Engine Architecture Overview

A recommended reading order for getting up to speed on the Gondwana engine codebase quickly.

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🗺️ Reading Order

1. Get the Big Picture First

README.md — Read the whole thing (~5 min). It explains the engine's philosophy (dirty-region rendering, world-space first, code-first design), the runtime flow, and lists all namespaces with their responsibilities. This is the best single document in the repo.

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2. Understand the Host/Lifecycle Contract

Gondwana.Hosting/GameHostBase.cs — The abstract base class for all games. Only ~260 lines, well-documented, and shows the exact lifecycle of a game:

Initialize()
  → ConfigureLogging → InitializeEngine → ConfigurePlatform → ConfigureInput
  → LoadContent → CreateSceneGraph → BindScene → InitializeSceneObjects
  → StartEngine

This tells you every extension point a game author uses before looking at any game-specific code.

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3. Read a Real Demo End-to-End

Demos/Spot/SpotGameHost.cs + Demos/Spot/GameWindow.cs — This is the most complete working game in the repo. Read SpotGameHost to see how a real game wires up assets, scene layers, tilesheets, sprites, audio, input, and particle systems. It subclasses WinFormsGameHost, so you also see a concrete platform adapter in practice.

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4. Understand the Core Engine Loop

Gondwana/Engine.cs — The singleton engine. Read the event declarations (~lines 76–210) to understand the hooks (BeforeBackgroundTasksExecute, BeforeFrameRender, AfterFrameRender, etc.), then skim DoBackgroundTasks and DoForegroundTasks to see what happens every cycle.

Concurrency note: Engine.Start runs the main loop (Cycle / DoForegroundTasks) on a background Task, not the UI thread.

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5. Understand the Rendering Model (3 files, in order)

1. Gondwana/Rendering/RefreshQueue.cs (~95 lines) — The core dirty-region mechanism. Everything that changes enqueues a world-pixel rectangle here. Short, well-commented, and critical to understand.

2. Gondwana/Rendering/Views/View.cs — View = Camera + Viewport. Read the coordinate-conversion methods (ScreenPxToWorldPx, WorldPxToScreenPx, WorldRectToScreenRect, etc.) — this is the math that connects world-space to screen-space. Understanding this file means understanding the rendering model.

3. Gondwana/Rendering/Views/Camera.cs + Viewport.cs — Skim after View.cs to understand camera position/clamping and viewport zoom/offset.

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6. Understand the Scene Graph

Gondwana/Scenes/SceneLayer.cs — The primary data structure for game content. A SceneLayer is a grid of tiles with its own coordinate system, parallax factor, and RefreshQueue. Understanding this explains how sprites, tiles, and parallax backgrounds coexist.

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7. Drawing Primitives (pick what you need)

File/Namespace	What it covers
Gondwana/Drawing/Direct/DirectDrawingManager.cs	Thread-safe manager for overlay drawables (HUD, particles, text)
Gondwana/Drawing/Sprites/	How sprites attach to scene layers and are positioned in world-space
Gondwana/Drawing/Tilesheets/	How image atlases are defined and how sprites reference frame regions

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8. Platform Adapter (WinForms)

Gondwana.WinForms/Rendering/ — Only read if you're working on the host layer. Shows how a WinForms control wraps the SkiaSharp backbuffer and wires up paint/resize events.

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Quick-Reference Mental Model

GameHostBase
  └─ Engine (singleton, loop)
       ├─ Scene
       │    └─ SceneLayer (grid + parallax + RefreshQueue)
       │         └─ SceneLayerTile → Sprite → Tilesheet frame
       ├─ ViewManager
       │    └─ View (Camera + Viewport)  ← world↔screen math lives here
       ├─ DirectDrawingManager           ← HUD/overlays (not in scene grid)
       ├─ Input (Keyboard / Mouse / Gamepad)
       └─ Timers / Collisions

The key insight: state changes call RefreshQueue.AddWorldRect() → the engine's render pass picks it up → View transforms the world rect to screen-space → the platform host repaints only that screen region.