Fullscreen set by DefaultGameUserSettings.ini no longer working

In UE 4.15, the packaged build will start in fullscreen mode by providing a DefaultGameUserSettings.ini with the following content:

[/Script/Engine.GameUserSettings]
bUseVSync=False
//ResolutionSizeX=1920
//ResolutionSizeY=1080
//LastUserConfirmedResolutionSizeX=1920
//LastUserConfirmedResolutionSizeY=1080
WindowPosX=-1
WindowPosY=-1
bUseDesktopResolutionForFullscreen=True
FullscreenMode=0
LastConfirmedFullscreenMode=0
Version=5

However, in UE 4.16.1 this is broken (regression). I have tried this on 3 different systems with each having the latest graphics driver (AMD and NVIDIA). It works for the first start of the packaged game only, afterwards the screen will go blank for a short time, and then the game will appear minimized. If I try to actived the minimized game, it will minimize again. I’ve tried again with UE 4.15, and it works fine again.

Edit 2017/06/26: This can only be reproduced while the classic Skype client is running and a call is active, see comments below.

I’m not in a position test this myself as I’m on 4.15 right now. However when having problems with exactly this file in the past I’ve turned off Pak files (File | Package Project | Packaging Settings → Packaging | User Pak File); this allows you to see the a) actual packaged DefaultGameUserSettings.ini file and b) the resultant GameUserSettings.ini file after the game has started and reserialised its configuration to disk.

If you do this it might allow you to apply a more “scientific” analysis of what’s going wrong; you’ll be able to diff the two files to see what changed after first startup - and possibly result in a more accurate bug report if an engine problem needs to be remediated. I’d be interested to know your findings if you do this…

Thank you for your feedback. This encouraged me to further analyse the matter - and it is a really strange bug.

  1. The DefaultGameUserSettings.ini file is correctly packaged.
  2. The resultant GameUserSettings.ini file is empty (contains only a linefeed, 2 bytes).

But then I found out, that this bug can only be reproduced while the (classic) Skype client is running and a call is active. When I asked other persons to test this on their PC (using different graphics card and OS) I called them via Skype so they also had Skype running during the test. This can be reproduced also by calling the Skype Echo / Sound Test Service and starting the game during the call.

I’ve had this bug reproduced on a total number of 8 PCs now while running the Skype client with an active call.

This remains a bug imo, because it should be possible to run Skype while starting the game in fullscreen mode.

This issue persists with the latest release of Skype (for Windows desktop). Is it really by design that you should not be allowed to play an Unreal Engine game in fullscreen mode while running a Skype call?