Skip releasing displays that are unavailable

[killercup]

Prevent assertion error when trying to close a fullscreen window that was on a display that got disconnected.

---

• Tested on all platforms changed
• Added an entry to the changelog module if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality
• Updated feature matrix, if new features were added or implemented

[killercup]

While investigating bevyengine/bevy#13669 (comment) I saw that there was chance that this method is called with a display handle that relates to a display (monitor) that was disconnected. This led to a panic in the example added in the bevy PR.

[madsmtm]

Noting something that got me confused at first, it's been a while since I read this code: "release" in this context means "release a previously captured display", not "release the resources associated with this pointer" like it usually does.

---

What is the exact assertion error that you get? I'm asking because I'd like to know the error type that you're hitting as the result of CGDisplayRelease?

In any case, it sound like the proper fix instead would be to remove the assertion? And instead error or warning log the result code.

[madsmtm]

What is the exact assertion error that you get? I'm asking because I'd like to know the error type that you're hitting as the result of CGDisplayRelease?

Nvmd, I just saw your logs in the linked Bevy issue, it sounds like you're hitting kCGErrorIllegalArgument? That's weird, could you try to debug-log video_mode?

[killercup]

Thanks for looking at this!

Yeah that's the error code I saw. Here is the full log with a few dbg calls right before the ffi calls -- it doesn't look like it's outputting anything strange, these are the specs for the screen that I disconnect.

