perf(editor): idle the hidden fold ribbon and use NSString equality in binding sync

Author: datlechin

LocalPackages/CodeEditSourceEditor/Sources/CodeEditSourceEditor/Gutter/GutterView.swift

@@ -78,6 +78,9 @@ public class GutterView: NSView {
     public var showFoldingRibbon: Bool = true {
         didSet {
             foldingRibbon.isHidden = !showFoldingRibbon
+            if showFoldingRibbon {
+                foldingRibbon.model?.refresh()
+            }
         }
     }
 

LocalPackages/CodeEditSourceEditor/Sources/CodeEditSourceEditor/LineFolding/Model/LineFoldModel.swift

@@ -57,6 +57,11 @@ class LineFoldModel: NSObject, NSTextStorageDelegate, ObservableObject {
         foldCache.folds(in: range)
     }
 
+    /// Recomputes folds for the whole document. Used to catch up after the ribbon has been hidden and is shown again.
+    func refresh() {
+        textChangedStreamContinuation.yield()
+    }
+
     func textStorage(
         _ textStorage: NSTextStorage,
         didProcessEditing editedMask: NSTextStorageEditActions,
@@ -67,6 +72,9 @@ class LineFoldModel: NSObject, NSTextStorageDelegate, ObservableObject {
             return
         }
         foldCache.storageUpdated(editedRange: editedRange, changeInLength: delta)
+        // Recalculating folds walks the whole document. Skip it while the ribbon is hidden; `refresh()` rebuilds when
+        // it is shown again.
+        guard foldView?.isHidden != true else { return }
         textChangedStreamContinuation.yield()
     }
 

LocalPackages/CodeEditSourceEditor/Sources/CodeEditSourceEditor/SourceEditor/TextBindingSync.swift

@@ -77,7 +77,9 @@ final class TextBindingSync {
     /// tree-sitter state for the old document and highlighting never recovers.
     func applyRepresentableText(_ newValue: String, controller: TextViewController) {
         guard !phase.isEditorChangePending else { return }
-        guard newValue != lastSyncedText else { return }
+        // Compare with NSString literal equality. The text can be multiple megabytes and bridged from NSTextStorage,
+        // so Swift's canonical `!=` walks the whole string through Unicode normalization on every representable update.
+        if let lastSyncedText, (newValue as NSString).isEqual(to: lastSyncedText) { return }
 
         writebackTask?.cancel()
         phase.applyRepresentableValue {