Customize PDF view margins using Swift for iOS

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//
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//  Copyright © 2016-2025 PSPDFKit GmbH. All rights reserved.
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//
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//  The Nutrient sample applications are licensed with a modified BSD license.
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//  Please see License for details. This notice may not be removed from this file.
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//
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import PSPDFKit
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import PSPDFKitUI
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class DynamicMarginsExample: Example {
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    override init() {
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        super.init()
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        title = "Margin Customization Example"
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        contentDescription = "Shows how adjust the content for your custom user interface elements."
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        category = .controllerCustomization
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController? {
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        let document = AssetLoader.document(for: .welcome)
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        let pdfController = CustomUserInterfaceController(document: document) {
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            $0.pageTransition = .curl
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            $0.userInterfaceViewMode = .always
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            $0.thumbnailBarMode = .none
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        }
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        return pdfController
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    }
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    // MARK: - View controller
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    class CustomUserInterfaceController: PDFViewController {
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        override func viewDidLoad() {
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            super.viewDidLoad()
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            setUpBottomBar()
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        }
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        // MARK: Bottom bar
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        let bottomBar = CustomBottomBar()
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        private func setUpBottomBar() {
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            bottomBar.toggleButton.addTarget(self, action: #selector(togglePressed), for: .touchUpInside)
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            bottomBar.translatesAutoresizingMaskIntoConstraints = false
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            userInterfaceView.addSubview(bottomBar)
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            let views = ["bottomBar": bottomBar]
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            NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "|-0-[bottomBar]-0-|", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views))
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            NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "V:[bottomBar]-0-|", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views))
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            updateCongigurationForBottomBar()
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        }
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        @objc private func togglePressed() {
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            bottomBar.expanded = !bottomBar.expanded
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            updateCongigurationForBottomBar()
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        }
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        private func updateCongigurationForBottomBar() {
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            let bottomBarInset = bottomBar.intrinsicContentSize.height
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            // Note changing the margin requires updateConfigurationWithBuilder (a reload).
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            updateConfiguration {
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                $0.additionalScrollViewFrameInsets = UIEdgeInsets(top: 0, left: 0, bottom: bottomBarInset, right: 0)
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            }
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            // Lets also move the page label above the bottom bar.
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            userInterfaceView.pageLabelInsets = UIEdgeInsets(top: 0, left: 5, bottom: 10 + bottomBarInset, right: 5)
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        }
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    }
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    // MARK: - User Interface view
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    class CustomBottomBar: UIView {
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        override init(frame: CGRect) {
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            super.init(frame: frame)
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            setUpViews()
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        }
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        required init?(coder aDecoder: NSCoder) {
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            super.init(coder: aDecoder)
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            setUpViews()
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        }
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        private func setUpViews() {
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            backgroundColor = UIColor.catalogAccent.withAlphaComponent(0.7)
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            toggleButton.setTitle("Expand / Collapse", for: UIControl.State())
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            toggleButton.translatesAutoresizingMaskIntoConstraints = false
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            addSubview(toggleButton)
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            NSLayoutConstraint(item: toggleButton, attribute: .centerX, relatedBy: .equal, toItem: self, attribute: .centerX, multiplier: 1, constant: 0).isActive = true
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            NSLayoutConstraint(item: toggleButton, attribute: .centerY, relatedBy: .equal, toItem: self, attribute: .centerY, multiplier: 1, constant: 0).isActive = true
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        }
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        // MARK: State
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        let toggleButton = UIButton(type: .custom)
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        var expanded = false {
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            didSet {
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                invalidateIntrinsicContentSize()
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            }
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        }
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        // MARK: Layout
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        override var intrinsicContentSize: CGSize {
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            return CGSize(width: UIView.noIntrinsicMetric, height: expanded ? 44 * 3 : 44)
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        }
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    }
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}