dpearson2699/swift-ios-skills

Agent skills for iOS, iPadOS, Swift, SwiftUI, and modern Apple framework development.

Quality

90%

Does it follow best practices?

Impact

—

Average score across 248 eval scenarios

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Suggest reviewing before use

name:: paperkit
description:: Add drawings, shapes, and a consistent markup experience using PaperKit. Use when integrating PaperMarkupViewController for markup editing, adding shape recognition, working with PaperMarkup data models, embedding markup tools in document editors, or building annotation features that need the system-standard markup toolbar. New in iOS 26.

PaperKit

Name: dpearson2699/swift-ios-skills
Rating: 90.31 (1 reviews)
Author: dpearson2699

Beta-sensitive. PaperKit is new in iOS/iPadOS 26, macOS 26, and visionOS 26. API surface may change. Verify details against current Apple documentation before shipping.

PaperKit provides a unified markup experience — the same framework powering markup in Notes, Screenshots, QuickLook, and Journal. It combines PencilKit drawing with structured markup elements (shapes, text boxes, images, lines) in a single canvas managed by PaperMarkupViewController. Requires Swift 6.3 and the iOS 26+ SDK.

Setup
PaperMarkupViewController
PaperMarkup Data Model
Insertion Controllers
FeatureSet Configuration
Integration with PencilKit
SwiftUI Integration
Common Mistakes
Review Checklist
References

Setup

PaperKit requires no entitlements or special Info.plist entries.

import PaperKit

Platform availability: iOS 26.0+, iPadOS 26.0+, Mac Catalyst 26.0+, macOS 26.0+, visionOS 26.0+.

Three core components:

Component	Role
`PaperMarkupViewController`	Interactive canvas for creating and displaying markup and drawing
`PaperMarkup`	Data model for serializing all markup elements and PencilKit drawing
`MarkupEditViewController` / `MarkupToolbarViewController`	Insertion UI for adding markup elements

PaperMarkupViewController

The primary view controller for interactive markup. Provides a scrollable canvas for freeform PencilKit drawing and structured markup elements. Conforms to Observable and PKToolPickerObserver.

Basic UIKit Setup

import PaperKit
import PencilKit
import UIKit

class MarkupViewController: UIViewController, PaperMarkupViewController.Delegate {
    var paperVC: PaperMarkupViewController!
    var toolPicker: PKToolPicker!

    override func viewDidLoad() {
        super.viewDidLoad()

        let pageBounds = CGRect(origin: .zero, size: CGSize(width: 612, height: 792))
        let markup = PaperMarkup(bounds: pageBounds)
        let features = FeatureSet.latest

        paperVC = PaperMarkupViewController(
            markup: markup,
            supportedFeatureSet: features
        )
        paperVC.delegate = self

        addChild(paperVC)
        paperVC.view.frame = view.bounds
        paperVC.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.addSubview(paperVC.view)
        paperVC.didMove(toParent: self)

        toolPicker = PKToolPicker()
        toolPicker.addObserver(paperVC)
        paperVC.pencilKitResponderState.activeToolPicker = toolPicker
        paperVC.pencilKitResponderState.toolPickerVisibility = .visible
    }

    func paperMarkupViewControllerDidChangeMarkup(
        _ controller: PaperMarkupViewController
    ) {
        guard let markup = controller.markup else { return }
        Task { try await save(markup) }
    }
}

Key Properties

Property	Type	Description
`markup`	`PaperMarkup?`	The current data model
`selectedMarkup`	`PaperMarkup`	Currently selected content
`isEditable`	`Bool`	Whether the canvas accepts input
`isRulerActive`	`Bool`	Whether the ruler overlay is shown
`drawingTool`	`any PKTool`	Active PencilKit drawing tool
`contentView`	`UIView?` / `NSView?`	Background view rendered beneath markup
`zoomRange`	`ClosedRange<CGFloat>`	Min/max zoom scale
`supportedFeatureSet`	`FeatureSet`	Enabled PaperKit features

Touch Modes

PaperMarkupViewController.TouchMode has two cases: .drawing and .selection.

paperVC.directTouchMode = .drawing    // Finger draws
paperVC.directTouchMode = .selection  // Finger selects elements
paperVC.directTouchAutomaticallyDraws = true  // System decides based on Pencil state

Content Background

Set any view beneath the markup layer for templates, document pages, or images being annotated. Keep the PaperMarkup(bounds:) coordinate space aligned to the background content, such as a PDF page or rendered image size, so saved annotations restore in the right place:

let pageBounds = CGRect(origin: .zero, size: pageImage.size)
let imageView = UIImageView(image: pageImage)
imageView.frame = pageBounds

let markup = PaperMarkup(bounds: pageBounds)
paperVC = PaperMarkupViewController(markup: markup, supportedFeatureSet: features)
paperVC.contentView = imageView

