Address #661 issue since v2.8.0 (#662)

See this comment for more details.
#661 (comment)

Author: scenee

Examples/Samples/Sources/PanelLayouts.swift

@@ -76,3 +76,18 @@ class ModalPanelLayout: FloatingPanelLayout {
         return 0.3
     }
 }
+
+class ModalPanelLayout2: FloatingPanelLayout {
+    let position: FloatingPanelPosition = .bottom
+    let initialState: FloatingPanelState = .half
+    var anchors: [FloatingPanelState: FloatingPanelLayoutAnchoring] {
+        [
+            .full: FloatingPanelLayoutAnchor(fractionalInset: 0.0, edge: .top, referenceGuide: .superview),
+            .half: FloatingPanelLayoutAnchor(fractionalInset: 0.5, edge: .bottom, referenceGuide: .superview)
+        ]
+    }
+    func backdropAlpha(for _: FloatingPanelState) -> CGFloat {
+        0.6
+    }
+}
+

Examples/Samples/Sources/UseCases/UseCase.swift

@@ -9,6 +9,7 @@ enum UseCase: Int, CaseIterable {
     case showDetail
     case showModal
     case showPanelModal
+    case showPanelModal2
     case showMultiPanelModal
     case showPanelInSheetModal
     case showOnWindow
@@ -39,6 +40,7 @@ extension UseCase {
         case .showDetail: return "Show Detail Panel"
         case .showModal: return "Show Modal"
         case .showPanelModal: return "Show Panel Modal"
+        case .showPanelModal2: return "Show Panel Modal 2"
         case .showMultiPanelModal: return "Show Multi Panel Modal"
         case .showOnWindow: return "Show Panel over Window"
         case .showPanelInSheetModal: return "Show Panel in Sheet Modal"
@@ -81,10 +83,11 @@ extension UseCase {
         case .trackingTextView: return .storyboard("ConsoleViewController") // Storyboard only
         case .showDetail: return .storyboard(String(describing: DetailViewController.self))
         case .showModal: return .storyboard(String(describing: ModalViewController.self))
+        case .showPanelModal: return .viewController(DebugTableViewController())
+        case .showPanelModal2: return .storyboard("ConsoleViewController")
         case .showMultiPanelModal: return .viewController(DebugTableViewController())
         case .showOnWindow: return .viewController(DebugTableViewController())
         case .showPanelInSheetModal: return .viewController(DebugTableViewController())
-        case .showPanelModal: return .viewController(DebugTableViewController())
         case .showTabBar: return .storyboard(String(describing: TabBarViewController.self))
         case .showPageView: return .viewController(DebugTableViewController())
         case .showPageContentView: return .viewController(DebugTableViewController())

Examples/Samples/Sources/UseCases/UseCaseController.swift

@@ -178,6 +178,14 @@ extension UseCaseController {
 
             mainVC.present(fpc, animated: true, completion: nil)
 
+        case .showPanelModal2:
+            let fpc = FloatingPanelController()
+            fpc.set(contentViewController: contentVC)
+            fpc.delegate = self
+            fpc.track(scrollView: (contentVC as? DebugTextViewController)!.textView)
+
+            mainVC.present(fpc, animated: true, completion: nil)
+
         case .showMultiPanelModal:
             let fpc = MultiPanelController()
             mainVC.present(fpc, animated: true, completion: nil)
@@ -435,6 +443,8 @@ extension UseCaseController: FloatingPanelControllerDelegate {
             return newCollection.verticalSizeClass == .compact ? RemovablePanelLandscapeLayout() :  RemovablePanelLayout()
         case .showIntrinsicView:
             return IntrinsicPanelLayout()
+        case .showPanelModal2:
+            return ModalPanelLayout2()
         case .showPanelModal:
             if vc != mainPanelVC && vc != detailPanelVC {
                 return ModalPanelLayout()

Sources/Core.swift

@@ -1197,16 +1197,21 @@ class Core: NSObject, UIGestureRecognizerDelegate {
         return state == layoutAdapter.mostExpandedState
     }
 
