Bugfix FXIOS-13606 Remove delay while clicking "Set as Default Browser"

BrowserKit/Sources/ComponentLibrary/BottomSheet/BottomSheetViewController.swift

@@ -37,7 +37,7 @@ public class BottomSheetViewController: UIViewController,
     public var themeManager: ThemeManager
     public var themeListenerCancellable: Any?
 
-    private let viewModel: BottomSheetViewModel
+    internal let viewModel: BottomSheetViewModel
     private var useDimmedBackground: Bool
     private let childViewController: BottomSheetChild
 
@@ -62,7 +62,7 @@ public class BottomSheetViewController: UIViewController,
     private lazy var sheetView: UIView = .build { _ in }
     private lazy var contentView: UIView = .build { _ in }
     private lazy var scrollContentView: UIView = .build { _ in }
-    private var contentViewBottomConstraint: NSLayoutConstraint?
+    internal var contentViewBottomConstraint: NSLayoutConstraint?
     private var viewTranslation = CGPoint(x: 0, y: 0)
     private let windowUUID: WindowUUID
     private var glassEffectView: UIVisualEffectView?

BrowserKit/Sources/ComponentLibrary/BottomSheet/OnboardingBottomSheetViewController.swift

@@ -0,0 +1,34 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/
+
+import Common
+import Foundation
+import UIKit
+
+/// A specialized bottom sheet controller for onboarding flows that uses viewWillAppear for animations
+@MainActor
+public class OnboardingBottomSheetViewController: BottomSheetViewController {
+    // MARK: - View lifecycle
+
+    override public func viewWillAppear(_ animated: Bool) {
+        super.viewWillAppear(animated)
+
+        // For onboarding flows, we animate the bottom sheet presentation earlier in the lifecycle
+        // This ensures the animation starts before the view becomes visible, creating a smoother
+        // user experience during onboarding transitions
+        contentViewBottomConstraint?.constant = 0
+        UIView.animate(withDuration: viewModel.animationTransitionDuration) {
+            self.view.backgroundColor = self.viewModel.backgroundColor
+            self.view.layoutIfNeeded()
+        }
+    }
+
+    // swiftlint:disable:next unneeded_override
+    override public func viewDidAppear(_ animated: Bool) {
+        super.viewDidAppear(animated)
+        // Override viewDidAppear without additional animation logic since we handle
+        // all presentation animations in viewWillAppear. This prevents duplicate
+        // animations that could cause visual glitches in onboarding flows.
+    }
+}

firefox-ios/Client/Frontend/Onboarding/Protocols/OnboardingService.swift

@@ -311,7 +311,7 @@ final class OnboardingService: FeatureFlaggable {
             closeButtonA11yIdentifier:
                 AccessibilityIdentifiers.Onboarding.bottomSheetCloseButton
         )
-        let bottomSheetVC = BottomSheetViewController(
+        let bottomSheetVC = OnboardingBottomSheetViewController(
             viewModel: bottomSheetViewModel,
             childViewController: instructionsVC,
             usingDimmedBackground: true,