Delegate Callbacks

Method	Called when
`paperMarkupViewControllerDidChangeMarkup(_:)`	Markup content changes
`paperMarkupViewControllerDidBeginDrawing(_:)`	User starts drawing
`paperMarkupViewControllerDidChangeSelection(_:)`	Selection changes
`paperMarkupViewControllerDidChangeContentVisibleFrame(_:)`	Visible frame changes

PaperMarkup Data Model

PaperMarkup is a Sendable struct that stores all markup elements and PencilKit drawing data.

Creating and Persisting

// New empty model. Bounds define the saved document coordinate space.
let markup = PaperMarkup(bounds: CGRect(x: 0, y: 0, width: 612, height: 792))

// Load from saved data
let markup = try PaperMarkup(dataRepresentation: savedData)

// Save — dataRepresentation() is async throws
func save(_ markup: PaperMarkup) async throws {
    let data = try await markup.dataRepresentation()
    try data.write(to: fileURL)
}

Inserting Content Programmatically

// Text box
markup.insertNewTextbox(
    attributedText: AttributedString("Annotation"),
    frame: CGRect(x: 50, y: 100, width: 200, height: 40),
    rotation: 0
)

// Image
markup.insertNewImage(cgImage, frame: CGRect(x: 50, y: 200, width: 300, height: 200), rotation: 0)

// Shape
let shapeConfig = ShapeConfiguration(
    type: .rectangle,
    fillColor: UIColor.systemBlue.withAlphaComponent(0.2).cgColor,
    strokeColor: UIColor.systemBlue.cgColor,
    lineWidth: 2
)
markup.insertNewShape(configuration: shapeConfig, frame: CGRect(x: 50, y: 420, width: 200, height: 100), rotation: 0)

// Line with arrow end marker
let lineConfig = ShapeConfiguration(type: .line, fillColor: nil, strokeColor: UIColor.red.cgColor, lineWidth: 3)
markup.insertNewLine(
    configuration: lineConfig,
    from: CGPoint(x: 50, y: 550), to: CGPoint(x: 250, y: 550),
    startMarker: false, endMarker: true
)

Shape types: .rectangle, .roundedRectangle, .ellipse, .line, .arrowShape, .star, .chatBubble, .regularPolygon.

Other Operations

markup.append(contentsOf: otherMarkup)       // Merge another PaperMarkup
markup.append(contentsOf: pkDrawing)          // Merge a PKDrawing
markup.transformContent(CGAffineTransform(...)) // Apply affine transform
markup.removeContentUnsupported(by: featureSet) // Strip unsupported elements

Property	Description
`bounds`	Coordinate space of the markup
`contentsRenderFrame`	Tight bounding box of all content
`featureSet`	Features used by this data model's content
`indexableContent`	Extractable text for search indexing

Use suggestedFrameForInserting(contentInFrame:) on the view controller to get a frame that avoids overlapping existing content.

Insertion Controllers

MarkupEditViewController (iOS, iPadOS, Mac Catalyst, visionOS)

Presents a popover menu for inserting shapes, text boxes, lines, and other elements.

func showInsertionMenu(from barButtonItem: UIBarButtonItem) {
    let editVC = MarkupEditViewController(
        supportedFeatureSet: paperVC.supportedFeatureSet,
        additionalActions: []
    )
    editVC.delegate = paperVC  // PaperMarkupViewController conforms to the delegate
    editVC.modalPresentationStyle = .popover
    editVC.popoverPresentationController?.barButtonItem = barButtonItem
    present(editVC, animated: true)
}

MarkupToolbarViewController (macOS, Mac Catalyst)

Provides a toolbar with drawing tools and insertion buttons. Use it for native macOS and for Mac Catalyst toolbar-style UI; Catalyst apps that want a UIKit popover can use MarkupEditViewController.

let toolbar = MarkupToolbarViewController(supportedFeatureSet: paperVC.supportedFeatureSet)
toolbar.delegate = paperVC
addChild(toolbar)
toolbar.view.frame = toolbarContainerView.bounds
toolbarContainerView.addSubview(toolbar.view)
toolbar.didMove(toParent: self)

Both controllers must use the same FeatureSet as the PaperMarkupViewController.

FeatureSet Configuration

FeatureSet controls which markup capabilities are available.

