Add registerWindowTitleVariable command

[BABA983]

Close #202991

Usage in extension

vscode.commands.executeCommand('registerWindowTitleVariable', key, value)

settings.json

"window.title": "${windowTitleVariable.aa}"

window-title-variable-demo.mp4

[benibenj]

@BABA983 any reason this is still a draft?

[BABA983]

@BABA983 any reason this is still a draft?

I was thinking should we separate the behaviour into 2 commands? e.g. registerWindowTitleVariable and setWindowTitleVariable. Maybe just 1 command is good enough for the simplicity.

[benibenj]

Both options are not optimal, but having just one might be the better choice. If we have a register and a set command, we can easily detect if two extensions are creating the same variable with the same name and can log this, however, this would probably also mean we would have to support a way to unregister a variable as an extension might be enabled and disabled multiple times. I don't really want to have 3 commands for this, so I think having only a set command is good enough.

[benibenj]

@bpasero can you have a glance at this PR?

[bpasero]

I think the title variable service thing is overkill unless we plan on using it somewhere else, so in that case we could just inline the command into the title bar part?

[BABA983]

Thanks for the feedback, I have addressed the issues mentioned in the previous review. Could you please take a moment to review the changes again?

[benibenj]

@BABA983 we decided that it would make sense for an extension to create the context key and then provide it to the registerWindowTitleVariable command. I made some changes to support this behaviour. Here is an example use case:

export function activate(context: vscode.ExtensionContext) {
    setInterval(() => 
        vscode.commands.executeCommand('setContext', 'timeNowContextKey', new Date().toLocaleTimeString()),
        1000
    );
    vscode.commands.executeCommand('registerWindowTitleVariable', 'timeNow', 'timeNowContextKey');
}

[bpasero]

I went ahead and did the changes I had in mind because I think we spend a bit too much time engineering this.