Refresh Queues

A RefreshQueue is Gondwana’s core dirty-region data structure. It is used solely with the CPU-backed BitmapBackbuffer.

Each SceneLayer owns one. It stores world-space rectangles that need to be redrawn.

That detail matters: refresh queues are not screen-space and not adapter-space. They are world-space first.

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What goes into a RefreshQueue

Whenever something changes visually in a layer, the engine can enqueue a world-pixel rectangle representing the affected area.

Examples include:

• sprite motion
• tile changes
• layer-origin changes
• redraw requests caused by camera/view changes
• screen-space overlay invalidation projected back into world space

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What happens next

Later, during rendering, each View converts those world rects into screen-space dirty rectangles for that particular camera/viewport/parallax combination.

That is the key design win: one world-space change can be projected differently by different views.

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Important behavior

• containment checks prevent storing redundant rects
• thread hops are marshaled back to the engine thread
• rendering consumes snapshots of the queue
• queues are cleared after the frame is rendered

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Mental model

RefreshQueue answers: what changed in the world?

The View answers: where does that appear on screen?

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Where to read next

• Gondwana/Rendering/RefreshQueue.cs
• Gondwana/Rendering/RenderSurfaceHost.cs