Rotate PDF pages easily with Swift

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//
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//  Copyright © 2018-2025 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 RotatePageTemporarilyExample: Example {
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    override init() {
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        super.init()
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        title = "Rotate pages temporarily"
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        contentDescription = "Adds a button to rotate pages temporarily in 90 degree steps without writing changes to the PDF."
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        category = .viewCustomization
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
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        let document = AssetLoader.document(for: AssetName.welcome)
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        let controller = RotatePagePDFViewController(document: document) {
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            $0.pageMode = .single
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        }
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        return controller
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    }
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    // MARK: Controller
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    class RotatePagePDFViewController: PDFViewController {
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        // MARK: Lifecycle
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        override func commonInit(with document: Document?, configuration: PDFConfiguration) {
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            super.commonInit(with: document, configuration: configuration)
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            let rotatePageButton = UIBarButtonItem(title: "Rotate Page", style: .plain, target: self, action: #selector(rotatePage))
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            navigationItem.setRightBarButtonItems([thumbnailsButtonItem, searchButtonItem, rotatePageButton], animated: false)
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        }
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        // MARK: - Actions
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        @objc func rotatePage() {
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            guard let document = self.document else {
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                return
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            }
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            if !document.isValid {
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                return
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            }
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            let currentPageIndex = self.pageIndex
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            let currentRotation = document.pageInfoForPage(at: currentPageIndex)!.rotationOffset
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            let documentProvider = document.documentProviderForPage(at: currentPageIndex)
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            // Increment the rotation by 90 degrees. The supported rotation values are 0, 90, 180 or 270.
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            let updatedRotation = Rotation(rawValue: (currentRotation.rawValue + 90) % 360)!
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            // Rotates the current page.
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            documentProvider?.setRotationOffset(updatedRotation, forPageAt: currentPageIndex)
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            // Clear the cache for the rotated page, to trigger a re-render.
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            SDK.shared.cache.invalidateImages(from: document, pageIndex: currentPageIndex)
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            // Reloading the data is required because the document is currently displayed in a `PDFViewController`.
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            reloadData()
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        }
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    }
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}