simplify DeviceLostClosure by removing its C variant

wgpu-core/src/device/mod.rs

@@ -12,7 +12,6 @@ use crate::{
 
 use arrayvec::ArrayVec;
 use smallvec::SmallVec;
-use std::os::raw::c_char;
 use thiserror::Error;
 use wgt::{BufferAddress, DeviceLostReason, TextureFormat};
 
@@ -183,36 +182,15 @@ impl UserClosures {
             closure();
         }
         for invocation in self.device_lost_invocations {
-            invocation
-                .closure
-                .call(invocation.reason, invocation.message);
+            (invocation.closure)(invocation.reason, invocation.message);
         }
     }
 }
 
 #[cfg(send_sync)]
-pub type DeviceLostCallback = Box<dyn FnOnce(DeviceLostReason, String) + Send + 'static>;
+pub type DeviceLostClosure = Box<dyn FnOnce(DeviceLostReason, String) + Send + 'static>;
 #[cfg(not(send_sync))]
-pub type DeviceLostCallback = Box<dyn FnOnce(DeviceLostReason, String) + 'static>;
-
-pub struct DeviceLostClosureRust {
-    pub callback: DeviceLostCallback,
-}
-
-#[repr(C)]
-pub struct DeviceLostClosureC {
-    pub callback: unsafe extern "C" fn(user_data: *mut u8, reason: u8, message: *const c_char),
-    pub user_data: *mut u8,
-}
-
-#[cfg(send_sync)]
-unsafe impl Send for DeviceLostClosureC {}
-
-pub struct DeviceLostClosure {
-    // We wrap this so creating the enum in the C variant can be unsafe,
-    // allowing our call function to be safe.
-    inner: DeviceLostClosureInner,
-}
+pub type DeviceLostClosure = Box<dyn FnOnce(DeviceLostReason, String) + 'static>;
 
 pub struct DeviceLostInvocation {
     closure: DeviceLostClosure,
@@ -220,46 +198,6 @@ pub struct DeviceLostInvocation {
     message: String,
 }
 
-enum DeviceLostClosureInner {
-    Rust { inner: DeviceLostClosureRust },
-    C { inner: DeviceLostClosureC },
-}
-
-impl DeviceLostClosure {
-    pub fn from_rust(callback: DeviceLostCallback) -> Self {
-        let inner = DeviceLostClosureRust { callback };
-        Self {
-            inner: DeviceLostClosureInner::Rust { inner },
-        }
-    }
-
-    /// # Safety
-    ///
-    /// - The callback pointer must be valid to call with the provided `user_data`
-    ///   pointer.
-    ///
-    /// - Both pointers must point to `'static` data, as the callback may happen at
-    ///   an unspecified time.
-    pub unsafe fn from_c(inner: DeviceLostClosureC) -> Self {
-        Self {
-            inner: DeviceLostClosureInner::C { inner },
-        }
-    }
-
-    pub(crate) fn call(self, reason: DeviceLostReason, message: String) {
-        match self.inner {
-            DeviceLostClosureInner::Rust { inner } => (inner.callback)(reason, message),
-            // SAFETY: the contract of the call to from_c says that this unsafe is sound.
-            DeviceLostClosureInner::C { inner } => unsafe {
-                // Ensure message is structured as a null-terminated C string. It only
-                // needs to live as long as the callback invocation.
-                let message = std::ffi::CString::new(message).unwrap();
-                (inner.callback)(inner.user_data, reason as u8, message.as_ptr())
-            },
-        }
-    }
-}
-
 pub(crate) fn map_buffer(
     buffer: &Buffer,
     offset: BufferAddress,

wgpu-core/src/device/resource.rs

@@ -3600,7 +3600,7 @@ impl Device {
 
         // 1) Resolve the GPUDevice device.lost promise.
         if let Some(device_lost_closure) = self.device_lost_closure.lock().take() {
-            device_lost_closure.call(DeviceLostReason::Unknown, message.to_string());
+            device_lost_closure(DeviceLostReason::Unknown, message.to_string());
         }
 
         // 2) Complete any outstanding mapAsync() steps.

wgpu/src/backend/wgpu_core.rs

@@ -24,7 +24,7 @@ use std::{
     sync::Arc,
 };
 use wgc::error::ContextErrorSource;
-use wgc::{command::bundle_ffi::*, device::DeviceLostClosure, pipeline::CreateShaderModuleError};
+use wgc::{command::bundle_ffi::*, pipeline::CreateShaderModuleError};
 use wgt::WasmNotSendSync;
 
 pub struct ContextWgpuCore(wgc::global::Global);
@@ -1352,9 +1352,8 @@ impl crate::Context for ContextWgpuCore {
         device_data: &Self::DeviceData,
         device_lost_callback: crate::context::DeviceLostCallback,
     ) {
-        let device_lost_closure = DeviceLostClosure::from_rust(device_lost_callback);
         self.0
-            .device_set_device_lost_closure(device_data.id, device_lost_closure);
+            .device_set_device_lost_closure(device_data.id, device_lost_callback);
     }
     fn device_destroy(&self, device_data: &Self::DeviceData) {
         self.0.device_destroy(device_data.id);