Monitor app.focus() regressions

[bpasero]

I ended up only using app.focus({ steal: true }) in one place: where a second instance from the command line talks to the first instance:

vscode/src/vs/platform/launch/electron-main/launchMainService.ts

Line 79 in 3d0d50c

app.focus({ steal: true });

I was really not sure about other users of BrowserWindow.focus() so instead of blindingly adding app.focus, I would wait for regression reports from users.

It seems quite obvious to me that we would want app.focus({ steal: true }) everywhere where VSCode is possibly not in the foreground and some action triggers it:

• a second invocation from command line (this is covered)
• URL handlers (e.g. from a browser)
• a debug breakpoint (there is a setting in debug to focus window on breakpoint hit)
• drag and drop from other applications
• interacting with the macOS Dock

Some thoughts:

• it is unclear to me what app.focus means on Windows and Linux where imho we do not need to call this method at all
• should we only call this on macOS only?
• the URL handler is another potential candidate of this, but I was not sure if the application would already get focus for free when a URL is handled (e.g. this can happen when VSCode is launched from a web browser)
• we possibly need to fix debug to force focus when a breakpoint is hit
• unclear to me if interacting with DND is now broken
• unclear to me if interacting with dock is now broken

[bpasero]

Pushed 29ca95b to address 2 things:

• help debug put focus into the window (as reported in Hitting a breakpoint doesn't active window #105913)
• also steal focus when we handle a URL to ensure that the flow from clicking on a application link is not broken

As a consequence, methods for Window.focus() now have an option force: boolean to enable app.focus({ steal: true}), but we only use this on macOS where we know the flow is broken from the Electron update.