[simonbs]

Adds misspelling underlines and tap-to-correct suggestions using public UITextChecker APIs. Setting spellCheckingType = .yes enables checking independently of autocorrection; the private UIKit replacement-object workaround is removed.

On iOS 16 and later, tapping a misspelled word opens a compact system menu containing corrections. Tapping another word, blank space, or scrolling dismisses it. Selecting text still offers corrections in the regular edit menu. Earlier iOS versions use the regular edit-menu fallback.

Ignore Spelling, Learn Spelling, and Unlearn Spelling are hidden by default. Applications can independently expose them in spelling and regular edit menus:

textView.showIgnoreSpellingAction = true
textView.showLearnSpellingAction = true
textView.showUnlearnSpellingAction = true

These settings control menu visibility; public dictionary APIs remain available. Changes invalidate existing spelling actions. Ignored words belong to one editor's document session: edits, undo, language changes, and checking toggles preserve them; assigning text, calling setState, or explicitly resetting starts a new session. Learned words use Apple's shared dictionary. When enabled, selecting a learned word offers Unlearn Spelling even after its underline disappears. Dictionary actions preserve text, selection, and text undo history.

Checks are debounced, bounded, and scoped to visible text, including horizontally scrolled long lines. A dictionary language and delegate policy let applications exclude code or other ranges. Composing text is excluded and stale actions are rejected. Spelling pauses during Writing Tools sessions, and corrections use guarded system replacement with independent undo. Includes current main's Writing Tools improvements from #455, with exclusions and active-session edits preserved. Grammar integration and partial-word completion remain separate.

The example app includes a persistent Check Spelling setting, off by default.

Validation

• 76 focused spelling and Writing Tools framework tests passed after merging current main on iOS 26.5 / Xcode 27.2. Coverage includes independent menu settings, dictionary APIs while actions are hidden, tap geometry and unavailable interaction states, ignore isolation/session reset, shared learning/unlearning, stale actions, delegate reentrancy, Unicode boundaries, bounded checks, rendering geometry, and Writing Tools undo coexistence. The merge regression also verifies that a range excluded from Writing Tools can still accept a spelling correction under its independent policy.
• Three simulator UI workflows passed across the initial run and affected-case rerun: single-tap correction/dismissal/reopening/undo/disabling, ignore/reload, and learn/reload/unlearn. Tests assert default-hidden actions, unchanged document text for dictionary operations, and dictionary state with cleanup. The correction test passed after fixing a test tap that hit a suggestion and replacing a stale installed test runner.
• Strict SwiftLint on changed Swift files and git diff --check passed. Existing language-package lint and XCTest deployment-target warnings remain.
• Earlier implementation validation: 231 framework tests, example app build, and setting on/off/persistence checks passed. Those broader checks were not rerun for this update.

Launch the UI test Host and tap Spelling for the default correction menu or Dictionary for explicitly enabled dictionary actions. Run HostUITests/SpellCheckingTests for all three workflows.

The iOS 14/15 fallback has not been runtime-tested here. Actual Apple Intelligence generation was not exercised.

Simulator proof

Unmodified screenshots from passing UI tests. Captures support visual review; behavioral assertions are in the tests.

Single-tap suggestions, default settings	Correction applied

Opt-in Ignore / Learn	Opt-in Unlearn

Additional captures: undo, checking disabled, ignored word, and checking restored after Unlearn.

Example app setting from the earlier verified persistence check:

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