Customize PDF form appearance in Swift for iOS

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//
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//  Copyright © 2020-2026 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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/// This example shows how to customize the appearance of forms. We also add a
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/// temporary label over text and signature fields which will disappear when
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/// we type anything in the fields.
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class CustomizingFormAppearanceExample: Example {
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    override init() {
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        super.init()
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        title = "Customizing the Appearance of Forms"
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        contentDescription = "Also adds labels over empty text and signature fields."
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        category = .forms
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        priority = 10
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
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        let document = AssetLoader.writableDocument(for: "Form.pdf", overrideIfExists: true)
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        /// These options clear out the default form field color so that
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        /// we can customize it dynamically later in the example.
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        let options = document.renderOptions(forType: .page)
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        options.drawSignHereOverlay = false
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        options.interactiveFormFillColor = UIColor.clear
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        document.setRenderOptions(options, type: .page)
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        let controller = PDFViewController(document: document) {
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            $0.pageTransition = .scrollPerSpread
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            $0.overrideClass(PDFPageView.self, with: CustomFormPDFPageView.self)
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        }
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        controller.delegate = self
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        styleTextFieldFormElements(in: document)
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        return controller
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    }
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    private func styleTextFieldFormElements(in document: Document) {
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        let annotations = document.annotationsForPage(at: 0, type: .widget)
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        for annotation in annotations {
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            if let formElement = annotation as? TextFieldFormElement {
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                formElement.highlightColor = UIColor.clear
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                formElement.fillColor = UIColor(red: 221.0 / 255.0, green: 240.0 / 255.0, blue: 236.0 / 255.0, alpha: 1)
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                formElement.borderColor = UIColor.clear
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                formElement.borderStyle = .none
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                formElement.borderEffectIntensity = 0.0
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            }
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        }
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    }
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}
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extension CustomizingFormAppearanceExample: PDFViewControllerDelegate {
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    func pdfViewController(_ pdfController: PDFViewController, willBeginDisplaying pageView: PDFPageView, forPageAt pageIndex: Int) {
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        if let pageView = pageView as? CustomFormPDFPageView {
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            pageView.addLabels()
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        }
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    }
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}
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private class CustomFormPDFPageView: PDFPageView {
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    /// Dictionary which keeps a mapping between the form element and its label.
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    /// Used to identify which label to remove when selecting a form field.
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    var labelList = [String: UILabel]()
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    override var frame: CGRect {
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        didSet {
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            // Re-add labels when page view frame changes
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            labelList.values.forEach { $0.removeFromSuperview() }
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            labelList.removeAll()
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            addLabels()
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        }
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    }
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    /// `prepareForReuse` automatically removes all unknown internal subviews.
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    /// We need to clear out our mapping dictionary as well.
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    override func prepareForReuse() {
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        labelList.removeAll()
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        super.prepareForReuse()
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    }
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    /// Add labels over all the text and signature fields.
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    func addLabels() {
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        guard let document = presentationContext?.document else { return }
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        let annotations = document.annotationsForPage(at: pageIndex, type: .widget)
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        for annotation in annotations {
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            if let formElement = annotation as? FormElement {
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                addLabelOnFormElement(formElement: formElement)
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            }
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        }
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    }
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    /// Add the label on a given form element. Only add a label if the form field is empty.
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    func addLabelOnFormElement(formElement: FormElement) {
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        if !(formElement.isKind(of: TextFieldFormElement.self) || formElement.isKind(of: SignatureFormElement.self)) { return }
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        let label = labelList[formElement.uuid] ?? UILabel()
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        if let textFieldFormElement = formElement as? TextFieldFormElement {
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            if textFieldFormElement.contents != nil && textFieldFormElement.contents != "" { return }
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            label.text = textFieldFormElement.textFormField?.name ?? "Text Field"
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        }
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        if let signatureFormElement = formElement as? SignatureFormElement {
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            if signatureFormElement.isSigned || signatureFormElement.overlappingSignatureAnnotation != nil { return }
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            label.text = "Signature Field"
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        }
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        label.frame = convert(formElement.boundingBox, from: pdfCoordinateSpace)
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        label.textAlignment = .center
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        label.textColor = UIColor(red: 84.0 / 255.0, green: 178.0 / 255.0, blue: 159.0 / 255.0, alpha: 1)
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        label.backgroundColor = UIColor(red: 221.0 / 255.0, green: 240.0 / 255.0, blue: 236.0 / 255.0, alpha: 1)
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        annotationContainerView.addSubview(label)
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        labelList[formElement.uuid] = label
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    }
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    override func didSelect(_ annotations: [Annotation]) {
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        super.didSelect(annotations)
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        for annotation in annotations {
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            if let label = labelList[annotation.uuid] {
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                labelList[annotation.uuid] = nil
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                label.removeFromSuperview()
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            }
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            if let textFieldFormElement = annotation as? TextFieldFormElement {
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                textFieldFormElement.borderColor = UIColor(red: 84.0 / 255.0, green: 178.0 / 255.0, blue: 159.0 / 255.0, alpha: 1)
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                textFieldFormElement.borderStyle = .solid
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                textFieldFormElement.borderEffectIntensity = 1.0
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            }
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        }
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    }
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    override func didDeselect(_ annotations: [Annotation]) {
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        super.didDeselect(annotations)
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        for annotation in annotations {
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            if let textFieldFormElement = annotation as? TextFieldFormElement {
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                textFieldFormElement.borderColor = UIColor.clear
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                textFieldFormElement.borderStyle = .none
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                textFieldFormElement.borderEffectIntensity = 0.0
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            }
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            if let formElement = annotation as? FormElement {
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                addLabelOnFormElement(formElement: formElement)
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            }
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            if let inkAnnotation = annotation as? InkAnnotation {
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                if inkAnnotation.isSignature { addLabels() }
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            }
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        }
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    }
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}