Fix for conform with both reference size and fitting size.

Sources/SwiftUISupport/ComponentSwiftUISupport.swift

@@ -22,21 +22,10 @@ private struct ComponentView<C: Component>: View {
     }
 
     var body: some View {
-        let size: CGSize? = bounds.flatMap { bounds in
-            if let referenceSize = component.referenceSize(in: bounds) {
-                return referenceSize
-            }
-
-            return proxy.uiView?.systemLayoutSizeFitting(
-                bounds.size,
-                withHorizontalFittingPriority: .required,
-                verticalFittingPriority: .fittingSizeLevel
-            )
-        }
-
+        let size = preferredSize()
         return ComponentRepresenting(component: component, proxy: proxy)
-            .frame(height: size?.height)
-            .frame(idealWidth: size?.width)
+            .frame(idealWidth: size.idealWidth)
+            .frame(width: size.fixedWidth, height: size.fixedHeight)
             .onAppear { self.proxy.uiView?.contentWillDisplay() }
             .onDisappear { self.proxy.uiView?.contentDidEndDisplay() }
             .background(GeometryReader { geometry in
@@ -46,6 +35,39 @@ private struct ComponentView<C: Component>: View {
     }
 }
 
+@available(iOS 13.0, *)
+extension ComponentView {
+    struct Size {
+        var idealWidth: CGFloat?
+        var fixedWidth: CGFloat?
+        var fixedHeight: CGFloat?
+    }
+
+    func preferredSize() -> Size {
+        if let bounds = bounds, let referenceSize = component.referenceSize(in: bounds) {
+            return Size(
+                fixedWidth: referenceSize.width,
+                fixedHeight: referenceSize.height
+            )
+        }
+        else if let bounds = bounds, let uiView = proxy.uiView {
+            let fittingSize = uiView.systemLayoutSizeFitting(
+                bounds.size,
+                withHorizontalFittingPriority: .required,
+                verticalFittingPriority: .fittingSizeLevel
+            )
+
+            return Size(
+                idealWidth: fittingSize.width,
+                fixedHeight: fittingSize.height
+            )
+        }
+        else {
+            return Size()
+        }
+    }
+}
+
 private struct BoundsPreferenceKey: PreferenceKey {
     static func reduce(value: inout CGRect?, nextValue: () -> CGRect?) {}
 }
@@ -65,16 +87,16 @@ private struct ComponentRepresenting<C: Component>: UIViewRepresentable {
 }
 
 private final class UIComponentView: UIView, ComponentRenderable {
-    @available(*, unavailable)
-    required init?(coder: NSCoder) {
-        fatalError("init(coder:) has not been implemented")
-    }
-
     override init(frame: CGRect) {
         super.init(frame: frame)
 
         backgroundColor = .clear
     }
+
+    @available(*, unavailable)
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
 }
 
 private final class ComponentViewProxy {