SyntaxEditorUI

SyntaxEditorUI is a Swift package for building editable plain-text and syntax-highlighted code views on iOS and macOS. It provides SwiftUI, UIKit, and AppKit entry points with built-in language support, editor shortcuts, and common code-editing behavior.

Features

• Editable code views for SwiftUI, UIKit, and AppKit apps.
• Plain Text editing plus syntax highlighting for CSS, HTML, JavaScript, JSON, Objective-C, Swift, TOML, and XML.
• Embedded JavaScript and CSS highlighting inside HTML.
• Code-aware editing behavior for supported syntax-highlighted languages:
  • bracket and quote auto-pairing
  • smart newline indentation
  • line indent and outdent
  • comment toggling for supported languages
  • pair-aware backspace deletion
  • matching bracket highlight
• Keyboard shortcuts for common editor actions.
• iOS accessory controls for undo, redo, and keyboard dismissal.
• Programmatic control over text, language, editability, line wrapping, theme, font size, and background drawing.

Requirements

• Swift 6.3+
• iOS 18+
• Mac Catalyst 18+
• macOS 15+
• visionOS 2+

Shortcuts

• Tab: Insert spaces at the caret; indent selected lines in syntax-highlighted language modes
• Shift-Tab: Outdent in syntax-highlighted language modes
• Cmd+]: Indent in syntax-highlighted language modes
• Cmd+[ : Outdent in syntax-highlighted language modes
• Cmd+/: Toggle comment (HTML/JavaScript/CSS/Objective-C/Swift/TOML/XML)
• Ctrl+Shift+Cmd+L: Toggle line wrapping
• Cmd++: Increase font size
• Cmd+-: Decrease font size
• Ctrl+Cmd+0: Reset font size
• Cmd+Z: Undo
• Shift+Cmd+Z: Redo
• Cmd+F: Find
• Cmd+G: Find next
• Shift+Cmd+G: Find previous

Usage

SwiftUI

import SwiftUI
import SyntaxEditorUI

struct EditorView: View {
    @State private var model = SyntaxEditorModel(
        text: "const answer = 42;",
        language: .javascript
    )

    var body: some View {
        SyntaxEditor(model)
            .onChange(of: model.text) {
                print("Edited text:", model.text)
            }
    }
}

UIKit / AppKit

import SyntaxEditorUI

let model = SyntaxEditorModel(
    text: "const answer = 42;",
    language: .javascript
)

let editorView = SyntaxEditorView(model: model)
let editorViewController = SyntaxEditorViewController(model: model)

Use SyntaxLanguage.plainText when an editor should behave as strict plain text without syntax highlighting or code-aware editing transforms:

let notesModel = SyntaxEditorModel(text: "Notes", language: .plainText)

Supported languages are available through SyntaxLanguage: Plain Text, CSS, HTML, JavaScript, JSON, Objective-C, Swift, TOML, and XML. Use SyntaxLanguage(identifier:) when resolving user input or file metadata, and SyntaxLanguage.allCases when presenting every built-in language.

To move first-use highlighting setup out of the editor load path, prepare the languages your app expects to show:

Task.detached {
    await SyntaxEditorHighlighting.prepare([.swift, .html])
}

Set model.drawsBackground = false when the surrounding view should provide the editor background while syntax colors and editor decorations remain active. Use model.fontSizeDelta, increaseFontSize(), decreaseFontSize(), and resetFontSize() for Xcode-style point-size adjustments relative to the selected theme.

Use SyntaxEditorMenu when an app wants to expose editor shortcuts in an Editor menu. On iOS 26 and later, install it from the app delegate's main menu configuration:

if #available(iOS 26.0, *) {
    UIMainMenuSystem.shared.setBuildConfiguration(UIMainMenuSystem.Configuration()) { builder in
        SyntaxEditorMenu.insert(into: builder)
    }
}

On iPadOS, first-responder key commands can also appear under Help > Other Keyboard Shortcuts; install the Editor menu through the main menu builder when the commands should appear as a menu bar menu.

On macOS, insert the menu item into the app's main menu:

SyntaxEditorMenu.insert(into: NSApp.mainMenu!)

iPad Pointer Input

Apps that use SyntaxEditorView on iPadOS should enable UIApplicationSupportsIndirectInputEvents in their Info.plist. With this key enabled, mouse and trackpad click-drags are handled by UIKit text selection instead of scroll dragging, while finger drag scrolling and trackpad or mouse wheel scrolling continue to work.

