanel — ready-to-use Avalonia UserControl displaying FPS, frame time, entity count, draw calls, triangles, memory, uptime, and detailed per-phase Avalonia metrics

Key Classes

Dependencies

Target Framework

net10.0 (cross-platform)

Usage

See the root README for setup instructions and code examples.