2024-06-17T08:13:55.528582Z  INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "MacOS 14.4.1 ", kernel: "23.4.0", cpu: "Apple M1 Pro", core_count: "10", memory: "32.0 GiB" }
2024-06-17T08:13:55.626080Z  INFO bevy_render::renderer: AdapterInfo { name: "Apple M1 Pro", vendor: 0, device: 0, device_type: IntegratedGpu, driver: "", driver_info: "", backend: Metal }
2024-06-17T08:13:56.242942Z  INFO bevy_winit::system: Creating new window "Monitor #41039" (Entity { index: 2, generation: 1 })
2024-06-17T08:13:56.726636Z  INFO bevy_winit::system: Creating new window "Monitor #16901" (Entity { index: 5, generation: 1 })
2024-06-17T08:13:57.045025Z  WARN bevy_time: time_system did not receive the time from the render world! Calculations depending on the time may be incorrect.
2024-06-17T08:14:01.719370Z  INFO bevy_winit::system: Monitor removed Entity { index: 0, generation: 1 }
2024-06-17T08:14:01.749790Z  INFO bevy_winit::system: Closing window Entity { index: 5, generation: 1 }
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1397:17] video_mode = VideoModeHandle {
    size: PhysicalSize {
        width: 5120,
        height: 2160,
    },
    bit_depth: 32,
    refresh_rate_millihertz: 60000,
    monitor: MonitorHandle {
        name: Some(
            "Monitor #16901",
        ),
        native_identifier: 2,
        size: PhysicalSize {
            width: 1,
            height: 1,
        },
        position: PhysicalPosition {
            x: 0,
            y: 0,
        },
        scale_factor: 1.0,
        refresh_rate_millihertz: Some(
            60000,
        ),
        ..
    },
}
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1398:17] video_mode.monitor() = MonitorHandle {
    name: Some(
        "Monitor #16901",
    ),
    native_identifier: 2,
    size: PhysicalSize {
        width: 1,
        height: 1,
    },
    position: PhysicalPosition {
        x: 0,
        y: 0,
    },
    scale_factor: 1.0,
    refresh_rate_millihertz: Some(
        60000,
    ),
    ..
}
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1399:17] video_mode.monitor().native_identifier() = 2
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1400:17] video_mode.monitor() = MonitorHandle {
    name: Some(
        "Monitor #16901",
    ),
    native_identifier: 2,
    size: PhysicalSize {
        width: 1,
        height: 1,
    },
    position: PhysicalPosition {
        x: 0,
        y: 0,
    },
    scale_factor: 1.0,
    refresh_rate_millihertz: Some(
        60000,
    ),
    ..
}
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1401:17] video_mode.native_mode.0 = 0x00000001268378f0
thread 'main' panicked at /Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1407:25:
assertion `left == right` failed
  left: 1001
 right: 0
stack backtrace:
   0: rust_begin_unwind
             at /rustc/9b00956e56009bab2aa15d7bff10916599e3d6d6/library/std/src/panicking.rs:645:5
   1: core::panicking::panic_fmt
             at /rustc/9b00956e56009bab2aa15d7bff10916599e3d6d6/library/core/src/panicking.rs:72:14
   2: core::panicking::assert_failed_inner
   3: core::panicking::assert_failed
             at /rustc/9b00956e56009bab2aa15d7bff10916599e3d6d6/library/core/src/panicking.rs:298:5
   4: winit::platform_impl::platform::window_delegate::WindowDelegate::set_fullscreen
             at /Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1407:25
   5: winit::window::Window::set_fullscreen::{{closure}}
             at /Users/pascal/code/rust-windowing/winit/src/window.rs:1138:50
   6: winit::platform_impl::platform::window::Window::maybe_wait_on_main::{{closure}}
             at /Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window.rs:49:46
   7: objc2_foundation::thread::MainThreadBound<T>::get_on_main::{{closure}}
             at /Users/pascal/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-foundation-0.2.2/src/thread.rs:440:27
   8: objc2_foundation::thread::run_on_main
             at /Users/pascal/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-foundation-0.2.2/src/thread.rs:113:9
   9: objc2_foundation::thread::MainThreadBound<T>::get_on_main
             at /Users/pascal/.cargo/registry/src/index.crates.io-6f17d22bba15001f/objc2-foundation-0.2.2/src/thread.rs:440:9
  10: winit::platform_impl::platform::window::Window::maybe_wait_on_main
             at /Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window.rs:49:9
  11: winit::platform_impl::platform::window::Window::maybe_queue_on_main
             at /Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window.rs:42:9
  12: winit::window::Window::set_fullscreen
             at /Users/pascal/code/rust-windowing/winit/src/window.rs:1138:9
  13: bevy_winit::system::despawn_windows
             at ./crates/bevy_winit/src/system.rs:215:17
  14: core::ops::function::FnMut::call_mut
             at /rustc/9b00956e56009bab2aa15d7bff10916599e3d6d6/library/core/src/ops/function.rs:166:5
  15: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
             at /rustc/9b00956e56009bab2aa15d7bff10916599e3d6d6/library/core/src/ops/function.rs:294:13
  16: <Func as bevy_ecs::system::function_system::SystemParamFunction<fn(F0,F1,F2,F3,F4,F5,F6,F7) .> Out>>::run::call_inner
             at ./crates/bevy_ecs/src/system/function_system.rs:704:21
  17: <Func as bevy_ecs::system::function_system::SystemParamFunction<fn(F0,F1,F2,F3,F4,F5,F6,F7) .> Out>>::run
             at ./crates/bevy_ecs/src/system/function_system.rs:707:17
  18: <bevy_ecs::system::function_system::FunctionSystem<Marker,F> as bevy_ecs::system::system::System>::run_unsafe
             at ./crates/bevy_ecs/src/system/function_system.rs:534:19
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
Encountered a panic in system `bevy_winit::system::despawn_windows`!
Encountered a panic in system `bevy_app::main_schedule::Main::run_main`!

[madsmtm]

Thanks, seems like the CGDirectDisplayID is 2, which definitely sounds like a valid value, and the other CGDisplay functions that we call on it seem to work :/ (I was expecting something like 0).

Could you try running CGDisplayIsCaptured(native_identifier)? You might have to define it first with extern "C" { fn CGDisplayIsCaptured(display: CGDirectDisplayID) -> c_int; }.

Will probably take a closer look myself in a few days when I get the time and have access to an external monitor (especially if reminded). In any case, I still currently think the correct solution is to log the error instead of asserting it.