Preset	Description
`.latest`	All current features — recommended starting point
`.version1`	Features from version 1
`.empty`	No features enabled

Customizing

var features = FeatureSet.latest
features.remove(.stickers)
features.remove(.images)

// Or build up from empty
var features = FeatureSet.empty
features.insert(.drawing)
features.insert(.text)
features.insert(.shapeStrokes)

Available Features

Feature	Description
`.drawing`	Freeform PencilKit drawing
`.text`	Text box insertion
`.images`	Image insertion
`.stickers`	Sticker insertion
`.links`	Link annotations
`.loupes`	Loupe/magnifier elements
`.shapeStrokes`	Shape outlines
`.shapeFills`	Shape fills
`.shapeOpacity`	Shape opacity control

HDR Support

Set colorMaximumLinearExposure above 1.0 on both the FeatureSet and PKToolPicker:

var features = FeatureSet.latest
features.colorMaximumLinearExposure = 4.0
toolPicker.colorMaximumLinearExposure = features.colorMaximumLinearExposure

Use view.window?.windowScene?.screen.potentialEDRHeadroom to match the device screen's capability. Use 1.0 for SDR-only.

Shapes, Inks, and Line Markers

features.shapes = [.rectangle, .ellipse, .arrowShape, .line]
features.inks = [.pen, .pencil, .marker]
features.lineMarkerPositions = .all  // .single, .double, .plain, or .all

Integration with PencilKit

PaperKit accepts PKTool for drawing and can append PKDrawing content.

PaperKit is not a drop-in replacement for a low-level PKCanvasView when the app depends on custom brush behavior, raw PKDrawing / PKStroke analytics, or custom lasso-centric editing. Keep those workflows owned by PencilKit, and add PaperKit beside them for structured review markup such as callouts, arrows, text boxes, labels, image stamps, and system-standard insertion UI. Migrate or duplicate existing drawings into a PaperKit annotation layer with PaperMarkup.append(contentsOf: PKDrawing) only when the low-level editing path no longer needs to own that content.

import PencilKit

// Set drawing tool
paperVC.drawingTool = PKInkingTool(.pen, color: .black, width: 3)

// Merge existing PKDrawing into markup
markup.append(contentsOf: existingPKDrawing)

Tool Picker Setup

let toolPicker = PKToolPicker()
toolPicker.addObserver(paperVC)
paperVC.pencilKitResponderState.activeToolPicker = toolPicker
paperVC.pencilKitResponderState.toolPickerVisibility = .visible

Setting toolPickerVisibility to .hidden keeps the picker functional (responds to Pencil gestures) but not visible, enabling the mini tool picker experience.

Content Version Compatibility

FeatureSet.ContentVersion maps to PKContentVersion:

let pkVersion = features.contentVersion.pencilKitContentVersion

SwiftUI Integration

Wrap PaperMarkupViewController in UIViewControllerRepresentable:

struct MarkupView: UIViewControllerRepresentable {
    @Binding var markup: PaperMarkup
    let features: FeatureSet

    func makeUIViewController(context: Context) -> PaperMarkupViewController {
        let vc = PaperMarkupViewController(markup: markup, supportedFeatureSet: features)
        vc.delegate = context.coordinator
        let toolPicker = PKToolPicker()
        toolPicker.addObserver(vc)
        vc.pencilKitResponderState.activeToolPicker = toolPicker
        vc.pencilKitResponderState.toolPickerVisibility = .visible
        context.coordinator.toolPicker = toolPicker
        return vc
    }

    func updateUIViewController(_ vc: PaperMarkupViewController, context: Context) {
        if vc.markup != markup { vc.markup = markup }
    }

    func makeCoordinator() -> Coordinator { Coordinator(parent: self) }

    class Coordinator: NSObject, PaperMarkupViewController.Delegate {
        let parent: MarkupView
        var toolPicker: PKToolPicker?
        init(parent: MarkupView) { self.parent = parent }

        func paperMarkupViewControllerDidChangeMarkup(
            _ controller: PaperMarkupViewController
        ) {
            if let markup = controller.markup { parent.markup = markup }
        }
    }
}

Initialize the bound PaperMarkup from the document or page size before creating the SwiftUI bridge:

struct DocumentMarkupScreen: View {
    let pageSize: CGSize
    @State private var markup: PaperMarkup
    private let features = FeatureSet.latest

    init(pageSize: CGSize) {
        self.pageSize = pageSize
        _markup = State(
            initialValue: PaperMarkup(
                bounds: CGRect(origin: .zero, size: pageSize)
            )
        )
    }

    var body: some View {
        MarkupView(markup: $markup, features: features)
    }
}

