Implementing some of position(from:toBoundary:inDirection:)

Sources/Ligature/Platform.swift

@@ -13,6 +13,21 @@ final class UTF16TextPosition: TextPosition {
 	init(value: Int) {
 		self.value = value
 	}
+
+	func offsetPosition(by amount: Int, maximum: Int) -> UTF16TextPosition? {
+		let new = value + amount
+		if new < 0 || new > maximum {
+			return nil
+		}
+
+		return UTF16TextPosition(value: new)
+	}
+}
+
+extension UTF16TextPosition {
+	public override var debugDescription: String {
+		String(value)
+	}
 }
 
 @MainActor
@@ -35,6 +50,14 @@ open class TextRange: NSObject {
 	}
 }
 
+extension TextRange {
+	open override var debugDescription: String {
+		MainActor.assumeIsolated {
+			"{\(start.debugDescription), \(end.debugDescription)}"
+		}
+	}
+}
+
 /// Matches the implementation of `UITextGranularity`.
 public enum TextGranularity : Int, Sendable, Hashable, Codable {
 	case character = 0
@@ -113,7 +136,7 @@ extension NSTextView {
 	}
 
 	public func textRange(from fromPosition: TextPosition, to toPosition: TextPosition) -> TextRange? {
-		nil
+		TextRange(start: fromPosition, end: toPosition)
 	}
 
 	public func position(from position: TextPosition, offset: Int) -> TextPosition? {

Sources/Ligature/TextInputStringTokenizer.swift

@@ -2,21 +2,6 @@ import Foundation
 #if os(macOS)
 import AppKit
 
-extension NSTextView {
-	func isForwardDirection(_ direction: TextDirection) -> Bool {
-		switch direction {
-		case .storage(.forward):
-			return true
-		case .layout(.right):
-			return userInterfaceLayoutDirection == .leftToRight
-		case .layout(.left):
-			return userInterfaceLayoutDirection == .rightToLeft
-		default:
-			return false
-		}
-	}
-}
-
 @MainActor
 public final class TextInputStringTokenizer {
 	private let textInput: NSTextView
@@ -30,6 +15,25 @@ extension TextInputStringTokenizer : TextTokenizer {
 	public typealias Position = TextPosition
 
 	public func position(from position: Position, toBoundary granularity: TextGranularity, inDirection direction: TextDirection) -> Position? {
+		guard let position = position as? UTF16TextPosition else { return nil }
+
+		let maximum = self.textInput.textStorage?.length ?? 0
+		let forward = direction.textStorageDirection(with: textInput.userInterfaceLayoutDirection) == .forward
+
+		switch (granularity, direction) {
+		case (.character, .storage(.forward)):
+			return position.offsetPosition(by: 1, maximum: maximum)
+		case (.character, .storage(.backward)):
+			return position.offsetPosition(by: -1, maximum: maximum)
+
+		case (.character, .layout(.left)), (.character, .layout(.right)):
+			let offset = forward ? 1 : -1
+
+			return position.offsetPosition(by: offset, maximum: maximum)
+		default:
+			break
+		}
+
 		return nil
 	}
 
@@ -41,7 +45,7 @@ extension TextInputStringTokenizer : TextTokenizer {
         guard let position = position as? UTF16TextPosition else { return false }
 
         let string = (textInput.attributedString().string as NSString)
-        let forward = textInput.isForwardDirection(direction)
+		let forward = direction.textStorageDirection(with: textInput.userInterfaceLayoutDirection) == .forward
         let start = forward ? max(position.value - 1, 0) : 0
         let end = forward ? string.length : min(position.value + 1, string.length)
         let options: NSString.EnumerationOptions

