[Super Clipboard][iOS] - Swizzle Flutter method to say that we can paste even when binary data is on the clipboard (#2903)

Author: matthew-carroll

super_editor_clipboard/ios/Classes/SuperEditorClipboardPlugin.swift

@@ -16,7 +16,9 @@ public class SuperEditorClipboardPlugin: NSObject, FlutterPlugin {
     let instance = SuperEditorClipboardPlugin()
     registrar.addMethodCallDelegate(instance, channel: channel)
 
+    // Swizzle both the action execution (paste) and the validation (canPerformAction)
     swizzleFlutterPaste()
+    swizzleCanPerformAction()
   }
 
   public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
@@ -33,63 +35,127 @@ public class SuperEditorClipboardPlugin: NSObject, FlutterPlugin {
     }
   }
 
+  // MARK: - Swizzling Logic
+
   private static func swizzleFlutterPaste() {
-    // 1. Locate the private Flutter engine class
-    guard let flutterClass = NSClassFromString("FlutterTextInputView") else {
-      log("RichPastePlugin: Could not find FlutterTextInputView")
+    swizzle(
+        clsName: "FlutterTextInputView",
+        originalSelector: #selector(UIResponder.paste(_:)),
+        customSelector: #selector(customPaste(_:))
+    )
+  }
+
+  private static func swizzleCanPerformAction() {
+    swizzle(
+        clsName: "FlutterTextInputView",
+        originalSelector: #selector(UIResponder.canPerformAction(_:withSender:)),
+        customSelector: #selector(customCanPerformAction(_:withSender:))
+    )
+  }
+
+  private static func swizzle(clsName: String, originalSelector: Selector, customSelector: Selector) {
+    guard let flutterClass = NSClassFromString(clsName) else {
+      log("Could not find \(clsName)")
       return
     }
 
-    let originalSelector = #selector(UIResponder.paste(_:))
-    let swizzledSelector = #selector(customPaste(_:))
-
-    // 2. Get the methods
     guard let originalMethod = class_getInstanceMethod(flutterClass, originalSelector),
-          let swizzledMethod = class_getInstanceMethod(SuperEditorClipboardPlugin.self, swizzledSelector) else {
+          let swizzledMethod = class_getInstanceMethod(SuperEditorClipboardPlugin.self, customSelector) else {
+      log("Could not find methods to swizzle for \(clsName)")
       return
     }
 
-    // 3. Inject our custom method into the Flutter engine class
+    // Add the custom method to the Flutter class
     let didAddMethod = class_addMethod(
       flutterClass,
-      swizzledSelector,
+      customSelector,
       method_getImplementation(swizzledMethod),
       method_getTypeEncoding(swizzledMethod)
     )
 
     if didAddMethod {
-      // 4. Swap the pointers
-      let newMethod = class_getInstanceMethod(flutterClass, swizzledSelector)!
+      // Exchange implementations so 'originalSelector' calls our custom code,
+      // and 'customSelector' calls the original code.
+      let newMethod = class_getInstanceMethod(flutterClass, customSelector)!
       method_exchangeImplementations(originalMethod, newMethod)
+      log("Successfully swizzled \(originalSelector) in \(clsName)")
+    } else {
+        log("Failed to add method \(customSelector) to \(clsName)")
     }
   }
 
-  // This method is "moved" into FlutterTextInputView at runtime.
-  // 'self' inside this method will actually be the FlutterTextInputView instance.
+  // MARK: - Custom Implementations
+
+  /// This method replaces `paste(_:)` at runtime.
   @objc func customPaste(_ sender: Any?) {
     if (!SuperEditorClipboardPlugin.doCustomPaste) {
       SuperEditorClipboardPlugin.log("Running regular Flutter paste")
-      // FALLBACK:
-      // This calls the ORIGINAL paste logic.
-      // Because we swapped the methods, calling 'customPaste' on 'self'
-      // now triggers the engine's original 'insertText' flow.
+      // FALLBACK: Call original implementation (which is now mapped to customPaste)
       if self.responds(to: #selector(customPaste(_:))) {
         self.perform(#selector(customPaste(_:)), with: sender)
       }
-
-      return;
+      return
     }
 
     SuperEditorClipboardPlugin.log("Running custom paste")
     SuperEditorClipboardPlugin.channel?.invokeMethod("paste", arguments: nil)
   }
 
+  /// This method replaces `canPerformAction(_:withSender:)` at runtime.
+  @objc func customCanPerformAction(_ action: Selector, withSender sender: Any?) -> Bool {
+    let isPasteAction = action == #selector(UIResponderStandardEditActions.paste(_:))
+
+    // 1. If it is the PASTE action AND we are in custom mode, check our broader conditions.
+    if isPasteAction && SuperEditorClipboardPlugin.doCustomPaste {
+        // Check for ANY pasteable content (Images, Colors, URLs, Strings)
+        // Note: Flutter only checks `hasStrings`.
+        if UIPasteboard.general.hasStrings ||
+           UIPasteboard.general.hasImages ||
+           UIPasteboard.general.hasURLs ||
+           UIPasteboard.general.hasColors {
+            return true
+        }
+    }
+
+    // 2. Otherwise (or if the custom check failed), fall back to the ORIGINAL logic.
+    // Because we exchanged implementations, calling 'customCanPerformAction' here
+    // actually invokes the original Flutter engine logic.
+
+    // We cannot use 'perform' for Bool return types, so we use IMP casting.
+    return SuperEditorClipboardPlugin.callOriginalCanPerformAction(
+        instance: self,
+        selector: #selector(customCanPerformAction(_:withSender:)),
+        action: action,
+        sender: sender
+    )
+  }
+
+  // MARK: - Helpers
+
+  /// Safely invokes the original implementation of `canPerformAction` (which is now swapped).
+  private static func callOriginalCanPerformAction(instance: Any, selector: Selector, action: Selector, sender: Any?) -> Bool {
+    guard let method = class_getInstanceMethod(object_getClass(instance), selector) else {
+        return false
+    }
+
+    let imp = method_getImplementation(method)
+
+    // Define the C function signature for (BOOL)objc_msgSend(id, SEL, SEL, id)
+    typealias CanPerformActionFunction = @convention(c) (AnyObject, Selector, Selector, Any?) -> Bool
+
+    let originalFunction = unsafeBitCast(imp, to: CanPerformActionFunction.self)
+
+    // 'instance' is 'self' (FlutterTextInputView)
+    // 'selector' is the selector triggering this IMP (customCanPerformAction)
+    // 'action' is the argument (e.g., paste:)
+    return originalFunction(instance as AnyObject, selector, action, sender)
+  }
+
   public static let isLoggingEnabled = false
 
   internal static func log(_ message: String) {
     if isLoggingEnabled {
       print("[SuperEditorClipboardPlugin] \(message)")
     }
   }
-}
-
+}