Track visible viewlet

[tsmaeder]

What it does

Track active top level widget and set the relevant context keys if the visible widget is either well known or a contributed view container.
Fixes #12589

Contributed on behalf of STMicroelectronics

How to test

1. Add the following snippet to plugin-frontend-contribution.ts:

    @inject(ViewContextKeyService)
    private readonly viewContextKeys: ViewContextKeyService;

    registerCommands(commands: CommandRegistry): void {
        commands.registerCommand({
            id: 'debug context keys',
            label: 'Debug context keys'
        }, {
            execute: () => {
                console.log(`activeViewlet: ${this.viewContextKeys.activeViewlet.get()}`);
                console.log(`activePanel: ${this.viewContextKeys.activePanel.get()}`);
                console.log(`activeAuxiliary: ${this.viewContextKeys.activeAuxiliary.get()}`);
            }
        });
        ...

2. Activate various panels, remove and open views, making sure each time that the view context keys are as expected.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[msujew]

I've noticed that terminal widgets aren't tracked correctly by this change (they also weren't tracked by the old implementation). You will likely need to handle the terminal case in a special manner, since terminal widgets don't use the TERMINAL_WIDGET_FACTORY_ID as their id. For example, the first terminal the application spawns has id: 'terminal-0', with every subsequent terminal just incrementing that number.

Everything else looks fine to me though 👍

[tsmaeder]

I've noticed that terminal widgets aren't tracked correctly by this change

That's on purpose: VS Code has a single terminal view with multiple terminals running inside it. Theia has multiple terminal views. As a consequence "the terminal view is active" does not really make sense in Theia.

[msujew]

That's on purpose: VS Code has a single terminal view with multiple terminals running inside it. Theia has multiple terminal views. As a consequence "the terminal view is active" does not really make sense in Theia.

Ok, I can agree with that. However, the code itself doesn't really say that, and is more in line with my expectation. Maybe add a comment in there explaining that the current terminal widget will never hit that mapping and should be revised when a consolidated terminal widget like in vscode has been introduced to the framework?

[msujew]

Alright, looks good to me 👍