Testing

swift test
xcrun simctl list devices available
DESTINATION='platform=iOS Simulator,id=<simulator-udid>'
xcodebuild test -workspace SyntaxEditorUI.xcworkspace -scheme SyntaxEditorUITests -testPlan SyntaxEditorUITests -only-testing:SyntaxEditorCorePlatformTests -only-testing:SyntaxEditorUITests -destination "$DESTINATION" -enableCodeCoverage NO -parallel-testing-enabled NO -maximum-concurrent-test-simulator-destinations 1

GitHub Actions runs swift test on macOS for package-wide coverage, then runs SyntaxEditorCorePlatformTests and SyntaxEditorUITests on the latest available iOS simulator for UIKit-specific coverage.

Mini is a lightweight manual verification app for iOS/macOS. It is not a public product and does not own package regression tests.

Performance Benchmarks

Highlighting performance benchmarks are exposed through the SwiftPM benchmark plugin:

swift package benchmark list --target HighlightBenchmark
swift package benchmark run --target HighlightBenchmark --filter 'fixture-swift-structural-edit/highlight/incremental-update' --time-units microseconds --no-progress
swift package --allow-writing-to-package-directory benchmark baseline update before --target HighlightBenchmark --filter 'fixture-swift-structural-edit/highlight/incremental-update'
swift package benchmark baseline compare before --target HighlightBenchmark --filter 'fixture-swift-structural-edit/highlight/incremental-update'
SYNTAX_EDITOR_BENCHMARK_FILE=/path/to/file.swift swift package benchmark run --target HighlightBenchmark

The benchmark suite uses bundled reference samples by default and repeats them to around 10,000 lines. Large cases repeat to around 50,000 lines. Set SYNTAX_EDITOR_BENCHMARK_FILE to benchmark a custom file, and optionally set SYNTAX_EDITOR_BENCHMARK_LANGUAGE, SYNTAX_EDITOR_BENCHMARK_REPEAT_SOURCE, SYNTAX_EDITOR_BENCHMARK_ITERATIONS, SYNTAX_EDITOR_BENCHMARK_TYPING_EDITS, SYNTAX_EDITOR_BENCHMARK_TYPING_ANCHOR, SYNTAX_EDITOR_BENCHMARK_TYPE_TEXT, SYNTAX_EDITOR_BENCHMARK_TYPE_AFTER, or SYNTAX_EDITOR_BENCHMARK_TYPE_REPEAT to adjust the run. SYNTAX_EDITOR_BENCHMARK_REPEAT_SOURCE overrides the default sample amplification.

Benchmarks are intended for local development and are not part of regular CI. Performance regression checks should run on a dedicated machine or a manually triggered workflow to avoid shared-runner noise.

Migration

v0.15.0

These notes apply when upgrading from v0.14.x or earlier to v0.15.0.

• SyntaxEditorTextEdit has been replaced by SyntaxEditorTextChange.Replacement.
• SyntaxEditorTextChange.edits has been renamed to replacements.
• SyntaxEditorTextChange.revision has been renamed to textRevision.
• SyntaxEditorModel.latestChange has been renamed to latestTextChange.
• SyntaxEditorTextChange.Kind.replacement has been renamed to wholeDocumentReplacement.
• Platform color and font aliases now live under SyntaxEditorTheme as SyntaxEditorTheme.Color and SyntaxEditorTheme.Font.
• SyntaxEditorMenu.makeEditorMenu() and SyntaxEditorMenu.makeEditorMenuItem() have been replaced by SyntaxEditorMenu.makeMenu().
• SyntaxEditorMenu.insertEditorMenu(into:) and SyntaxEditorMenu.insertEditorMenuItem(into:) have been replaced by SyntaxEditorMenu.insert(into:).
• SyntaxLanguage.named(_:) has been replaced by SyntaxLanguage.init?(identifier:).
• SyntaxLanguage.all has been removed. Use SyntaxLanguage.allCases.

v0.12.0

These notes apply when upgrading from v0.11.x or earlier to v0.12.0.

• SyntaxEditorColorTheme has been renamed to SyntaxEditorTheme.
• SyntaxEditorModel.colorTheme and the colorTheme: initializer argument have been renamed to theme and theme:.
• Custom SyntaxEditorTheme values must include a font. Themes now own editor font size; the editor no longer falls back to a package-level default point size.

v0.11.0

These notes apply when upgrading from v0.10.x or earlier to v0.11.0.

