Add boss key on windows

[adryzz]

• Closes Boss Key #6790
• Depends on Add notification tray icon on windows (boss key) osu-framework#6341

out1.mp4

Currently there's a small issue when hiding the window in fullscreen, bigger explaination in the framework-side PR.

[Feodor0090]

I can't understand approach with tray icon.

The key point of "boss key" is not to just hide window, there is a "-" button on header for that. Its purpose is to hide the fact that game is running. So you hide window's icon from main task panel area... and create another one in tray. So we still have a game icon, just in another place. Great.

Why not to modify code at https://github.com/ppy/osu/blob/master/osu.Desktop/Program.cs#L127 to not silently return, but to "ping" running game instance making it show&bring its window? So boss key will actually hide the game without any icons, and re-running exe will pick you up from where you left off.

[adryzz]

hide the fact that game is running

the point of the boss key is that if the boss comes over and looks at your screen, osu! is nowhere to be seen.

it isn't meant to protect you against someone actively searching for a game instance running.

[lizhanyiawa]

When will this pull request finally be included in game? Can't wait for it

[adryzz]

been kinda busy with university and exams and stuff, so getting this PR merged asap isnt my absolute priority.

when i have some free time i'll fix the conflicts and stuff

[lizhanyiawa]

yeah that is tough and hope you get good grades ❤️