feat: enhance accessibility support in STTextView

The commit extends NSAccessibilityProtocol implementation in STTextView by adding
support for NSAccessibilityStaticText and NSAccessibilityNavigableStaticText
protocols. It implements frame, line positioning, and range methods to improve
screen reader compatibility and navigation capabilities within text content.

Author: krzyzanowskim

Sources/STTextViewAppKit/STTextView+NSAccessibilityProtocol.swift

@@ -2,7 +2,9 @@
 //  https://github.com/krzyzanowskim/STTextView/blob/main/LICENSE.md
 
 import AppKit
+import STTextKitPlus
 
+/// NSAccessibilityProtocol
 extension STTextView  {
 
     open override func isAccessibilityElement() -> Bool {
@@ -25,21 +27,26 @@ extension STTextView  {
         NSLocalizedString("Text Editor", comment: "")
     }
 
-    open override func accessibilityValue() -> Any? {
-        text
+    open override func accessibilityNumberOfCharacters() -> Int {
+        text?.count ?? 0
     }
 
-    open override func setAccessibilityValue(_ accessibilityValue: Any?) {
-        guard let string = accessibilityValue as? String else {
-            return
-        }
+    open override func accessibilitySelectedText() -> String? {
+        textLayoutManager.textSelectionsString()
+    }
 
-        self.text = string
+    open override func accessibilitySelectedTextRange() -> NSRange {
+        selectedRange()
     }
 
-    open override func accessibilityAttributedString(for range: NSRange) -> NSAttributedString? {
-        attributedSubstring(forProposedRange: range, actualRange: nil)
+    open override func isAccessibilityFocused() -> Bool {
+        isFirstResponder && isSelectable
     }
+}
+
+extension STTextView  {
+
+    // NSAccessibilityStaticText
 
     open override func accessibilityVisibleCharacterRange() -> NSRange {
         if let viewportRange = textLayoutManager.textViewportLayoutController.viewportRange {
@@ -49,27 +56,61 @@ extension STTextView  {
         return NSRange()
     }
 
-    open override func accessibilityString(for range: NSRange) -> String? {
-        attributedSubstring(forProposedRange: range, actualRange: nil)?.string
+    open override func setAccessibilitySelectedTextRange(_ accessibilitySelectedTextRange: NSRange) {
+        guard let textRange = NSTextRange(accessibilitySelectedTextRange, in: textContentManager) else {
+            assertionFailure()
+            return
+        }
+        setSelectedTextRange(textRange, updateLayout: true)
     }
 
-    open override func accessibilityNumberOfCharacters() -> Int {
-        text?.count ?? 0
+    open override func accessibilityAttributedString(for range: NSRange) -> NSAttributedString? {
+        attributedSubstring(forProposedRange: range, actualRange: nil)
     }
 
-    open override func accessibilitySelectedText() -> String? {
-        textLayoutManager.textSelectionsString()
+    open override func accessibilityValue() -> Any? {
+        text
     }
 
-    open override func accessibilitySelectedTextRange() -> NSRange {
-        selectedRange()
+    open override func setAccessibilityValue(_ accessibilityValue: Any?) {
+        guard let string = accessibilityValue as? String else {
+            return
+        }
+
+        self.text = string
     }
 
-    open override func setAccessibilitySelectedTextRange(_ accessibilitySelectedTextRange: NSRange) {
-        if let textRange = NSTextRange(accessibilitySelectedTextRange, in: textContentManager) {
-            setSelectedTextRange(textRange, updateLayout: true)
-        } else {
-            assertionFailure()
+    // NSAccessibilityNavigableStaticText
+
+    open override func accessibilityFrame(for range: NSRange) -> NSRect {
+        guard let textRange = NSTextRange(range, in: textContentManager) else {
+            return .zero
+        }
+        return textLayoutManager.textSegmentFrame(in: textRange, type: .standard) ?? .zero
+    }
+
+    open override func accessibilityLine(for index: Int) -> Int {
+        guard let location = textContentManager.location(at: index),
+              let position = textContentManager.position(location)
+        else {
+            return 0
+        }
+        return position.row
+    }
+
+    open override func accessibilityRange(forLine line: Int) -> NSRange {
+        guard let location = textContentManager.location(line: line),
+              let textElement = textContentManager.textElements(for: NSTextRange(location: location)).first,
+              let textElementRange = textElement.elementRange
+        else {
+            return .notFound
         }
+
+        return NSRange(textElementRange, in: textContentManager)
     }
+
+    open override func accessibilityString(for range: NSRange) -> String? {
+        attributedSubstring(forProposedRange: range, actualRange: nil)?.string
+    }
+
 }