Window reduces when another window is active on Windows if Minecraft is in full screen.
Current behaviour :
Minecraft window reduces and takes time to reopen correctly.
Expected behaviour :
Minecraft window should not reduces and only set to inactive.
Is this still an issue in the most recent versions (currently that is 1.13.2, or the latest snapshot 18w49a) of Minecraft? If so, please update the affected versions and help us keeping this ticket updated from time to time. If you are the owner/reporter of this ticket, you can modify the affected version(s) yourself.