Tests/LigatureTests/PlatformTests.swift

@@ -14,3 +14,30 @@ final class PlatformTests: XCTestCase {
 		XCTAssertEqual(right.textStorageDirection(with: .rightToLeft), .backward)
 	}
 }
+
+#if os(macOS)
+import AppKit
+
+@MainActor
+extension PlatformTests {
+	func testPositionOffset() throws {
+		let view = NSTextView()
+
+		view.text = "abcdef"
+
+		let position = try XCTUnwrap(view.position(from: view.beginningOfDocument, offset: 3))
+
+		XCTAssertEqual(view.offset(from: view.beginningOfDocument, to: position), 3)
+	}
+
+	func testMakeTextRange() throws {
+		let view = NSTextView()
+
+		view.text = "abcdef"
+
+		let position = try XCTUnwrap(view.position(from: view.beginningOfDocument, offset: 3))
+		_ = try XCTUnwrap(view.textRange(from: view.beginningOfDocument, to: position))
+	}
+}
+
+#endif

Tests/LigatureTests/TextTokenizerTests.swift

@@ -1,5 +1,5 @@
 import XCTest
-#if canImport(AppKit) && !targetEnvironment(macCatalyst)
+#if os(macOS)
 import AppKit
 
 typealias TextView = NSTextView
@@ -22,15 +22,15 @@ import Ligature
 
 final class TextTokenizerTests: XCTestCase {
 	@MainActor
-	func testTextInputTokenizerFallback() throws {
+	func testIsPositionByWord() throws {
 		let input = TextView()
 		input.text = "abc def"
 
 		let tokenzier = TextInputStringTokenizer(textInput: input)
 
 		let start = input.beginningOfDocument
 		let middle = try XCTUnwrap(input.position(from: start, offset: 1))
-		let end = try XCTUnwrap(input.position(from: start, offset: 3))
+		let end = try XCTUnwrap(input.position(from: start, offset: 7))
 
 		XCTAssertFalse(tokenzier.isPosition(start, atBoundary: .word, inDirection: .storage(.forward)))
 		XCTAssertTrue(tokenzier.isPosition(start, atBoundary: .word, inDirection: .storage(.backward)))
@@ -41,4 +41,34 @@ final class TextTokenizerTests: XCTestCase {
 		XCTAssertTrue(tokenzier.isPosition(end, atBoundary: .word, inDirection: .storage(.forward)))
 		XCTAssertFalse(tokenzier.isPosition(end, atBoundary: .word, inDirection: .storage(.backward)))
 	}
+
+	@MainActor
+	func testPositionByCharacter() throws {
+		let input = TextView()
+		input.text = "abc def"
+
+		let tokenzier = TextInputStringTokenizer(textInput: input)
+
+		let start = input.beginningOfDocument
+		let end = try XCTUnwrap(input.position(from: start, offset: 7))
+
+		XCTAssertNil(tokenzier.position(from: start, toBoundary: .character, inDirection: .storage(.backward)))
+		XCTAssertNil(tokenzier.position(from: start, toBoundary: .character, inDirection: .layout(.left)))
+
+		let pos1 = try XCTUnwrap(tokenzier.position(from: start, toBoundary: .character, inDirection: .storage(.forward)))
+		XCTAssertEqual(input.offset(from: start, to: pos1), 1)
+
+		let pos2 = try XCTUnwrap(tokenzier.position(from: start, toBoundary: .character, inDirection: .layout(.right)))
+		XCTAssertEqual(input.offset(from: start, to: pos2), 1)
+
+		XCTAssertNil(tokenzier.position(from: end, toBoundary: .character, inDirection: .storage(.forward)))
+		XCTAssertNil(tokenzier.position(from: end, toBoundary: .character, inDirection: .layout(.right)))
+
+		let pos3 = try XCTUnwrap(tokenzier.position(from: end, toBoundary: .character, inDirection: .storage(.backward)))
+		XCTAssertEqual(input.offset(from: start, to: pos3), 6)
+
+		let pos4 = try XCTUnwrap(tokenzier.position(from: end, toBoundary: .character, inDirection: .layout(.left)))
+		XCTAssertEqual(input.offset(from: start, to: pos4), 6)
+
+	}
 }