Unable to use shortcuts like Cmd+A, Cmd+C, Cmd+V inside an iframe inside a webview on macOS

[DanTup]

Edit: This is unrelated to clipboard operations, because Cmd+A doesn't work either.

I created a simple repro here that opens an iframe inside a webview:

https://github.com/DanTup/vs-code-webview-copy-paste

The webview contains a text input. You cannot copy, paste, or even Select All inside that text input.

(Original post below)

---

I'm embedding an app inside a webview using an iframe (avoiding the iframe is not likely feasible). In order to have VS Code keyboard shortcuts still work, keypresses are passed over using the code here:

• macOS: some commands no longer work inside iframe inside webview #65452 (comment)
• macOS: some commands no longer work inside iframe inside webview #65452 (comment)

This works for many keypress (for example opening the command palette), however it's not possible to use Cmd+C to copy to the clipboard. Edit -> Copy works as expected.

It's not clear if there needs to be some extra handling in the webiew or iframe to make this work, or if it needs support from VS Code.

[DanTup]

To reproduce:

• check out the webview sample from https://github.com/microsoft/vscode-extension-samples/tree/main/webview-sample
• remove the CSP header and add an iframe that has code to pass keypresses up to the webview and to dispatch the event:

  <iframe src="https://blog.dantup.com/testing/vscode_iframe.htm" style="width: 600px; height: 600px;"></iframe>
  <script>
  	window.addEventListener("message", (e) => {
  	window.dispatchEvent(new KeyboardEvent('keydown', JSON.parse(e.data)));
  	}, false);
  </script>
  

Run the extension and use the command to open the webview. Confirm Cmd+Shift+P opens the command palette even when focus is in the webview. Highlight some text and press Cmd+C, and note that the selected text was not copied to the clipboard.

[tamuratak]

We can access navigator.clipboard on webview:

vscode/src/vs/workbench/contrib/webview/browser/webviewElement.ts

Line 375 in 0e52275

element.setAttribute('allow', 'clipboard-read; clipboard-write;');

Instead of calling window.dispatchEvent, we can call window.navigator.clipboard.writeText. We also have to send a text to copy from the child iframe.

Interestingly, we cannot access navigator.clipboard inside the child iframe in the webview even if we add allow="clipboard-read; clipboard-write;" to the iframe tag in the parent webview. This might be related to the following issue:

• https://bugs.chromium.org/p/chromium/issues/detail?id=1074489