Platform/GFX/Surfaces/Use cases

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Use cases for surfaces in Gecko. (Parenthetical list items are optional, but future-looking)


Production by Content:

  • (Producible in workers)
  • (Backbuffer is allocated lazily on any draw/read/query of the backbuffer)
  • (Wait on Fence that prevents early writes to an in-use buffer)
  • Backbuffer is read/writeable at any time during JS execution.
  • 'Present' events cause us to detach the backbuffer frame, create a Fence, and submit it towards the consumer.

Consumption in Compositor:

  • Request the most recently submitted frame (from the producer), and Wait on the Fence to establish frame completeness.
  • (Ability to, instead: Request the most-recently-complete frame, likely polling for frame completion)
  • If new frame retrieved, recycle old frame.
  • (Fence before recycle, so we're sure we're done reading before we begin writing)
  • Frame is considered read-only.
  • Avoid unnecessary readbacks and uploads.
  • Consumed frame persists until overridden by a newer frame. (WebGL can stop producing at any time)

Consumption in Content:

  • (Ability to readback the current frontbuffer? (Can be slow))