improve extra line fragment handling with TK2

Author: mattmassicotte

Sources/Glyph/NSTextContainer+Additions.swift

@@ -11,7 +11,7 @@ extension NSTextContainer {
 	/// - Parameter strictIntersection: If true, the result will only be rect and range strictly within the `rect` parameter. This is more expensive to compute.
 	public func enumerateLineFragments(for rect: CGRect, strictIntersection: Bool, block: (CGRect, NSRange, inout Bool) -> Void) {
 		if #available(macOS 12.0, iOS 15.0, *), let textLayoutManager {
-			textLayoutManager.enumerateLineFragments(for: rect, strictIntersection: strictIntersection, block: block)
+			textLayoutManager.enumerateLineFragments(for: rect, strictIntersection: strictIntersection, options: [.ensuresExtraLineFragment], block: block)
 
 			return
 		}

Sources/Glyph/NSTextLayoutFragment+Additions.swift

@@ -9,7 +9,9 @@ import UIKit
 extension NSTextLineFragment {
 	/// span has to be within this fragment's coordinate system
 	func rangeOfCharacters(intersecting span: Range<CGFloat>) -> NSRange? {
-		let length = characterRange.length
+		// even an empty fragment will respond to locationForCharacter(at: 0)
+		
+		let length = max(characterRange.length, 1)
 
 		var start: Int?
 
@@ -29,6 +31,11 @@ extension NSTextLineFragment {
 		}
 
 		guard let start else { return nil }
+		
+		// continuing to look here for an empty fragment doens't make sense
+		if characterRange.length == 0 {
+			return NSRange(start..<start)
+		}
 
 		var end: Int?
 

Sources/Glyph/NSTextLayoutManager+Additions.swift

@@ -211,7 +211,7 @@ extension NSTextLayoutManager {
 	public func boundingRect(for range: NSRange) -> CGRect? {
 		var rect: CGRect? = nil
 
-		enumerateTextLineFragments(in: range, options: [.ensuresLayout]) { fragment, lineFragment, lineRect, lineRange, offset in
+		enumerateTextLineFragments(in: range, options: [.ensuresLayout, .ensuresExtraLineFragment]) { fragment, lineFragment, lineRect, lineRange, offset in
 			// we need to limit the check to what overlaps `range`
 			let startIndex = max(range.lowerBound, lineRange.lowerBound) - lineRange.lowerBound
 			let endIndex = min(range.upperBound, lineRange.upperBound) - lineRange.lowerBound