Undo/Redo shortcuts don't work for theia extension custom editor widget

[Hanksha]

This is a continuation of the discussion on this issue #9344 .

[vince-fugnitto]

Is there an issue with providing end-users the possibility to have more control over how and when to perform undo for your custom-view? In the following #9344 (comment) you mentioned that the monaco undo takes priority over your custom handler, so it seems you already have a handler present?

[Hanksha]

Yes I already have an handler registered for the "core.undo" command (and the "undo" command since I found out that the one called by the keybinding). The problem is that since the handler registered by monaco-command is always enabled (even when there are no text editors open) then my handler never gets called.

[vince-fugnitto]

You mean a when clause to the keybinding? Because I don't see a when on the CommandHandler interface.

Yes, when registering the keybinding add a when clause that is enabled when your view is visible. It should take priority over monaco which does not have one. It is at least something to try.

[Hanksha]

Yes but that would mean registering a third undo and redo command (registering it for the same command won't help). I have a dozen custom editors across multiple extensions so the when clause would be pretty long.

From a design perspective you should have one command that represent a common action like undo, redo, copy, paste etc. and have one keybinding for it and multiple handlers only enabled correctly when they should. Then if you want a different keybinding for a specific editor you register another keybinding with a different "when" but for the same command.

I can try that workaround but I think it could be better to fix it in theia directly. I also found a workaround by filtering out "MonacoEditorCommandHandlers" via "FilterContribution" and registering my own implementation, that's likely to break though.

[vince-fugnitto]

As I mentioned before it's a little hard to help as I can't actually see the code, if you can provide a minimal example that is similar to what you're doing that would help. For example, what does your custom handler look like?

In this case the monaco undo is correctly enabled (as it applies to focused or last focused editors) but you want to override it. A way forward can be to provide your own keybinding rule that applies to your custom-views (could be a base class you extend for all your custom-editors) only.

[Hanksha]

No it's always enabled, even without any text editors focused or opened, it returns true as a default, see https://github.com/eclipse-theia/theia/blob/master/packages/monaco/src/browser/monaco-command.ts#L179

[vince-fugnitto]

I'm not sure why by default it is true if you want to investigate a bit but I believe undo is very much tied to editors (#2239). You may be interested in something that VS Code implemented https://github.com/microsoft/vscode/pull/98288/files if you don't want to add the workaround I mentioned.