Common Mistakes

Mismatched FeatureSets

// DON'T
let paperVC = PaperMarkupViewController(markup: m, supportedFeatureSet: .latest)
let editVC = MarkupEditViewController(supportedFeatureSet: .version1, additionalActions: [])

// DO — use the same FeatureSet for both
let features = FeatureSet.latest
let paperVC = PaperMarkupViewController(markup: m, supportedFeatureSet: features)
let editVC = MarkupEditViewController(supportedFeatureSet: features, additionalActions: [])

Ignoring Content Version on Load

// DON'T
let markup = try PaperMarkup(dataRepresentation: data)
paperVC.markup = markup

// DO — check version compatibility
let markup = try PaperMarkup(dataRepresentation: data)
if markup.featureSet.isSubset(of: paperVC.supportedFeatureSet) {
    paperVC.markup = markup
} else {
    showVersionMismatchAlert()
}

Blocking Main Thread with Serialization

// DON'T — dataRepresentation() is async, don't try to work around it

// DO — save from an async context
func paperMarkupViewControllerDidChangeMarkup(_ controller: PaperMarkupViewController) {
    guard let markup = controller.markup else { return }
    Task {
        let data = try await markup.dataRepresentation()
        try data.write(to: fileURL)
    }
}

Forgetting to Retain the Tool Picker

// DON'T — local variable gets deallocated
func viewDidLoad() {
    let toolPicker = PKToolPicker()
    toolPicker.addObserver(paperVC)
}

// DO — store as instance property
var toolPicker: PKToolPicker!

Wrong Insertion Controller for Platform

// DON'T — treat MarkupEditViewController as unavailable on Mac Catalyst

// DO — use the right UI for the presentation style
#if os(macOS)
let toolbar = MarkupToolbarViewController(supportedFeatureSet: features)
#elseif targetEnvironment(macCatalyst)
// Catalyst supports both: toolbar-style UI or UIKit popover insertion.
let toolbar = MarkupToolbarViewController(supportedFeatureSet: features)
let editVC = MarkupEditViewController(supportedFeatureSet: features, additionalActions: [])
#else
let editVC = MarkupEditViewController(supportedFeatureSet: features, additionalActions: [])
#endif

Review Checklist

References

PaperKit documentation
Integrating PaperKit into your app
Meet PaperKit — WWDC25
The pencilkit skill covers PencilKit drawing, tool pickers, and PKDrawing serialization
references/paperkit-patterns.md — data persistence, rendering, multi-platform setup, custom feature sets

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README.md

tile.json

dpearson2699/swift-ios-skills

SKILL.mdskills/paperkit/

PaperKit

Contents

Setup

PaperMarkupViewController

Basic UIKit Setup

Key Properties

Touch Modes

Content Background

Delegate Callbacks

PaperMarkup Data Model

Creating and Persisting

Inserting Content Programmatically

Other Operations

Insertion Controllers

MarkupEditViewController (iOS, iPadOS, Mac Catalyst, visionOS)

MarkupToolbarViewController (macOS, Mac Catalyst)

FeatureSet Configuration

Customizing

Available Features

HDR Support

Shapes, Inks, and Line Markers

Integration with PencilKit

Tool Picker Setup

Content Version Compatibility

SwiftUI Integration

Common Mistakes

Mismatched FeatureSets

Ignoring Content Version on Load

Blocking Main Thread with Serialization

Forgetting to Retain the Tool Picker

Wrong Insertion Controller for Platform

Review Checklist

References

dpearson2699/swift-ios-skills

SKILL.md.css-3qkkll{font-size:var(--chakra-font-sizes-sm);font-weight:var(--chakra-font-weights-normal);color:var(--chakra-colors-gray-300);}skills/paperkit/

PaperKit

Contents

Setup

PaperMarkupViewController

Basic UIKit Setup

Key Properties

Touch Modes

Content Background

Delegate Callbacks

PaperMarkup Data Model

Creating and Persisting

Inserting Content Programmatically

Other Operations

Insertion Controllers

MarkupEditViewController (iOS, iPadOS, Mac Catalyst, visionOS)

MarkupToolbarViewController (macOS, Mac Catalyst)

FeatureSet Configuration

Customizing

Available Features

HDR Support

Shapes, Inks, and Line Markers

Integration with PencilKit

Tool Picker Setup

Content Version Compatibility

SwiftUI Integration

Common Mistakes

Mismatched FeatureSets

Ignoring Content Version on Load

Blocking Main Thread with Serialization

Forgetting to Retain the Tool Picker

Wrong Insertion Controller for Platform

Review Checklist

References

SKILL.mdskills/paperkit/