Push window resize and scale factor messages to bevy_window_events

[ProffDea]

I was initially using MessageReader<WindowResized> in my system for my app but once my system grew to use more and more window events, I refactored to using MessageReader<WindowEvent> and matching on its variants. This is where I ran into the issue of the WindowEvent::WindowResized case never matching.

When making this PR, I noticed WindowEvent::WindowBackendScaleFactorChanged and WindowEvent::WindowScaleFactorChanged had the same issue.

Objective

Fixes #15268

Solution

Instead of writing into MessageWriter<WindowResized>, MessageWriter<WindowBackendScaleFactorChanged> and MessageWriter<WindowScaleFactorChanged>, push into bevy_window_events where it gets sent to the forward_bevy_events function for syncing the messages.

Testing

I made local modifications to the window_resizing example to use a MessageReader<WindowEvent> instead of MessageReader<WindowResized> like so:

fn on_resize_system(
    mut text: Single<&mut Text, With<ResolutionText>>,
    mut resize_reader: MessageReader<WindowEvent>,
) {
    for e in resize_reader.read() {
        if let WindowEvent::WindowResized(e) = e {
            // When resolution is being changed
            text.0 = format!("{:.1} x {:.1}", e.width, e.height);
        }
    }
}

I ran this example on linux wayland.

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[alice-i-cecile]

Oh, that explains this bug! Very good fix.

Three things to fix up before we merge:

1. A small omission in the other code path, see comment.
2. setup_react_to_scale_factor_change_test_app should more realistic (it doesn't check WindowEvent).
3. A similar test (or redesigned test) for window resizing.

[kfc35]

Looks good! Thank you for your first contribution 🎊

[alice-i-cecile]

CI failure in https://github.com/bevyengine/bevy/actions/runs/25295357200/job/74153180619 is real. Let us know if you'd like help; this is quite obscure :)

[ProffDea]

Sorry about that, I think it's fixed. Thanks for pointing me in the right direction