Possible fix for #3455: Compare EditorIdentity when handling window.onDidChangeTextEditorSelection.

[coddingtonbear]

What this PR does / why we need it:

This PR changes two things:

• Alters EditorIdentity such that it uses the ViewColumn of the editor for differentiating between multiple editors open to the same file using changes long ago proposed by @lukaszb (thanks for posting a patch!).
• Updates our handler for vscode.window.onDidChangeTextEditorSelection such that it uses that EditorIdentity when deciding whether to handle an incoming event instead of simply comparing documents.

Which issue(s) this PR fixes

#3455

Special notes for your reviewer:

[jpoon]

Iirc, there is a case where this breaks undo. #2688

[coddingtonbear]

Yes! I have seen a situation in which it seems like the undo history is shared between panes now, and when undoing something in one pane, it might undo an action that took place in the other. I wasn't immediately sure that that was a regression this change created, but am ?glad to hear that you can confirm that it is.

Would it be your opinion that this approach toward solving this problem is unworkable (meaning, I shouldn't bother spending time figuring out how vscode-vim handles undo queues), or is it worthwhile to keep digging into things to see if I can fix undo handling with the changes in this PR?

[jpoon]

This was an old issue so not sure if I recall the details but the current behaviour was the lesser of two evils given the limitation with the vscode API there's an upstream issue somewhere (On my phone so can't link).

At the moment, we only have one notion of an editor id but I feel like we might need to split this up as there Is state specific to:

• Unique to the text editor -- cursor position, movements, action history
• Unique to the file -- undo/redo

[coddingtonbear]

Just to be clear, if we're expecting undo/redo to be shared among all open editors to the same file -- and in hindsight, I can't imagine it any other way -- I think this is operating as expected for me so far in the ways you've described above.

The weird thing I do think isn't working is that search/replace within a visual selection isn't working. I haven't dug into it very deeply, but given the things this PR changed, I can think of several ideas about what might've become broken and will try to find a little time to dig deeper this week.

[J-Fields]

Hey @coddingtonbear, thanks for this PR!
I'm seeing some misbehavior with undo/redo. Here's an example:

1. Open new document
2. :vsp
3. o1<esc>o2<esc>o3<esc>
4. Undo/redo to see they operate on single line additions
5. Go to other side and see undo undoes all 3 lines
6. Try to redo on first side - doesn't work

[coddingtonbear]

Oh, sure, this totally doesn't work in the latest version of vscodevim, @J-Fields, and I don't have a lot of time to update it, so I think I'm just going to close this PR 🤷‍♂️ .