Add UIKitUpdateCycle API

Author: Kyle-Ye

Sources/COpenSwiftUI/Shims/UIKit/UIKit_Private.h

@@ -91,12 +91,52 @@ bool UIViewIgnoresTouchEvents(UIView *view);
 OPENSWIFTUI_EXPORT
 float UIAnimationDragCoefficient(void);
 
+UIView * _UIKitCreateCustomView(Class class, CALayer *layer);
+
 // MARK: - UIUpdate related private API from UIKitCore
 
 OPENSWIFTUI_EXPORT
-bool _UIUpdateAdaptiveRateNeeded();
+bool _UIUpdateAdaptiveRateNeeded(void);
 
-UIView * _UIKitCreateCustomView(Class class, CALayer *layer);
+OPENSWIFTUI_EXPORT
+bool _UIUpdateCycleEnabled(void);
+
+typedef struct _UIUpdateTiming {
+    uint64_t unknown1;
+    uint64_t unknown2;
+    uint64_t unknown3;
+} _UIUpdateTiming;
+
+typedef void (^_UIUpdateSequenceCallback)(void * _Nullable context, CGFloat time, const _UIUpdateTiming * _Nonnull timing);
+
+typedef struct _UIUpdateSequenceItem _UIUpdateSequenceItem;
+
+typedef struct _UIUpdateSequence {
+    _UIUpdateSequenceItem * _Nullable first;
+} _UIUpdateSequence;
+
+typedef struct _UIUpdateSequenceItem {
+    _UIUpdateSequenceItem * _Nullable next;
+    _UIUpdateSequence * _Nullable sequence;
+    const char * name;
+    uint32_t flags;
+    void * _Nullable context;
+    _UIUpdateSequenceCallback _Nullable callback;
+} _UIUpdateSequenceItem;
+
+OPENSWIFTUI_EXPORT
+_UIUpdateSequenceItem * _Nonnull _UIUpdateSequenceCATransactionCommitItem;
+
+OPENSWIFTUI_EXPORT
+void * _Nonnull _UIUpdateSequenceInsertItem(_UIUpdateSequenceItem * _Nullable next,
+                                           _UIUpdateSequence * _Nullable sequence,
+                                           const char * name,
+                                           uint32_t flags,
+                                           void * _Nullable context,
+                                           _UIUpdateSequenceCallback _Nullable callback);
+
+OPENSWIFTUI_EXPORT
+void _UIUpdateSequenceRemoveItem(_UIUpdateSequenceItem *item);
 
 OPENSWIFTUI_ASSUME_NONNULL_END
 

Sources/OpenSwiftUI/Integration/Hosting/UIKit/UIKitUpdateCycle.swift

@@ -0,0 +1,64 @@
+//
+//  UIKitUpdateCycle.swift
+//  OpenSwiftUI
+//
+//  Audited for 6.5.4
+//  Status: WIP
+//  ID: 61722010453917A59567A84BEBF44765 (SwiftUI)
+
+#if os(iOS) || os(visionOS)
+import COpenSwiftUI
+@_spi(ForOpenSwiftUIOnly)
+import OpenSwiftUICore
+
+
+enum UIKitUpdateCycle {
+    private static var observerActions: [() -> Void] = []
+
+    private static var item: OpaquePointer?
+
+    static var defaultUseSetNeedsLayout: Bool = {
+        let key = "UseSetNeedsLayoutForUpdates"
+        let defaults = UserDefaults.standard
+        guard defaults.object(forKey: key) != nil else {
+            return false
+        }
+        return defaults.bool(forKey: key)
+    }()
+
+    static func addPreCommitObserver(_ action: @escaping () -> Void) {
+        guard _UIUpdateCycleEnabled() else {
+            return
+        }
+        if item == nil {
+            item = OpaquePointer(
+                _UIUpdateSequenceInsertItem(
+                    _UIUpdateSequenceCATransactionCommitItem,
+                    nil,
+                    "OpenSwiftUIFlush",
+                    0,
+                    nil,
+                ) { _, _, _ in
+                    let actions = observerActions
+                    guard !actions.isEmpty else { return }
+                    observerActions = []
+                    for action in actions {
+                        Update.perform(action)
+                    }
+                },
+            )
+
+        }
+        observerActions.append(action)
+    }
+
+    static func addPreCommitObserverOrAsyncMain(_ action: @escaping () -> Void) {
+        if _UIUpdateCycleEnabled() {
+            addPreCommitObserver(action)
+        } else {
+            DispatchQueue.main.async(execute: action)
+        }
+    }
+}
+
+#endif

Sources/OpenSwiftUICore/Data/Update.swift

@@ -105,7 +105,7 @@ package enum Update {
 
     @inlinable
     @inline(__always)
-    static func perform<T>(_ body: () throws -> T) rethrows -> T {
+    package static func perform<T>(_ body: () throws -> T) rethrows -> T {
         begin()
         defer { end() }
         return try body()