Fix timing of layout margin layout invalidation for bars (#168)

* Fix timing of layout margin layout invalidation for bars

* Update CHANGELOG.md

Co-authored-by: Bryn Bodayle <[email protected]>

* Update EpoxySwiftUIHostingView.swift

---------

Co-authored-by: Bryn Bodayle <[email protected]>

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  unexpected dimensions
 - Made new layout-based SwiftUI cell rendering option the default.
 - Fixed interaction of SwiftUI bars on visionOS
+- Added flag for forcing layout on a hosted SwiftUI view after layout margins change
 
 ## [0.10.0](https://github.com/airbnb/epoxy-ios/compare/0.9.0...0.10.0) - 2023-06-29
 

Sources/EpoxyBars/BarModel/SwiftUI.View+BarModel.swift

@@ -21,6 +21,7 @@ extension View {
  content: .init(rootView: self, dataID: dataID),
  style: .init(
  reuseBehavior: reuseBehavior,
+ forceLayoutOnLayoutMarginsChange: true,
  initialContent: .init(rootView: self, dataID: dataID)))
  .linkDisplayLifecycle()
  }

Sources/EpoxyCollectionView/Models/ItemModel/SwiftUI.View+ItemModel.swift

@@ -21,6 +21,7 @@ extension View {
  content: .init(rootView: self, dataID: dataID),
  style: .init(
  reuseBehavior: reuseBehavior,
+ forceLayoutOnLayoutMarginsChange: false,
  initialContent: .init(rootView: self, dataID: dataID)))
  .linkDisplayLifecycle()
  }

Sources/EpoxyCollectionView/Models/SupplementaryItemModel/SwiftUI.View+SupplementaryItemModel.swift

@@ -21,6 +21,7 @@ extension View {
  content: .init(rootView: self, dataID: dataID),
  style: .init(
  reuseBehavior: reuseBehavior,
+ forceLayoutOnLayoutMarginsChange: false,
  initialContent: .init(rootView: self, dataID: dataID)))
  .linkDisplayLifecycle()
  }

Sources/EpoxyCore/SwiftUI/EpoxySwiftUIHostingView.swift

@@ -70,6 +70,7 @@ public final class EpoxySwiftUIHostingView<RootView: View>: UIView, EpoxyableVie
  ignoreSafeArea: true)
 
  dataID = style.initialContent.dataID ?? DefaultDataID.noneProvided as AnyHashable
+ forceLayoutOnLayoutMarginsChange = style.forceLayoutOnLayoutMarginsChange
 
  super.init(frame: .zero)
 
@@ -97,20 +98,33 @@ public final class EpoxySwiftUIHostingView<RootView: View>: UIView, EpoxyableVie
  // MARK: Public
 
  public struct Style: Hashable {
- public init(reuseBehavior: SwiftUIHostingViewReuseBehavior, initialContent: Content) {
+
+ // MARK: Lifecycle
+
+ public init(
+ reuseBehavior: SwiftUIHostingViewReuseBehavior,
+ forceLayoutOnLayoutMarginsChange: Bool,
+ initialContent: Content)
+ {
  self.reuseBehavior = reuseBehavior
+ self.forceLayoutOnLayoutMarginsChange = forceLayoutOnLayoutMarginsChange
  self.initialContent = initialContent
  }
 
+ // MARK: Public
+
  public var reuseBehavior: SwiftUIHostingViewReuseBehavior
+ public var forceLayoutOnLayoutMarginsChange: Bool
  public var initialContent: Content
 
  public static func == (lhs: Style, rhs: Style) -> Bool {
- lhs.reuseBehavior == rhs.reuseBehavior
+ lhs.reuseBehavior == rhs.reuseBehavior &&
+ lhs.forceLayoutOnLayoutMarginsChange == rhs.forceLayoutOnLayoutMarginsChange
  }
 
  public func hash(into hasher: inout Hasher) {
  hasher.combine(reuseBehavior)
+ hasher.combine(forceLayoutOnLayoutMarginsChange)
  }
  }
 
@@ -212,10 +226,22 @@ public final class EpoxySwiftUIHostingView<RootView: View>: UIView, EpoxyableVie
  trailing: margins.right)
  }
 
- // Allow the layout margins update to fully propagate through to the SwiftUI View before
- // invalidating the layout.
- DispatchQueue.main.async {
- self.viewController.view.invalidateIntrinsicContentSize()
+ if forceLayoutOnLayoutMarginsChange {
+ // If we don't force a layout pass and size invalidation synchronously after the layout
+ // margins change, it's possible for the hosting view to render with incorrect margins,
+ // causing a visual jump as the layout resolves over multiple runloop iterations. This seems
+ // to be more common with top and bottom bars, since they can be laid out early during view
+ // controller transitions. If this works well, we may make this the default behavior for all
+ // SwiftUI views.
+ viewController.view.setNeedsLayout()
+ viewController.view.layoutIfNeeded()
+ viewController.view.invalidateIntrinsicContentSize()
+ } else {
+ // Allow the layout margins update to fully propagate through to the SwiftUI View before
+ // invalidating the layout.
+ DispatchQueue.main.async {
+ self.viewController.view.invalidateIntrinsicContentSize()
+ }
  }
  }
 
@@ -236,6 +262,7 @@ public final class EpoxySwiftUIHostingView<RootView: View>: UIView, EpoxyableVie
  private let viewController: EpoxySwiftUIHostingController<EpoxyHostingWrapper<RootView>>
  private let epoxyContent: EpoxyHostingContent<RootView>
  private let epoxyEnvironment = EpoxyHostingEnvironment()
+ private let forceLayoutOnLayoutMarginsChange: Bool
  private var dataID: AnyHashable
  private var state: AppearanceState = .disappeared