• SyntaxEditorDocument and SyntaxEditorConfiguration have been removed. Create and own a single SyntaxEditorModel for text, selection, language, editability, wrapping, theme, background drawing, and font-size state.
• SyntaxLanguage.plainText has been added. Update exhaustive switches over SyntaxLanguage to handle plain text, and use .plainText for editors that should not run syntax highlighting or code-aware editing transforms.
• textSnapshot() has been removed. Read, write, and observe model.text directly. Use model.replaceText(_:selectedRange:) when replacement and selection should be updated together.
• Replace SyntaxEditor(document:configuration:) with SyntaxEditor(model).
• Replace SyntaxEditorView(document:configuration:) and SyntaxEditorViewController(document:configuration:) with SyntaxEditorView(model:) and SyntaxEditorViewController(model:).
• SyntaxEditorDocumentChange has been renamed to SyntaxEditorTextChange. Use change.kind == .incremental or change.kind == .wholeDocumentReplacement instead of isWholeDocumentReplacement.
• UIKit and AppKit text, selectedRange, and isEditable properties remain available and now proxy to the view's model.
• On macOS, SyntaxEditorView no longer exposes the underlying editor as NSTextView. The editor surface is implemented directly with TextKit 2, matching the iOS architecture. Use SyntaxEditorView.text, SyntaxEditorView.selectedRange, SyntaxEditorView.isEditable, and SyntaxEditorView.model instead of reaching through textView.
• This is a breaking macOS API change: there is no replacement public NSTextView accessor. Code that previously customized editorView.textView should move editor state to SyntaxEditorModel or drive the editor through the public SyntaxEditorView properties above.
• SyntaxEditorViewController.textView is no longer public on macOS. Access the editor through SyntaxEditorViewController.editorView and model.

v0.10.0

These notes apply when upgrading from v0.9.x or earlier to v0.10.0.

• SyntaxEditorView.font has been removed from the public iOS API. Use SyntaxEditorModel.fontSizeDelta or the font-size command methods to adjust editor text size.

v0.8.0

These notes apply when upgrading from v0.7.x or earlier to v0.8.0.

• SyntaxEditorColorTheme.xcode has been removed. Use SyntaxEditorColorTheme.default, shorthand .default, or SyntaxEditorColorTheme.preset(_:) instead.
• SyntaxEditorColorTheme.id is now a String instead of a UUID. If your app stores or compares theme IDs, migrate those values to strings.

v0.7.0

These notes apply when upgrading from v0.6.x or earlier to v0.7.0.

• SyntaxEditorModel has been replaced by separate SyntaxEditorDocument and SyntaxEditorConfiguration objects.
• Store editor text in SyntaxEditorDocument. Read the current text with textSnapshot() and replace it with replaceText(_:selectedRange:).
• Store editor settings in SyntaxEditorConfiguration: language, isEditable, lineWrappingEnabled, and colorTheme.
• Replace SyntaxEditor(model:) with SyntaxEditor(document:configuration:). SyntaxEditor() is also available when the default document and configuration are enough.
• Replace SyntaxEditorView(model:) and SyntaxEditorViewController(model:) with SyntaxEditorView(document:configuration:) and SyntaxEditorViewController(document:configuration:).
• If your app observed SyntaxEditorModel, observe SyntaxEditorDocument for text changes and SyntaxEditorConfiguration for configuration changes. SyntaxEditorDocument exposes textRevision and latestTextChange for tracking committed text changes.
• SyntaxEditorModel and the model-based initializers have been removed without a compatibility shim.

v0.5.0

These notes apply when upgrading from v0.4.x or earlier to v0.5.0.

• Starting with v0.5.0, non-UI implementation has moved into the internal SyntaxEditorCore target. SyntaxEditorCore is not a public package product; clients should keep importing SyntaxEditorUI only.
• In v0.5.0, SyntaxEditorModel, SyntaxLanguage, and related non-UI APIs remained available from SyntaxEditorUI via module re-export. SyntaxEditorModel was removed in v0.7.0; see the v0.7.0 notes above.
• SyntaxLanguage is now a concrete enum of supported languages. Use SyntaxLanguage.javascript or shorthand .javascript instead of BuiltinSyntaxLanguages.javascript.
• BuiltinSyntaxLanguages has been removed without a compatibility shim.
• Custom SyntaxLanguage conformers are no longer supported. SyntaxLanguage.TreeSitterSupport, custom query directories, and custom highlight cache keys are no longer public API.
• HTML embedded JavaScript/CSS highlighting remains supported through SyntaxLanguage.html.
• Up to v0.4.x on iOS, SyntaxEditorView embedded a UITextView that was exposed through SyntaxEditorView.textView and SyntaxEditorViewController.textView.
• Starting with v0.5.0 on iOS, SyntaxEditorView is the single native text input and scroll view. Use SyntaxEditorView / SyntaxEditorViewController.editorView directly for text, selection, editability, wrapping, and scrolling.