b42d2ef4f0
Closes #8326 `check_redraw_requests` switched the event loop to `ControlFlow::Poll` every time it called `request_redraw`, and only ever restored a sleeping control flow when a *timed* repaint was still pending. Once the last scheduled repaint had been consumed the `Poll` was never undone, so the loop kept spinning. This is most visible on Wayland, where `RedrawRequested` is only delivered after the compositor sends a frame callback: between the request and the callback eframe burns 100% of a CPU core, so simply moving the mouse over a reactive app pegs a core. `request_redraw` already wakes the event loop on its own, so the `Poll` is not needed. Drop it, and always set an explicit sleeping control flow at the end of `check_redraw_requests`: `WaitUntil` for the earliest scheduled repaint, `Wait` when nothing is scheduled. **Measured effect of this patch** Two byte-identical eframe apps (a 400-row scrolling page, free-running at 60fps), toggling only whether `eframe` resolves to stock 0.36.0 or this patch. Same machine and session, native Wayland (niri, wgpu/Vulkan). Whole-process CPU is `utime+stime` from `/proc/self/stat`, so it counts every thread — what a system monitor sees. | configuration | whole process | |---|---| | eframe 0.34.3, Wayland | ~12% of a core | | stock 0.36.0, Wayland | **99–100% of a core** | | stock 0.36.0, XWayland (same binary) | ~15% of a core | | **0.36.0 + this patch, Wayland** | **15–16% of a core** | The patch restores the 0.34 baseline and matches the XWayland figure for the same binary — ~6.5× less CPU — with frame delivery unchanged at 60fps. Two details worth noting: the same 0.36 binary is already fine on XWayland, so this isn't application repaint behaviour; and the per-frame *closure* cost rises slightly (1.55 to 2.15 ms) because those frames now run on a CPU that isn't being held at max clocks by the spin loop. * [X] I have followed the instructions in the PR template
eframe: the egui framework
eframe is the official framework library for writing apps using egui. The app can be compiled both to run natively (for Linux, Mac, Windows, and Android) or as a web app (using Wasm).
To get started, see the examples.
To learn how to set up eframe for web and native, go to https://github.com/emilk/eframe_template/ and follow the instructions there!
There is also a tutorial video at https://www.youtube.com/watch?v=NtUkr_z7l84.
For how to use egui, see the egui docs.
eframe defaults to using wgpu for rendering (with an option to change to glow), and on native it uses egui-winit.
To use on Linux, first run:
sudo apt-get install libxcb-render0-dev libxcb-shape0-dev libxcb-xfixes0-dev libxkbcommon-dev libssl-dev
You need to either use edition = "2024", or set resolver = "2" in the [workspace] section of your to-level Cargo.toml. See this link for more info.
You can opt-in to the using egui_glow for rendering by enabling the glow feature and setting NativeOptions::renderer to Renderer::Glow.
Alternatives
eframe is not the only way to write an app using egui! You can also try egui-miniquad, bevy_egui, egui_sdl2_gl, and others.
You can also use egui_glow and winit to build your own app as demonstrated in https://github.com/emilk/egui/blob/main/crates/egui_glow/examples/pure_glow.rs.
Limitations when running egui on the web
eframe and egui compiles to Wasm using either WebGPU (when available) or WebGL2 for rendering, and almost nothing else from the web tech stack. This has some benefits, but also produces some challenges and serious downsides.
- Rendering: Getting pixel-perfect rendering right on the web is very difficult.
- Search: you cannot search an egui web page like you would a normal web page.
- Bringing up an on-screen keyboard on mobile: there is no JS function to do this, so
eframefakes it by adding some invisible DOM elements. It doesn't always work. - Mobile text editing is not as good as for a normal web app.
- No integration with browser settings for colors and fonts.
- Accessibility: There is an experimental screen reader for
eframe, but it has to be enabled explicitly. There is no JS function to ask "Does the user want a screen reader?" (and there should probably not be such a function, due to user tracking/integrity concerns).eguisupports AccessKit, but as of early 2024, AccessKit lacks a Web backend.
In many ways, eframe is trying to make the browser do something it wasn't designed to do (though there are many things browser vendors could do to improve how well libraries like egui work).
The suggested use for eframe are for web apps where performance and responsiveness are more important than accessibility and mobile text editing.
Companion crates
Not all rust crates work when compiled to Wasm, but here are some useful crates have been designed to work well both natively and as Wasm:
Name
The frame in eframe stands both for the frame in which your egui app resides and also for "framework" (eframe is a framework, egui is a library).