Implement WebviewPanel.reveal()

[vparfonov]

Need for #4339

[benoitf]

@vparfonov FYI the Signed-Off is invalid (eclipsefdn/eca) check

[benoitf]

👍

[akosyakov]

@vparfonov How can one verify that it works? Do you have a VS Code extension?

[vparfonov]

@akosyakov
This demo from master
This from my branch

I used this sample for testing https://github.com/Microsoft/vscode-extension-samples/tree/master/webview-sample

[akosyakov]

It does not seem to receive focus, if a widget has focus its tab should be highlighted blue. It happens automatically when any child node of a widget is document.activeElement.

[akosyakov]

https://github.com/theia-ide/theia/blob/48743de06e33ea812dddc3b70b0900ea9f77c754/packages/plugin-ext/src/main/browser/webviews-main.ts#L89-L92 is bogus as well, should be aligned.

I think focus function should not be exposed out of Webview and only used in onActivateRequest.

[vparfonov]

is bogus as well, should be aligned.

Yes looks like you are right, i will remove this code. Thanks

[akosyakov]

I've modified the sample example with input field and it does not work. I will open an alternative PR to solve it.