[killercup]

Sure! I did this now:

+                dbg!(video_mode);
+                dbg!(video_mode.monitor());
+                dbg!(video_mode.monitor().native_identifier());
+                dbg!(video_mode.monitor());
+                dbg!(video_mode.native_mode.0);
+                let available_monitors = monitor::available_monitors();
+                dbg!(available_monitors);
+
+                let monitor = &video_mode.monitor();
+                dbg!(unsafe { CGDisplayIsCaptured(monitor.native_identifier()) });
                 unsafe {
                     ffi::CGRestorePermanentDisplayConfiguration();
                     assert_eq!(
-                        ffi::CGDisplayRelease(video_mode.monitor().native_identifier()),
+                        ffi::CGDisplayRelease(monitor.native_identifier()),
                         ffi::kCGErrorSuccess
                     );
                 };

and it yields

2024-06-17T08:52:20.221625Z  INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "MacOS 14.4.1 ", kernel: "23.4.0", cpu: "Apple M1 Pro", core_count: "10", memory: "32.0 GiB" }
2024-06-17T08:52:20.345355Z  INFO bevy_render::renderer: AdapterInfo { name: "Apple M1 Pro", vendor: 0, device: 0, device_type: IntegratedGpu, driver: "", driver_info: "", backend: Metal }
2024-06-17T08:52:20.935595Z  INFO bevy_winit::system: Creating new window "Monitor #41039" (Entity { index: 2, generation: 1 })
2024-06-17T08:52:21.383400Z  INFO bevy_winit::system: Creating new window "Monitor #16901" (Entity { index: 5, generation: 1 })
2024-06-17T08:52:21.767103Z  WARN bevy_time: time_system did not receive the time from the render world! Calculations depending on the time may be incorrect.
2024-06-17T08:52:26.558842Z  INFO bevy_winit::system: Monitor removed Entity { index: 0, generation: 1 }
2024-06-17T08:52:26.587391Z  INFO bevy_winit::system: Closing window Entity { index: 5, generation: 1 }
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1398:17] video_mode = VideoModeHandle {
    size: PhysicalSize {
        width: 5120,
        height: 2160,
    },
    bit_depth: 32,
    refresh_rate_millihertz: 60000,
    monitor: MonitorHandle {
        name: Some(
            "Monitor #16901",
        ),
        native_identifier: 2,
        size: PhysicalSize {
            width: 1,
            height: 1,
        },
        position: PhysicalPosition {
            x: 0,
            y: 0,
        },
        scale_factor: 1.0,
        refresh_rate_millihertz: Some(
            60000,
        ),
        ..
    },
}
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1399:17] video_mode.monitor() = MonitorHandle {
    name: Some(
        "Monitor #16901",
    ),
    native_identifier: 2,
    size: PhysicalSize {
        width: 1,
        height: 1,
    },
    position: PhysicalPosition {
        x: 0,
        y: 0,
    },
    scale_factor: 1.0,
    refresh_rate_millihertz: Some(
        60000,
    ),
    ..
}
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1400:17] video_mode.monitor().native_identifier() = 2
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1401:17] video_mode.monitor() = MonitorHandle {
    name: Some(
        "Monitor #16901",
    ),
    native_identifier: 2,
    size: PhysicalSize {
        width: 1,
        height: 1,
    },
    position: PhysicalPosition {
        x: 0,
        y: 0,
    },
    scale_factor: 1.0,
    refresh_rate_millihertz: Some(
        60000,
    ),
    ..
}
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1402:17] video_mode.native_mode.0 = 0x000000014194fd30
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1404:17] available_monitors = [
    MonitorHandle {
        name: Some(
            "Monitor #41039",
        ),
        native_identifier: 1,
        size: PhysicalSize {
            width: 3024,
            height: 1964,
        },
        position: PhysicalPosition {
            x: 0,
            y: 0,
        },
        scale_factor: 2.0,
        refresh_rate_millihertz: Some(
            120000,
        ),
        ..
    },
]
[/Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1407:17] unsafe { CGDisplayIsCaptured(monitor.native_identifier()) } = 0
thread 'main' panicked at /Users/pascal/code/rust-windowing/winit/src/platform_impl/macos/window_delegate.rs:1410:21:
assertion `left == right` failed
  left: 1001
 right: 0
stack backtrace: …

Curious how CGDisplayIsCaptured(2) returns no error but available_monitors does not contain that display.