Prevent saving when some file properties change

CHDataManagement/Model/Content.swift

@@ -47,6 +47,9 @@ final class Content: ObservableObject {
 
     var errorCallback: ((StorageError) -> Void)?
 
+    /// A cache of file sizes
+    private var fileSizes: [String: Int] = [:]
+
     init() {
         let settings = Settings.default
         self.settings = settings
@@ -196,4 +199,26 @@ final class Content: ObservableObject {
     func setLastSaveTimestamp() {
         self.lastSave = .now
     }
+
+    // MARK: File sizes
+
+    func size(of file: String) -> Int? {
+        fileSizes[file]
+    }
+
+    func cache(size: Int?, of file: String) {
+        fileSizes[file] = size
+    }
+
+    // MARK: Image dimensions
+
+    private var imageDimensions: [String: CGSize] = [:]
+
+    func dimensions(of image: String) -> CGSize? {
+        imageDimensions[image]
+    }
+
+    func cache(dimensions: CGSize?, of image: String) {
+        imageDimensions[image] = dimensions
+    }
 }