Mac: Bring focused windows to the foreground

[Descolada]

MakeKeyAndOrderFront does not activate a background macOS application, so Window.Focus() may fail to foreground the requested window. Activate the application first, then make the window key and bring it forward.

[cwensley]

Hey @Descolada, so I've thought about this one, and I think I'd like to see an Application.Instance.Activate() API instead of making macOS try to activate every time you focus a window. Thoughts?

[Descolada]

@cwensley interesting idea. As far as I understand, currently only macOS distinguishes active app (the overarching currently used program, claims the global menu bar at the top of the screen, owns the Dock icon indicator etc) vs focused window (where keyboard focus is). It's possible to activate an app without focusing a window, but not focusing a window without activating the app (and a window can't have keyboard focus without also being the active app). So, I think Application.Instance.Activate() would have a place to activate the app, but that would likely be a macOS-only feature (I'm not sure how that would work on other platforms - on Windows/Linux what would it activate?). Also, if Window.Focus() didn't automatically call it then the semantics of Window.Focus() would remain incorrect, because it sometimes won't bring the window to focus due to app-level activation status being wrong.

On further thought, it could perhaps be a property instead Application.Instance.Active:

• on macOS the getter would return application-level focus status (supposing it's possible to query it, I haven't looked into it), the setter would set the app-level focus
• on Windows/Linux it could answer the question whether the currently focused window belongs to our Application.Instance, but I don't think the setter would have an use

What do you think? If you think this is worth implementing then I can attempt it + change the current PR to do if (!Application.Instance.Active) Application.Instance.Active = true before attempting window focusing.