createWebviewPanel doesn't fire WebviewPanelOnDidChangeViewStateEvent to other webviews

[jdoklovic]

• VSCode Version: 1.32.3
• OS Version: ubuntu 18.04

Steps to Reproduce:

1. create a webview
2. add an onDidChangeViewState handler
3. output a log message with it's visibility when it receives the event
4. create a different webview that also logs visibility in it's onDidChangeViewState handler

Expected log output:
create first webview ->

• "webview one visible: true"

create second webview ->

• "webview two visible: true"
• "webview one visible: false"

Actual log output:
create first webview ->

• "webview one visible: true"

create second webview ->

• "webview two visible: true"

Note: After both are open, if you click between their tabs a couple of times, the events start working properly.

[vscodebot]

(Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• Crash in webview render process when webview creates a web worker. (#70711)
• Cannot Capture File->Save menu option when using a webview (#60801)
• retainContextWhenHidden should restore focus within the webview as well (#48604)
• feature request: API to set URL of WebView (#70339)
• Need an event to signal the user is closing a webview window (#66939)

[jdoklovic]

@mjbvz
I've created a repo that re-creates this issue here:
https://github.com/atlassian/webvieweventtest

just follow the readme.