-    /// Adjust content inset of the tracking scroll view if the controller's
-    /// `contentInsetAdjustmentBehavior` is `.always` and its `contentMode` is `.static`.
-    /// if its content is scrollable, the content might not be fully visible on `.half`
-    /// state, for example. Therefore the content inset needs to adjust to display the
-    /// full content.
+    // Adjusts content inset of the tracking scroll view when the following conditions are met:
+    // - The controller's `contentInsetAdjustmentBehavior` is `.always`
+    // - Its `contentMode` is `.static`
+    // - Its content is scrollable
+    // This ensures that the content remains fully visible in intermediate states like `.half`,
+    // by using `UIScrollView.safeAreaInsets` and the panel's current position.
+    // This method must not be invoked in the fully expanded state, as it may lead to unexpected
+    // behavior under the top safe area (i.e., the status bar).
     func adjustScrollContentInsetIfNeeded() {
         guard
             let fpc = ownerVC,
             let scrollView = scrollView,
-            fpc.contentInsetAdjustmentBehavior == .always
+            fpc.contentInsetAdjustmentBehavior == .always,
+            fpc.state != layoutAdapter.mostExpandedState,
+            isScrollable(state: fpc.state)
         else { return }
 
         switch fpc.contentMode {

Tests/CoreTests.swift

@@ -863,11 +863,18 @@ class CoreTests: XCTestCase {
                 customSafeAreaInsets
             }
         }
+        class PanelDelegate: FloatingPanelControllerDelegate {
+            func floatingPanel(_ fpc: FloatingPanelController, shouldAllowToScroll scrollView: UIScrollView, in state: FloatingPanelState) -> Bool {
+                return state == .full || state == .half
+            }
+        }
+        let delegate = PanelDelegate()
 
         do {
             let scrollView = CustomScrollView()
             scrollView.customSafeAreaInsets = UIEdgeInsets(top: 0, left: 0, bottom: 34, right: 0)
             let fpc = FloatingPanelController()
+            fpc.delegate = delegate
             fpc.track(scrollView: scrollView)
             fpc.layout = FloatingPanelBottomLayout()
             fpc.contentInsetAdjustmentBehavior = .always
@@ -894,6 +901,7 @@ class CoreTests: XCTestCase {
             let scrollView = CustomScrollView()
             scrollView.customSafeAreaInsets = UIEdgeInsets(top: 91, left: 0, bottom: 0, right: 0)
             let fpc = FloatingPanelController()
+            fpc.delegate = delegate
             fpc.track(scrollView: scrollView)
             fpc.layout = FloatingPanelTopPositionedLayout()
             fpc.contentInsetAdjustmentBehavior = .always
@@ -916,6 +924,40 @@ class CoreTests: XCTestCase {
         }
     }
 
+    func test_adjustScrollContentInsetIfNeeded_normal() {
+        class CustomScrollView: UIScrollView {
+            var customSafeAreaInsets: UIEdgeInsets = .zero
+            override var safeAreaInsets: UIEdgeInsets {
+                customSafeAreaInsets
+            }
+        }
+        do {
+            let scrollView = CustomScrollView()
+            scrollView.customSafeAreaInsets = UIEdgeInsets(top: 42, left: 0, bottom: 34, right: 0)
+            let fpc = FloatingPanelController()
+            fpc.track(scrollView: scrollView)
+            fpc.layout = FloatingPanelBottomLayout()
+            fpc.contentInsetAdjustmentBehavior = .always
+            fpc.contentMode = .static
+            fpc.showForTest()
+
+            fpc.move(to: .half, animated: false)
+            fpc.floatingPanel.adjustScrollContentInsetIfNeeded()
+
+            XCTAssertEqual(
+                scrollView.contentInset,
+                UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
+            )
+
+            fpc.move(to: .full, animated: false)
+            fpc.floatingPanel.adjustScrollContentInsetIfNeeded()
+            XCTAssertEqual(
+                scrollView.contentInset,
+                UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
+            )
+        }
+    }
+
     func test_initial_scroll_offset_reset() {
         let fpc = FloatingPanelController()
         let scrollView = UIScrollView()