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## Summary
This fixes macOS live-resize behavior for the `eframe`/`egui-wgpu` path
when using the low-latency wgpu surface configuration.
The problem I was seeing is that native window resize can look visibly
below the baseline expected from a desktop GUI: stale or stretched
frames (manifesting as wobble/jitter), or severe lag while dragging a
window edge.
The fix has three parts:
- use `CAMetalLayer.presentsWithTransaction` during live resize to avoid
stale/stretched frames
- temporarily use at least `desired_maximum_frame_latency = 2` while
live resize is active, so transaction presentation does not stall when
the app normally uses `SurfaceConfig::LOW_LATENCY`
- treat macOS `WindowEvent::Moved` as part of the live-resize event
stream, since resizing from the top or left edge changes the window
origin
This PR depends on the winit-side AppKit live-resize timing fix in
[rust-windowing/winit#4588](https://github.com/rust-windowing/winit/pull/4588)
A renderer-only frame-latency change is not enough by itself. The
temporary latency bump only solves the drawable starvation caused by
combining `presentsWithTransaction` with `SurfaceConfig::LOW_LATENCY`.
It does not change when winit emits resize/redraw events, whether
redraws are delivered during AppKit's live-resize event-tracking loop,
or whether the surface size is derived from the current backing rect.
That is why the winit fix is needed first: it makes the windowing layer
report the current AppKit backing size and request redraws from the
live-resize/display callbacks. egui-wgpu still needs this PR on top
because winit does not own the wgpu `Surface` or the underlying
`CAMetalLayer` presentation policy.
In other words: winit fixes when the windowing layer reports
resize/redraw work, while this PR fixes how egui-wgpu presents
Metal-backed wgpu frames during that resize.
## Why change the existing feature?
The existing `macos-window-resize-jitter-fix` feature addresses one
symptom by enabling transaction presentation during resize, but it is
not enough for the low-latency wgpu path.
In particular, `presentsWithTransaction` and
`SurfaceConfig::LOW_LATENCY` interact poorly during AppKit live resize.
The old code avoids that by [skipping transaction presentation when
latency is
`1`](71c4ff3c33/crates/egui-wgpu/src/winit.rs (L417)),
but that means low-latency users get the resize jitter/wobble back.
This PR keeps the low-latency path normally, but temporarily bumps frame
latency only while live resize is active. That gives the resize path
enough drawable slack without changing normal interaction latency.
I removed the `macos-window-resize-jitter-fix` feature because this
seems like the behavior the macOS wgpu path should have by default, not
a separate opt-in. If keeping the feature as a no-op compatibility alias
is preferred, I can adjust the PR.
## Validation
I created a small demo app that somewhat resembles the layout of my
actual app and highlights both horizontal and vertical resize jitter:
- a borderless macOS window
- a simple toolbar
- a scrolling side list
- `SurfaceConfig::LOW_LATENCY`
The toolbar and list make stale or stretched frames easy to see during
native resize. The jitter is visible even on the traffic light buttons.
Recordings:
### Before 1: no transaction presentation, low latency
Shows jitter/wobble and stale/stretched frames during live resize.
https://github.com/user-attachments/assets/2cf4467b-e14c-4f41-8021-0b8c23f41004
### Before 2: transaction presentation with low latency
Shows the other failure mode: live resize can become severely laggy when
transaction presentation is used while keeping
`SurfaceConfig::LOW_LATENCY`.
https://github.com/user-attachments/assets/2f866790-f472-4ede-a3c0-480e8f0f041a
### After: patched egui-wgpu + patched winit, low latency
No visible wobble/jitter and no severe live-resize lag.
https://github.com/user-attachments/assets/59e46e9f-7906-4b5c-a6c7-1d09eae644cd
---------
Co-authored-by: lucasmerlin <hi@lucasmerlin.me>
76 lines
2.7 KiB
TOML
76 lines
2.7 KiB
TOML
[package]
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name = "egui-wgpu"
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version.workspace = true
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description = "Bindings for using egui natively using the wgpu library"
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authors = [
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"Nils Hasenbanck <nils@hasenbanck.de>",
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"embotech <opensource@embotech.com>",
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"Emil Ernerfeldt <emil.ernerfeldt@gmail.com>",
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]
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edition.workspace = true
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rust-version.workspace = true
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homepage = "https://github.com/emilk/egui/tree/main/crates/egui-wgpu"
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license.workspace = true
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readme = "README.md"
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repository = "https://github.com/emilk/egui/tree/main/crates/egui-wgpu"
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categories = ["gui", "game-development"]
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keywords = ["wgpu", "egui", "gui", "gamedev"]
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include = ["../../LICENSE-APACHE", "../../LICENSE-MIT", "**/*.rs", "**/*.wgsl", "Cargo.toml"]
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[lints]
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workspace = true
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[package.metadata.docs.rs]
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all-features = true
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rustdoc-args = ["--generate-link-to-definition"]
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[features]
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default = [
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"fragile-send-sync-non-atomic-wasm",
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"macos-window-resize-jitter-fix",
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"wgpu/default",
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"wgpu/webgl", # A very important fallback for web support
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]
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## Enables the `capture` module for capturing screenshots.
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capture = ["dep:egui"]
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## Enable [`winit`](https://docs.rs/winit) integration. On Linux, requires either `wayland` or `x11`
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winit = ["dep:winit", "winit/rwh_06", "dep:egui", "capture"]
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## Enables Wayland support for winit.
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wayland = ["winit?/wayland"]
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## Enables x11 support for winit.
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x11 = ["winit?/x11"]
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## Make the renderer `Sync` on wasm, exploiting that by default wasm isn't multithreaded.
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## It may make code easier, especially when targeting both native and web.
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## On native most wgpu objects are send and sync, on the web they are not (by nature of the WebGPU specification).
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## This is not supported in [multithreaded WASM](https://gpuweb.github.io/gpuweb/explainer/#multithreading-transfer).
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## Thus that usage is guarded against with compiler errors in wgpu.
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fragile-send-sync-non-atomic-wasm = ["wgpu/fragile-send-sync-non-atomic-wasm"]
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## Enables the macOS live-resize jitter fix, which uses `present_with_transaction`.
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## This requires the `wgpu/metal` backend. Disable this feature if you want to use egui-wgpu
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## with a different backend (e.g. Vulkan or GL) on macOS without pulling in Metal.
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macos-window-resize-jitter-fix = ["wgpu/metal"]
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[dependencies]
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epaint = { workspace = true, default-features = false, features = ["bytemuck"] }
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ahash.workspace = true
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bytemuck.workspace = true
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document-features.workspace = true
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log.workspace = true
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profiling.workspace = true
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thiserror.workspace = true
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type-map.workspace = true
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web-time.workspace = true
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wgpu = { workspace = true, features = ["wgsl"] }
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# Optional dependencies:
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egui = { workspace = true, optional = true, default-features = false }
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winit = { workspace = true, optional = true, default-features = false }
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