Add flag to disable EpoxySwiftUIHostingController keyboard avoidance

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - 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
+- Updated `EpoxySwiftUIHostingController` with a flag to disable its keyboard avoidance behavior
 
 ## [0.10.0](https://github.com/airbnb/epoxy-ios/compare/0.9.0...0.10.0) - 2023-06-29
 

Sources/EpoxyCore/SwiftUI/EpoxySwiftUIHostingController.swift

@@ -19,7 +19,7 @@ open class EpoxySwiftUIHostingController<Content: View>: UIHostingController<Con
 
   /// Creates a `UIHostingController` that optionally ignores the `safeAreaInsets` when laying out
   /// its contained `RootView`.
-  public convenience init(rootView: Content, ignoreSafeArea: Bool) {
+  public convenience init(rootView: Content, ignoreSafeArea: Bool, ignoreKeyboardAvoidance: Bool) {
     self.init(rootView: rootView)
 
     // We unfortunately need to call a private API to disable the safe area. We can also accomplish
@@ -28,6 +28,10 @@ open class EpoxySwiftUIHostingController<Content: View>: UIHostingController<Con
     // available in this file in the `2d28b3181cca50b89618b54836f7a9b6e36ea78e` commit if this API
     // no longer functions in future SwiftUI versions.
     _disableSafeArea = ignoreSafeArea
+
+    if ignoreKeyboardAvoidance {
+      disableKeyboardAvoidance()
+    }
   }
 
   // MARK: Open
@@ -41,5 +45,51 @@ open class EpoxySwiftUIHostingController<Content: View>: UIHostingController<Con
     // below, e.g. to draw highlight states in a `CollectionView`.
     view.backgroundColor = .clear
   }
+
+  /// Creates a dynamic subclass of this hosting controller's view that disables its keyboard
+  /// avoidance behavior.
+  /// Setting `safeAreaRegions` to `.container` also works but cannot be used since it's
+  /// supported on 16.4+ and we need to support older versions.
+  /// See [here](https://steipete.com/posts/disabling-keyboard-avoidance-in-swiftui-uihostingcontroller/) for more info.
+  private func disableKeyboardAvoidance() {
+    guard let viewClass = object_getClass(view) else {
+      EpoxyLogger.shared.assertionFailure("Unable to determine class of \(String(describing: view))")
+      return
+    }
+
+    let viewClassName = class_getName(viewClass)
+    let viewSubclassName = String(cString: viewClassName).appending("_IgnoresKeyboard")
+
+    // If subclass already exists, just set the class of `view` and return.
+    if let subclass = NSClassFromString(viewSubclassName) {
+      object_setClass(view, subclass)
+      return
+    }
+
+    guard let viewSubclassNameUTF8 = (viewSubclassName as NSString).utf8String else {
+      EpoxyLogger.shared.assertionFailure("Unable to get utf8String of \(viewSubclassName)")
+      return
+    }
+    guard let viewSubclass = objc_allocateClassPair(viewClass, viewSubclassNameUTF8, 0) else {
+      EpoxyLogger.shared.assertionFailure(
+        "Unable to subclass \(viewClass) with \(viewSubclassNameUTF8)")
+      return
+    }
+
+    let selector = NSSelectorFromString("keyboardWillShowWithNotification:")
+    guard let method = class_getInstanceMethod(viewClass, selector) else {
+      EpoxyLogger.shared.assertionFailure("Unable to locate method \(selector) on \(viewClass)")
+      objc_disposeClassPair(viewSubclass)
+      return
+    }
+
+    let keyboardWillShowOverride: @convention(block) (AnyObject, AnyObject) -> Void = { _, _ in }
+    let implementation = imp_implementationWithBlock(keyboardWillShowOverride)
+    let typeEncoding = method_getTypeEncoding(method)
+    class_addMethod(viewSubclass, selector, implementation, typeEncoding)
+
+    objc_registerClassPair(viewSubclass)
+    object_setClass(view, viewSubclass)
+  }
 }
 #endif

Sources/EpoxyCore/SwiftUI/EpoxySwiftUIHostingView.swift

@@ -67,7 +67,8 @@ public final class EpoxySwiftUIHostingView<RootView: View>: UIView, EpoxyableVie
     epoxyContent = EpoxyHostingContent(rootView: style.initialContent.rootView)
     viewController = EpoxySwiftUIHostingController(
       rootView: .init(content: epoxyContent, environment: epoxyEnvironment),
-      ignoreSafeArea: true)
+      ignoreSafeArea: true,
+      ignoreKeyboardAvoidance: true)
 
     dataID = style.initialContent.dataID ?? DefaultDataID.noneProvided as AnyHashable
     forceLayoutOnLayoutMarginsChange = style.forceLayoutOnLayoutMarginsChange