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RSLL

ie. RenderSurfaceLayerList

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What’s in a name?

  • RenderSurfaceLayerList

​

  • A list of Layers

​

  • Each layer owns a RenderSurface

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Owns a RenderSurface you say?

  • A RenderSurface represents what will be a offscreen texture or FBO.
  • We draw the subtree below the layer who owns the RenderSurface into the buffer
  • Allows us to apply operations (e.g. opacity) to the entire subtree in one pass.

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Oh, a RenderSurface

Layer

owns

Render Surface

Layer

Layer

Layer

...Subtree...

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What shows up in a RenderSurface?

  • Each RenderSurface has a list of Layers that contribute to the surface.
    • RenderSurface::layer_list()
    • These are the layers that draw content into the surface’s buffer.
  • The layer owning the RenderSurface may or may not contribute to the RenderSurface
    • Depends if the layer draws content at all.

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You’re a contributing layer and you’re a contributing layer...!

Layer

owns

Render Surface

Layer

Layer

Layer

...Subtree...

contributes to

contributes to

contributes to

contributes to

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Then what happens to the Surface?

  • The content in the RenderSurface itself will be drawn into another RenderSurface
    • (except for the root)
  • The layer owning the RenderSurface will itself contribute to another RenderSurface
    • To contribute its RenderSurface content.
    • Regardless of the layer itself drawing anything.

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Ugh, my head.

Layer

owns

Render Surface

...Subtree...

Layer

Layer

Layer

contributes to

contributes to

contributes to

contributes to

Layer

owns

Render Surface

contributes to

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So what does this look like?

  • A layer can contribute to a RenderSurface

​

  • A layer that owns a RenderSurface can contribute to another RenderSurface

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So what does this look like for real?

RSLL

Owns

RS::layer_list()

RootLayer

Surface A

RootLayer

Layer A

Layer B

Layer D

Layer B

Surface B

Layer C

​

​

​

Layers that draw content

Layers that do not draw content

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So then what’s a RenderTarget?

  • RenderTarget of a layer is the layer owning a RenderSurface that the layer contributes to.
    • Layer A owns a RenderSurface.
    • Layer B contributes to Layer A’s RenderSurface.
    • Layer B’s RenderTarget is A.
  • “Target space” refers to the space of the RenderTarget’s RenderSurface.

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Say RenderTarget one more time..

“Target Space”

​

​

​

​

​

Layer

owns

Render Surface

Layer

Layer

Layer

...Subtree...

RenderTarget

RenderTarget

RenderTarget

​

​

​

RenderTarget

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.. I dare you.

  • Most simply:

​

  • The layer’s RenderTarget is the nearest ancestor (including itself) that owns a RenderSurface.

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How do I use this thing?

  • Walking the RSLL is tricky..

​

  • Each layer in layer_list() may be contributing its own content.

​

  • Or maybe it’s contributing the content of the Surface it owns

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Surely there is something simpler

  • Introducing: LayerIterator ♪ trumpet noise ♪
  • Allows you to walk the RSLL in FrontToBack order.
  • At each stop in the iteration, it gives you a Layer, and...
  • One of three states.

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QuantumLayerIterator?

  • Each stop in the LayerIterator is one of:
    • The layer is contributing its own content.
    • The layer owns a RenderSurface and is contributing that.
    • The layer is itself a RenderTarget (owns a RenderSurface)
  • This third state allows you to perform actions on the RenderSurfaces themselves (after dealing with all contributors)

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Ezpz The End

  • gg.

​

  • I’m sure there’s no questions, so why bother asking?