Building a Genmoji-Ready Input System in SwiftUI

Exploring how to support Genmoji, rich text, and expressive input on iOS using SwiftUI + UIKit bridging.

Why This Matters

With the introduction of Genmoji in iOS 18, user expression is no longer limited to Unicode emoji. Instead, users can generate custom, image-based emoji directly from text prompts.

But here’s the catch:

Genmoji is not plain text — it’s a rich text glyph.

If your app only stores String, you’ll lose Genmoji data completely.

So the real challenge is:

• Supporting Genmoji input
• Preserving it through copy/paste
• Persisting it via serialization
• Restoring it without losing fidelity

This blog walks through building a minimal SwiftUI app that does exactly that.

Key Concept: Genmoji ≠ Emoji

Traditional emoji:

"😊" // Unicode character

Genmoji:

• Stored as image glyphs
• Embedded in NSAttributedString
• Backed by NSAdaptiveImageGlyph

This means:

• You must use rich text
• String is not enough

Architecture Overview

We’ll build a simple app with:

GenmojiNotes
├── ContentView
├── GenmojiTextEditor (UITextView bridge)
├── GenmojiTextPreview
├── GenmojiViewModel
└── RichTextStore (serialize/deserialize)

Step 1: Bridging UITextView into SwiftUI

SwiftUI’s TextEditor does not support Genmoji.

We must use UITextView.

struct GenmojiTextEditor: UIViewRepresentable {
    @Binding var attributedText: NSAttributedString

    func makeCoordinator() -> Coordinator {
        Coordinator(attributedText: $attributedText)
    }

    func makeUIView(context: Context) -> UITextView {
        let textView = UITextView()

        textView.delegate = context.coordinator
        textView.isEditable = true
        textView.allowsEditingTextAttributes = true

        if #available(iOS 18.0, *) {
            textView.supportsAdaptiveImageGlyph = true
        }

        return textView
    }

    func updateUIView(_ uiView: UITextView, context: Context) {
        if uiView.attributedText != attributedText {
            uiView.attributedText = attributedText
        }
    }

    final class Coordinator: NSObject, UITextViewDelegate {
        @Binding var attributedText: NSAttributedString

        init(attributedText: Binding<NSAttributedString>) {
            self._attributedText = attributedText
        }

        func textViewDidChange(_ textView: UITextView) {
            attributedText = textView.attributedText ?? NSAttributedString()
        }
    }
}

Important Flags

Property	Why it matters
supportsAdaptiveImageGlyph	Enables Genmoji input
allowsEditingTextAttributes	Enables copy/paste + rich editing

Step 2: Persisting Rich Text (RTFD)

To preserve Genmoji, we must serialize the attributed string.

func serialize(text: NSAttributedString) throws -> Data {
    try text.data(
        from: NSRange(location: 0, length: text.length),
        documentAttributes: [.documentType: .rtfd]
    )
}

Why RTFD?

Because it:

• Stores images + metadata
• Preserves Genmoji glyphs
• Is supported by UIKit

Step 3: Restoring Content

func deserialize(data: Data) throws -> NSAttributedString {
    try NSAttributedString(
        data: data,
        options: [.documentType: .rtfd],
        documentAttributes: nil
    )
}

Step 4: ViewModel

Keep logic out of views.

@MainActor
final class GenmojiViewModel: ObservableObject {
    @Published var inputText: NSAttributedString = NSAttributedString()
    @Published var previewText: NSAttributedString = NSAttributedString()

    private var savedData: Data?

    func save() {
        savedData = try? serialize(text: inputText)
    }

    func restore() {
        if let data = savedData {
            inputText = try? deserialize(data: data) ?? NSAttributedString()
        }
    }
}

Step 5: Preview UI

Display attributed text with another UITextView:

struct GenmojiTextPreview: UIViewRepresentable {
    let attributedText: NSAttributedString

    func makeUIView(context: Context) -> UITextView {
        let view = UITextView()
        view.isEditable = false
        return view
    }

    func updateUIView(_ uiView: UITextView, context: Context) {
        uiView.attributedText = attributedText
    }
}

Final Thoughts

Genmoji isn’t just a new feature — it represents a shift:

From text-based communication → to expressive, adaptive visual language

As iOS developers, this means:

• Thinking beyond strings
• Designing for rich content
• Treating text as a rendering system, not just data

1. Store text as NSAttributedString
2. Serialize with RTFD
3. Restore via NSAttributedString(data:)

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If you’re building for modern iOS, this is no longer optional — it’s the future of user expression.