[Performance] Streamline SwiftUI size observation

AsyncImageView/AsyncSwiftUIImageView.swift

@@ -58,12 +58,11 @@ Renderer.RenderResult == PlaceholderRenderer.RenderResult {
     public var body: some View {
         ZStack {
             self.imageView
-
-            Color.clear
-                .modifier(SizeModifier())
-                .onPreferenceChange(ImageSizePreferenceKey.self) { imageSize in
-                    self.size = imageSize
-                }
+        }
+        .onGeometryChange(for: CGSize.self) { geometry in
+            geometry.size
+        } action: { imageSize in
+            self.size = imageSize
         }
         .onAppear {
             self.viewModel.start()
@@ -110,27 +109,6 @@ public extension AsyncSwiftUIImageView {
     }
 }
 
-private struct ImageSizePreferenceKey: PreferenceKey {
-    typealias Value = CGSize
-
-    static var defaultValue: CGSize = .zero
-
-    static func reduce(value: inout CGSize, nextValue: () -> CGSize) {
-        value = nextValue()
-    }
-}
-
-private struct SizeModifier: ViewModifier {
-    func body(content: Content) -> some View {
-        content.background(
-            GeometryReader { geometry in
-                Color.clear
-                    .preference(key: ImageSizePreferenceKey.self, value: geometry.size)
-            }
-        )
-    }
-}
-
 @Observable
 private final class AsyncSwiftUIImageViewModel<
     Data: RenderDataType,

AsyncImageViewTests/AsyncSwiftUIImageViewSpec.swift

@@ -0,0 +1,59 @@
+import Quick
+import Nimble
+import SwiftUI
+import UIKit
+
+import ReactiveSwift
+
+import AsyncImageView
+
+class AsyncSwiftUIImageViewSpec: QuickSpec {
+    override class func spec() {
+        describe("AsyncSwiftUIImageView") {
+            it("requests the full proposed size") {
+                let renderer = SquareImageRenderer()
+                typealias ViewType = AsyncSwiftUIImageView<
+                    TestRenderData,
+                    TestData,
+                    SquareImageRenderer,
+                    SquareImageRenderer
+                >
+                let view = ViewType(
+                    renderer: renderer,
+                    placeholderRenderer: nil,
+                    uiScheduler: ImmediateScheduler(),
+                    imageCreationScheduler: ImmediateScheduler()
+                )
+                .data(.a)
+                .frame(width: 300, height: 100)
+                let viewController = UIHostingController(rootView: view)
+                let window = UIWindow(frame: CGRect(origin: .zero, size: CGSize(width: 300, height: 100)))
+                window.rootViewController = viewController
+                window.makeKeyAndVisible()
+                viewController.view.frame = window.bounds
+                viewController.view.layoutIfNeeded()
+
+                let expectedRequest = TestRenderData(data: .a, size: window.bounds.size)
+                expect(renderer.renderedImages.value).toEventually(equal([expectedRequest]))
+
+                RunLoop.current.run(until: Date(timeIntervalSinceNow: 0.1))
+                viewController.view.layoutIfNeeded()
+
+                expect(renderer.renderedImages.value) == [expectedRequest]
+            }
+        }
+    }
+}
+
+private final class SquareImageRenderer: RendererType {
+    let renderedImages = Atomic<[TestRenderData]>([])
+
+    func renderImageWithData(_ data: TestRenderData) -> SignalProducer<UIImage, Never> {
+        TestRenderer.rendererForSize(CGSize(width: 100, height: 100), scale: 1)
+            .asyncRenderer(ImmediateScheduler())
+            .renderImageWithData(data)
+            .on(started: {
+                self.renderedImages.modify { $0.append(data) }
+            })
+    }
+}