Use IOSurface on macOS/iOS
#329
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madsmtm
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enhancement
madsmtm
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Jan 31, 2026
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| // Block until back buffer is no longer being used by the compositor. | ||
| // | ||
| // TODO: Allow configuring this: https://github.com/rust-windowing/softbuffer/issues/29 | ||
| // TODO: Is this actually the check we want to do? It seems like the compositor doesn't | ||
| // properly set the usage state when the application loses focus, even if you continue | ||
| // rendering there? | ||
| // | ||
| // Should we instead set up a `CVDisplayLink`, and only allow using the back buffer once a | ||
| // certain number of frames have passed since it was presented? Would be better though not | ||
| // perfect, `CVDisplayLink` isn't guaranteed to actually match the display's refresh rate: | ||
| // https://developer.apple.com/library/archive/documentation/GraphicsImaging/Conceptual/CoreVideo/CVProg_Concepts/CVProg_Concepts.html#//apple_ref/doc/uid/TP40001536-CH202-DontLinkElementID_2 | ||
| // | ||
| // Another option would be to keep a boundless queue as described in: | ||
| // https://github.com/commercial-emacs/commercial-emacs/blob/68f5a28a316ea0c553d4274ce86e95fc4a5a701a/src/nsterm.m#L10552-L10571 | ||
| while self.back.surface.is_in_use() { | ||
| std::thread::yield_now(); | ||
| } |
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The way we wait for the compositor to stop using the buffer(s) here is kinda bad, but that can be resolved later, and shouldn't be a problem for applications that either:
- Only re-render when something changes.
- Do proper frame-pacing (Winit doesn't yet provide that though).
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Write directly into a shared memory buffer that can be shared directly with the compositor and avoids copying bytes when presenting (QuartzCore was copying stuff before). This also implements double and triple buffering of the surface, to avoid creating a bunch of unnecessary buffers. The compositor seems to sometimes work on two buffers at the same time? A bit unsure why. The way we wait for the compositor to stop using the buffer(s) is kinda bad, but that can be resolved later, and shouldn't be a problem for applications that do proper frame-pacing (which Winit doesn't yet provide though).
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Make
Buffer<'_>be backed by a shared memory buffer that can be shared directly with the compositor. This makes the CoreGraphics backend zero-copy (QuartzCore was copying from theCGImageProviderinternally before when committing the transaction).This also implements triple buffering of the surface, to avoid creating a bunch of unnecessary buffers. The compositor seems to want to work on two buffers at the same time? A bit unsure why, but I know that we do get tearing if we try to touch things while it's working on it.
Fixes #83.
This requires #321, because
IOSurfacedoes not support RGBX (so the alpha channel must be opaque to render correctly).Tested on:
Replaces #95 and #96.