Refactor extra line fragment handling in NSTextLayoutManager and NSTe…

…xtLineFragment

This commit refines the handling of extra line fragments. The method
`extraTextLineFragment` is replaced by `extraLineTextLayoutFragment` and
`extraLineTextLineFragment`, enhancing clarity. The new properties and
methods improve the identification of extra line fragments within the
text layout system. The related `isExtraLineFragment` property has also
been added to both `NSTextLayoutFragment` and `NSTextLineFragment`,
providing a consistent way to determine when a line fragment is extra.

README.md

@@ -41,7 +41,8 @@ func attributedString(in range: NSTextRange?) -> NSAttributedString?
 func textLineFragment(at location: NSTextLocation) -> NSTextLineFragment?
 func textLineFragment(at point: CGPoint) -> NSTextLineFragment?
 
-func extraTextLineFragment() -> NSTextLineFragment?
+func extraLineTextLayoutFragment() -> NSTextLayoutFragment?
+func extraLineTextLineFragment() -> NSTextLineFragment?
 
 func location(interactingAt point: CGPoint, inContainerAt containerLocation: NSTextLocation) -> NSTextLocation?
 
@@ -59,6 +60,8 @@ var insertionPointSelections: [NSTextSelection]
 ### NSTextLayoutFragment Additions
 
 ```swift
+var isExtraLineFragment: Bool
+
 func textLineFragment(at location: NSTextLocation, in textContentManager: NSTextContentManager? = nil) -> NSTextLineFragment?
 func textLineFragment(at location: CGPoint, in textContentManager: NSTextContentManager? = nil) -> NSTextLineFragment?
 ```

Sources/STTextKitPlus/NSTextLayoutFragment.swift

@@ -35,7 +35,14 @@ import UIKit
 #endif
 
 extension NSTextLayoutFragment {
-
+
+    /// Whether the layout fragment is for the extra line fragment at the end of a document.
+    ///
+    /// The layout manager uses the extra line fragment when the last character in a document causes a line or paragraph break. This extra line fragment has no corresponding glyph.
+    public var isExtraLineFragment: Bool {
+        textLineFragments.contains(where: \.isExtraLineFragment)
+    }
+
     public func textLineFragment(at location: NSTextLocation, in textContentManager: NSTextContentManager? = nil) -> NSTextLineFragment? {
         guard let textContentManager = textContentManager ?? textLayoutManager?.textContentManager else {
             assertionFailure()

Sources/STTextKitPlus/NSTextLayoutManager.swift

@@ -36,22 +36,35 @@ import UIKit
 
 extension NSTextLayoutManager {
 
-    /// Extra line fragment.
+    /// Extra line layout fragment.
     ///
     /// Only valid when ``state`` greater than NSTextLayoutFragment.State.estimatedUsageBounds
-    @nonobjc public func extraTextLineFragment() -> NSTextLineFragment? {
-        var extraLineFragment: NSTextLineFragment?
-        enumerateTextLayoutFragments(from: textContentManager?.documentRange.endLocation, options: .reverse) { textLayoutFragment in
-            let textLineFragments = textLayoutFragment.textLineFragments
+    @nonobjc public func extraLineTextLayoutFragment() -> NSTextLayoutFragment? {
+        var extraTextLayoutFragment: NSTextLayoutFragment?
+        enumerateTextLayoutFragments(from: nil, options: .reverse) { textLayoutFragment in
             if textLayoutFragment.state.rawValue > NSTextLayoutFragment.State.estimatedUsageBounds.rawValue,
-               textLineFragments.count > 1, let lastTextLineFragment = textLineFragments.last,
-               lastTextLineFragment.characterRange.location == 0
+               textLayoutFragment.isExtraLineFragment
             {
-                extraLineFragment = lastTextLineFragment
+                extraTextLayoutFragment = textLayoutFragment
             }
             return false
         }
-        return extraLineFragment
+        return extraTextLayoutFragment
+    }
+
+    /// Extra line fragment.
+    ///
+    /// Only valid when ``state`` greater than NSTextLayoutFragment.State.estimatedUsageBounds
+    @nonobjc public func extraLineTextLineFragment() -> NSTextLineFragment? {
+        if let textLayoutFragment = extraLineTextLayoutFragment() {
+            let textLineFragments = textLayoutFragment.textLineFragments
+            if textLineFragments.count > 1, let lastTextLineFragment = textLineFragments.last,
+               lastTextLineFragment.isExtraLineFragment
+            {
+                return lastTextLineFragment
+            }
+        }
+        return nil
     }
 
 }

Sources/STTextKitPlus/NSTextLineFragment.swift

@@ -36,6 +36,14 @@ import UIKit
 
 extension NSTextLineFragment {
 
+    /// Whether the line fragment is for the extra line fragment at the end of a document.
+    ///
+    /// The layout manager uses the extra line fragment when the last character in a document causes a line or paragraph break. This extra line fragment has no corresponding glyph.
+    public var isExtraLineFragment: Bool {
+        // textLineFragment.characterRange.isEmpty the extra line fragment at the end of a document.
+        characterRange.isEmpty
+    }
+
     /// Returns a text range inside privided textLayoutFragment.
     ///
     /// Returned range is relative to the document range origin.