Windows 10 Fullscreen Optimisations is... weird

[SeeNoWeevil]

Doing a bit of experimentation with a selection of games set to Fullscreen Exclusive it seems like there are multiple types;

1. Games that fully run in FSO mode. Alt-tabbing is fast like borderless, overlays work etc.

2. Games that appear to run Fullscreen Exclusive and then quickly switch to FSO when the user brings up an overlay or alt-tabs. You can see the screen flash as it switches. Some of these games will actually *stay* in FSO mode permanently after alt-tabbing. For example, I run Snowrunner at 1440p Fullscreen on a screen with a 2160p native. The game will boot in FSE mode sending 1440p to my display. If I alt-tab the game will jump to FSO mode and start sending a scaled 2160p (i.e my desktop res). It will then stay that way.

3. Games that run Fullscreen Exclusive and don't use FSO at all. These actually seem quite rare (I think you might be able to force these into FSO by using Reshade). Overlays don't work or send you back to the desktop. Alt-tabbing is slow and unreliable.

I'm curious what exactly determines which mode is used. Maybe it's related to DX version? I'm curious if there will be further Windows updates that will move all types over to FSO.

[ko4]

It's game dependent
If you've got a second monitor, you can use this tool to see what mode its running on https://github.com/GameTechDev/PresentM ... tag/v1.5.2
You can disable FSO in the .exe properties-> compatability
I forgot but I think Apex legends behaves like #2, disabling FSO in properties also doesn't work
For games like Apex where the disable fullscreen optimization setting doesnt work you can disable FSO system wide via a registry tweak
[HKEY_CURRENT_USER\System\GameConfigStore]
change GameDVR_DXGIHonorFSEWindowsCompatible from 0 to 1