Why borderless fullscreen requires Vsync to prevent screentearing?

99939 · 09-22-2018, 05:56 AM #1

When playing a game in Dolphin in borderless fullscreen the screen tears. Windows uses compositing for all windows (including borderless) and tearing doesn't occur. Why there's screen tearing in Dolphin?

DaRkL3AD3R · 09-28-2018, 06:09 PM #2

If you are on the latest versions of Windows 10, there was a change to the way fullscreen gaming works. Now, exclusive fullscreen is not truly fullscreen and likewise borderless windowed is no longer always purely running under the desktop compositor.

Now there is something called "fullscreen optimizations" which automatically makes most Direct3D games play in a fake borderless fullscreen mode which is technically still rendered within the desktop compositor but disables the enforced vsync of running within the DWM.

For people who want the benefit of faster alt tabbing and running media on other screens, but don't want DWM vsync applying to their games causing increased input lag, this is very nice. For people who just want a way to force old school triple buffered vsync via the DWM, it's bad. It now means you have to either tell the application within its own software to run in regular borderless windowed and disable the FSO, or you're basically SOL.

Unfortunately even the people like myself who were perfectly happy with the limitations and benefits of true exclusive fullscreen, basically are screwed and have no proper fallback to the old fashioned way of rendering to the display. It is pretty much always running under the DWM no matter what you do and it interferes tremendously with things like gsync and vsync.

TLDR - install Windows 7 and be happy.

**DJBarry004** · 09-28-2018, 11:18 PM #3

Yeah, except 7´s extended support is about to end.

**mbc07** · 09-29-2018, 01:44 AM #4

... and that Microsoft currently denies download and installation of security updates if you're using Windows 7 with a Intel Kaby Lake or newer and AMD Ryzen or newer CPUs, leaving your system vulnerable to known security exploits.

**DJBarry004** · 09-29-2018, 08:07 AM #5

(09-29-2018, 01:44 AM)mbc07 Wrote: ... and that Microsoft currently denies download and installation of security updates if you're using Windows 7 with a Intel Kaby Lake or newer and AMD Ryzen or newer CPUs, leaving your system vulnerable to known security exploits.

Wow. I had no idea that Microsoft was so desperate to leave Windows 7 behind.

**Helios** · 09-29-2018, 08:50 AM #6

Microsoft is trying very very hard to avoid another Windows XP

Shadorino · 10-08-2018, 02:19 AM #7

DaRkL3AD3R has explained everything.
But to summarize, if you want the triple buffered V-Sync that comes with DWM like before: right click on Dolphin's exe > Compatibility tab > Disable fullscreen optimizations

**Helios** · 10-08-2018, 02:53 AM #8

I had zero idea that option existed.

Incredible.

Tayyo · 10-12-2018, 04:59 AM #9

Latest NVidia drivers broke the vsync-less borderless on my 980. May be it's Windows 1809, I don't know.

I'm having some problems with my old games through steam inhome streaming because of that.

Shadorino · (This post was last modified: 10-12-2018, 07:08 AM by Shadorino.)

I don't know if it's Windows 10 1809 that broke it for me too, since I have a G-Sync monitor I never have these issues. But I can confirm that regardless of the "Fullscreen Optimizations" option in the Dolphin exe, the DWM V-Sync is still forced on in borderless windowed mode with G-Sync and V-Sync disabled in the NVIDIA Control Panel.
Microsoft changed things again apparently... I haven't tested with any other games though.