Window resizing glitches on MacOS

[UkoeHB]

Bevy version

v0.14.1

[Optional] Relevant system information

MacOS 12.5.1 MacBook Pro

What you did

cargo run --example ui then resized the window.

What went wrong

• When resizing a window, there is a 'banding' effect on the top and right side of the screen where the app is not rendered. This is a regression from v0.13.0, where the banding effect is on the bottom and right side. Banding at the top causes a lot of glitchiness when the rendered panel reverts itself.
• If using desktop_app() window mode, the window does not update immediately after a resize despite receiving a resize event (presumably).

Additional information

I bisected the problem to the PR introducing winit v0.30. It has persisted until now despite #14609 claiming to fix it. See #14255 as a duplicate issue that was closed.

Attached is a video of the problem, showcasing both the top/right banding and the delay (this is cargo run --example ui_wrap_debug, which uses desktop_app() window mode):

bevy_ui_resize_bug_08_31_24.mp4

There is currently an open wgpu PR that fixes part of the problem. However, it doesn't explain the regression from bottom/right banding to top/right banding. I ran the hello_triangle example on wgpu v0.19.3 and got bottom/right banding as expected.

One thing I noticed is we are not calling request_redraw() on the winit window when WindowEvent::Resized is received, even though winit says you need to do so. Unfortunately, adding it manually did not seem to help much.

[madsmtm]

bottom/right banding to top/right banding

Might be rust-windowing/winit#3302, Winit now sets isFlipped on NSViews to match it's coordinate system, might have had unintended consequences for downstream consumers?

[UkoeHB]

@madsmtm hey seems a likely culprit. What would be needed to fix the issue in bevy?

[madsmtm]

No idea, not experienced enough with Bevy to know how they do their rendering. In any case, you could start by trying to use a patched version of Winit with isFlipped set to false so see if that's even the issue?

[UkoeHB]

This seems to be better now, although still not perfect.