# Objective
- Since #10702, the way bevy updates the window leads to major slowdowns
as seen in
- #11122
- #11220
- Slow is bad, furthermore, _very_ slow is _very_ bad. We should fix
this issue.
## Solution
- Move the app update code into the `Event::WindowEvent { event:
WindowEvent::RedrawRequested }` branch of the event loop.
- Run `window.request_redraw()` When `runner_state.redraw_requested`
- Instead of swapping `ControlFlow` between `Poll` and `Wait`, we always
keep it at `Wait`, and use `window.request_redraw()` to schedule an
immediate call to the event loop.
- `runner_state.redraw_requested` is set to `true` when
`UpdateMode::Continuous` and when a `RequestRedraw` event is received.
- Extract the redraw code into a separate function, because otherwise
I'd go crazy with the indentation level.
- Fix#11122.
## Testing
I tested the WASM builds as follow:
```sh
cargo run -p build-wasm-example -- --api webgl2 bevymark
python -m http.server --directory examples/wasm/ 8080
# Open browser at http://localhost:8080
```
On main, even spawning a couple sprites is super choppy. Even if it says
"300 FPS". While on this branch, it is smooth as butter.
I also found that it fixes all choppiness on window resize (tested on
Linux/X11). This was another issue from #10702 IIRC.
So here is what I tested:
- On `wasm`: `many_foxes` and `bevymark`, with `argh::from_env()`
commented out, otherwise we get a cryptic error.
- Both with `PresentMode::AutoVsync` and `PresentMode::AutoNoVsync`
- On main, it is consistently choppy.
- With this PR, the visible frame rate is consistent with the diagnostic
numbers
- On native (linux/x11) I ran similar tests, making sure that
`AutoVsync` limits to monitor framerate, and `AutoNoVsync` doesn't.
## Future work
Code could be improved, I wanted a quick solution easy to review, but we
really need to make the code more accessible.
- #9768
- ~~**`WinitSettings::desktop_app()` is completely borked.**~~ actually
broken on main as well
### Review guide
Consider enable the non-whitespace diff to see the _real_ change set.
79021c78c6