What is the correct way to retain a reference to a specific tab?

[csnover]

Hi,

I am writing a feature for an extension where I want to display some counterpart content based on whatever tab is active in another tab group. I want to reuse the same tab to display different counterpart content as the active tab changes. The counterpart content displayed may be a TextEditor or it may be a Webview. (Discussion #74 is vaguely relevant here as my first thought was to create a custom editor that embeds a TextEditor, but I guess that is also not possible.)

Since I don’t see any VSCode API for explicitly managing the content of a tab, I currently open a new TextEditor by showTextDocument or WebviewPanel by createWebviewPanel, listen on onDidChangeTabs until I see a newly opened tab to retain, and finally call close on the previously stored tab so it is “as if” there is only a single tab.

This is not a great approach, particularly since the UI ends up drawing two tabs for a frame (which is at least better than VSCode collapsing the view column for a frame by removing the old tab first), but it seems to be the only possible way to do this and it works “fine”.

Where this approach fails completely, though, is when a user opens a new tab group. For some reason I do not understand (since it shouldn’t be necessary to do this—even if backing objects change, the properties are all accessors?), this action causes multiple invalidations of existing Tab objects, even though none of the tabs have been closed (which is the only thing I can find in the documentation that’s stated to cause invalidation).

The first invalidation of Tab objects seems to occur immediately when the new tab group is added. But then, after detecting that the retained Tab was invalidated (by receiving a TabGroupChangeEvent with opened.length) and recovering a replacement (by crossing my fingers that indexes into tabGroups.all are stable), the recovered Tab object is itself invalidated by some later event in the sequence of events.

What are extension authors supposed to do to track a tab like this? I can give the WebviewPanel a unique ID and recover its tab with a brute force search of tabGroups.all, but there’s no way to recover the tab from a TextEditor: it doesn’t expose any reference to its tab, and multiple TextEditors can share documents with the same URI, so it’s also possible for multiple tabs to have the same input.uri. I don’t think I can use a custom URI scheme or extra fragment to do that either, because if the user already has the counterpart content open in another tab, that would cause two unique TextDocuments to be open instead of one for the same file, which is not desired. I don’t think I can avoid retaining the Tab object, because if a user manually closes the tracked tab, the only way to tell that is by seeing a tab closed event and checking to see if the tab is the same as the retained one by identity. I can’t access the internal tabId. So I am pretty much out of ideas, short of crossing my fingers that tab group indexes in tabGroups.all are stable and also retaining the tab group’s index.

Thanks,

[isidorn]

We have introduced the Tab API in the meantime. Did you have a chance to try it out? If yes, is there something that is missing for your use case?

[olguzzar]

@csnover following up on this thread to see if the Tab API had what you were looking for. We will close this discussion in 7 days if there is no new activity.

[theReynald]

Closing due to inactivity. Reopen if needed.

[csnover]

Yep, that’s fine. Getting a response after four months that goes “hey, have you tried using this API that you already mentioned using in your question? Are there things that you have described in your question as missing from the API that are missing from this API?”, and then having that marked as the answer, was real weird. I’ve got no plan to work on vscode features in the future, so keeping this closed as unanswered is fine.