Add Demo Line Fold Provider (For Testing)

Author: thecoolwinter

Sources/CodeEditSourceEditor/Gutter/LineFolding/DefaultProviders/IndentationLineFoldProvider.swift

@@ -0,0 +1,34 @@
+//
+//  IndentationLineFoldProvider.swift
+//  CodeEditSourceEditor
+//
+//  Created by Khan Winter on 5/8/25.
+//
+
+import AppKit
+import CodeEditTextView
+
+final class IndentationLineFoldProvider: LineFoldProvider {
+    func foldLevelAtLine(_ lineNumber: Int, layoutManager: TextLayoutManager, textStorage: NSTextStorage) -> Int? {
+        guard let linePosition = layoutManager.textLineForIndex(lineNumber),
+              let indentLevel = indentLevelForPosition(linePosition, textStorage: textStorage) else {
+            return nil
+        }
+
+        return indentLevel
+    }
+
+    private func indentLevelForPosition(
+        _ position: TextLineStorage<TextLine>.TextLinePosition,
+        textStorage: NSTextStorage
+    ) -> Int? {
+        guard let substring = textStorage.substring(from: position.range) else {
+            return nil
+        }
+
+        return substring.utf16 // Keep NSString units
+            .enumerated()
+            .first(where: { UnicodeScalar($0.element)?.properties.isWhitespace != true })?
+            .offset
+    }
+}

Sources/CodeEditSourceEditor/Gutter/LineFolding/FoldingRibbonView.swift

@@ -9,6 +9,9 @@ import Foundation
 import AppKit
 import CodeEditTextView
 
+#warning("Replace before release")
+fileprivate let demoFoldProvider = IndentationLineFoldProvider()
+
 /// Displays the code folding ribbon in the ``GutterView``.
 ///
 /// This view draws its contents
@@ -50,9 +53,10 @@ class FoldingRibbonView: NSView {
     }
 
     init(textView: TextView, foldProvider: LineFoldProvider?) {
+        #warning("Replace before release")
         self.model = LineFoldingModel(
             textView: textView,
-            foldProvider: foldProvider
+            foldProvider: foldProvider ?? demoFoldProvider
         )
         super.init(frame: .zero)
         layerContentsRedrawPolicy = .onSetNeedsDisplay