[metal] Do not keep the view around that the surface was created from

We do not need to use it, and the layer itself is already retained, so
it won't be de-allocated from under our feet.

wgpu-hal/src/metal/mod.rs

@@ -367,7 +367,6 @@ pub struct Device {
 }
 
 pub struct Surface {
- view: Option<NonNull<objc::runtime::Object>>,
  render_layer: Mutex<metal::MetalLayer>,
  swapchain_format: RwLock<Option<wgt::TextureFormat>>,
  extent: RwLock<wgt::Extent3d>,

wgpu-hal/src/metal/surface.rs

@@ -63,9 +63,8 @@ impl HalManagedMetalLayerDelegate {
 }
 
 impl super::Surface {
- fn new(view: Option<NonNull<Object>>, layer: metal::MetalLayer) -> Self {
+ fn new(layer: metal::MetalLayer) -> Self {
  Self {
- view,
  render_layer: Mutex::new(layer),
  swapchain_format: RwLock::new(None),
  extent: RwLock::new(wgt::Extent3d::default()),
@@ -85,16 +84,14 @@ impl super::Surface {
  // SAFETY: The layer is an initialized instance of `CAMetalLayer`, and
  // we transfer the retain count to `MetalLayer` using `ManuallyDrop`.
  let layer = unsafe { metal::MetalLayer::from_ptr(layer.cast()) };
- let view: *mut Object = msg_send![view.as_ptr(), retain];
- let view = NonNull::new(view).expect("retain should return the same object");
- Self::new(Some(view), layer)
+ Self::new(layer)
  }
 
  pub unsafe fn from_layer(layer: &metal::MetalLayerRef) -> Self {
  let class = class!(CAMetalLayer);
  let proper_kind: BOOL = msg_send![layer, isKindOfClass: class];
  assert_eq!(proper_kind, YES);
- Self::new(None, layer.to_owned())
+ Self::new(layer.to_owned())
  }
 
  /// Get or create a new `CAMetalLayer` associated with the given `NSView`
@@ -278,16 +275,6 @@ impl super::Surface {
  }
 }
 
-impl Drop for super::Surface {
- fn drop(&mut self) {
- if let Some(view) = self.view {
- unsafe {
- let () = msg_send![view.as_ptr(), release];
- }
- }
- }
-}
-
 impl crate::Surface for super::Surface {
  type A = super::Api;
 
@@ -319,21 +306,23 @@ impl crate::Surface for super::Surface {
 
  // AppKit / UIKit automatically sets the correct scale factor for
  // layers attached to a view. Our layer, however, may not be directly
- // attached to the view; in those cases, we need to set the scale
+ // attached to a view; in those cases, we need to set the scale
  // factor ourselves.
  //
  // For AppKit, we do so by adding a delegate on the layer with the
  // `layer:shouldInheritContentsScale:fromWindow:` method returning
  // `true` - this tells the system to automatically update the scale
  // factor when it changes.
  //
- // For UIKit, we manually update the scale factor here.
+ // For UIKit, we manually update the scale factor from the super layer
+ // here, if there is one.
  //
  // TODO: Is there a way that we could listen to such changes instead?
  #[cfg(not(target_os = "macos"))]
  {
- if let Some(view) = self.view {
- let scale_factor: CGFloat = msg_send![view.as_ptr(), contentScaleFactor];
+ let superlayer: *mut Object = msg_send![render_layer.as_ptr(), superlayer];
+ if !superlayer.is_null() {
+ let scale_factor: CGFloat = msg_send![superlayer, contentsScale];
  let () = msg_send![render_layer.as_ptr(), setContentsScale: scale_factor];
  }
  }