macOS window launch behaviour

[Kees-van-Beilen]

Bevy version

0.8.0

[Optional] Relevant system information

• affects all versions of macos

What you did

Running any bevy proccess that launches a window

What went wrong

The window ignores macOS application rules (i.e. floating above fullscreen apps).
It should follow macOS application rules.

Additional information

This is quite an easy fix please make sure that

//the proccess is registered as an sharedApplication
[NSApplication sharedApplication];
//with regular activation policy
[NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
//make key window
[theNSWindowRef makeKeyAndOrderFront:nil];
//and importantly actually activating the process as an app
[NSApp activateIgnoringOtherApps:YES];

[bjorn3]

We don't directly interact with the respective api's. Instead we use winit. I think rust-windowing/winit#2051 describes the same issue as you are having.

[Kees-van-Beilen]

We don't directly interact with the respective api's. Instead we use winit. I think rust-windowing/winit#2051 describes the same issue as you are having.

Well actually winit already made there stance on it so really what you can do and what I would like to see is delay the logic triggered by app.run() until the ApplicationDidFinishLauncing event fires on mac or by registering the activation policy on the current porcess before making the window. This is really Something that has to be fixed because this invites unexpected app behaviour on macos

[Kees-van-Beilen]

There are two ways to fix this:

1. by adding:

#[cfg(target_os = "macos")]
unsafe {
    use cocoa::{appkit::*,base::{NO,nil}};
    let nsapp = NSApp();
    NSApplication::setActivationPolicy_(nsapp, NSApplicationActivationPolicyRegular);
}

to bevy_winit's plugin build functions, or

2. by delaying window creation until the Event::NewEvents(StartCause::Init) has been fired

I'll have to know which one is preferred, than I'll submit a pr with the fix

[mockersf]

To someone not used to cocoa or apple APIs, the code snippet you posted looks a little like dark magic.

I think waiting for the event could be preferred

[MillionIntegrals]

This PR (#5883) seems to be fixing the issue and is live on current main branch. Depending on when the next bevy version is meant to be released, it may be worth to bacport it to a bug fix 0.8.2 release, as current 0.8.1 is quite broken for on macOS.

[mockersf]

0.9 should be in roughly one month.

I'm running on macOS and wouldn't call it quite broken

[maaku]

For what it's worth, @Kees-van-Beilen's suggested code seems quite reasonable. Calling Cocoa from Rust does indeed look like scary unsafe {} black magic, but this call is pretty straight forward. It is simply getting the running process' NSApplication instance and sending it the setActivationPolicy:NSApplicationActivationPolicyRegular message, both of which are technically unsafe operations but should never fail on macOS.