Custom Cut, Copy & Paste operations for WKWebView

Question

I am developing a Cocoa application to wrap a JavaScript web application I have developed that provides editing of SVG graphics. I have the following question, which is motivated by a desire to customize the Cut, Copy and Paste operations and their associated menu items.

How can I either:

• substitute my own responder in place of WKWebView or
• customize its responses to validateMenuItem: and the cut:, copy: and paste: selectors?

I am particularly interested in solutions that retain the useful WKWebView functionality of providing Cut, Copy and Paste for text fields.

Any help would be much appreciated. Detail follows.

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The purpose of my Cocoa wrapper is threefold:

1. to provide persistence
2. to provide clipboard integration
3. to provide printing

I've achieved 1, but am blocked on 2 and 3; this question is about 2.

Specifically, I cannot get the framework to call any implementation of validateMenuItem: that I provide — as a result, I have no control over when the Cut, Copy or Paste menu items are available for the user to select.

I have tried the following:

1. mark my NSViewController subclass as accepting first responder and override validateMenyItem: there — my implementation was never called
2. subclass WKWebView and override validateMenuItem: — my implementation was never called
3. subclass NSWindowController and override validateMenuItem: — my implementation was never called

Now, my wrapped web app has some text fields. When I give one of those focus and when it is appropriate (text is on the clipboard; I highlight some text), the Cut, Copy and Paste options in my Edit menu automagically activate. They even work. (I like this functionality, and would like to retain it.) I therefore suspect that what is happening is that the WKWebView, as my current first responder, is intercepting any call to validateMenuItem: along the responder chain. But I also need to be able to activate menu items according to other states in my wrapped web app — for example, when the user selects an SVG graphic.

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Update

I have done additional digging, in trying to figure out a solution to my problem. In my WKWebView subclass, I added a custom @IBAction. I created a menu item for it on my story board and wired the menu item to FirstResponder, choosing my new action.

And my validateMenuItem: on my WKWebView subclass was called. But only for that new selector, not for the copy: selector associated with the @IBAction that I had previously added to my WKWebView subclass.

Now, my copy: method, marked with @IBAction and having the method signature for things that Interface Builder (or whatever it's called these days) is able to use, is not marked override. When I tried to mark it override, I got an error. Apparently, WKWebView does not provide a copy:id method — even though it provides Copy functionality and handles the menu item correctly, when text in a text field is selected.

So it appears that, somehow, WKWebView automatically (and always) handles validation for certain selectors typically bound to menus — specifically, cut:, copy: and paste:. Moreover, subclassing WKWebView and overriding validateMenuItem: is insufficient to interrupt/take control over this default behavior. Which seems odd.

But from reading other posts on WKWebView on StackOverflow, I am aware that WKWebView is actually quite a complex piece of functionality. Of particular interest/concern to me is that WKWebView actually runs the web content in a separate process. I therefore wonder if something related to that separate process is responsible for menu validation and handling cut:, copy: and paste: — something internal to the framework and to which I don't have access.

I'm still hoping for a solution. Hopefully the above update will prove useful.

Answer 1

... 5 years later....

Please have a look at my own answer to another problem: Manipulate paste content in WKWebView this solution involves method Swizzling and probably can easily solve your problem too.

Answer 2

Oddly enough, I was also looking at porting over a vector design tool to the Mac via WKWebView and encountered the same problem. It looks like you can actually control the cut/copy/paste menu items from inside JavaScript. If you add beforecopy and beforecut event handlers and preventDefault() them, then the cut and copy menu items will be enabled. I can't seem to enable the paste menu item though. I think that may be due to a long-running bug in WebKit. You can still ⌘-V on the keyboard, and the paste will still happen because in that case, WebKit will skip calling beforepaste and just trigger the paste event directly. I just can't figure out enabling the paste menu item. As a workaround, I've created a "fake" Paste menu option that doesn't go to the normal paste: selector but to my own selector that the WKWebView won't intercept.