3 ms·

I don't think that's true on modern platforms where the compositor (Mutter in the case of Gnome) is always responsible for presenting the frame. Gamescope's di

I don't think that's true on modern platforms where the compositor (Mutter in the case of Gnome) is always responsible for presenting the frame. Gamescope's direct scanout bypasses this.

dijit 2y ago
I’ll look into it, but it used to be a choice in the game settings that bypassed the drawing display server entirely, and caused that full screen flicker you might recall when tabbing back to your desktop (and the switchover of rendering control, and subsequent huge performance loss of the running game). I wasn’t aware that this changed, but you could be right. Its definitely the same on Windows as it always was, which is the platform I most developed games for.
- zokier 2y ago
  > Its definitely the same on Windows as it always was, which is the platform I most developed games for. Not really. Most games use "borderless windowed" mode instead of fullscreen exclusive, and even FSE is not true exclusive mode anymore in most cases. https://devblogs.microsoft.com/directx/demystifying-full-screen-optimizations/ https://devblogs.microsoft.com/directx/demystifying-full-scr... > When using Fullscreen Optimizations, your game believes that it is running in Fullscreen Exclusive, but behind the scenes, Windows has the game running in borderless windowed mode. When a game is run in borderless windowed mode, the game does not have full control of the display– that overarching control is given back to the Desktop Window Manager (DWM). see also https://learn.microsoft.com/en-us/windows/win32/direct3ddxgi/for-best-performance--use-dxgi-flip-model https://learn.microsoft.com/en-us/windows/win32/direct3ddxgi...
  - ChocolateGod 2y ago
    I think Windows now also supports hardware overlays, so games running in fullscreen Windows can skip the compositor, which reduces the latency in no longer allowing games to directly write to the FB.
    - ack_complete 2y ago
      The DWM can do this even for windowed applications if they use flip model -- it will dynamically transition individual windows between compositing and independent flip (overlay).
- BearOso 2y ago
  Most compositors can do direct scanout when they detect a full screen surface. (This is broken right now with Gnome on X11 because of the way window frames are drawn: https://gitlab.gnome.org/GNOME/mutter/-/issues/2794 https://gitlab.gnome.org/GNOME/mutter/-/issues/2794 ) If the game uses the platform cursor then that will reflect the additional latency, but the actual input signals won't be delayed.
- hackernudes 2y ago
  Doesn't really work like that in Wayland. If an application framebuffer is full screen and in a compatible pixel format the compositor can do "direct scan out" where the compositor sends the framebuffer directly to the crtc instead of compositing first. I know that wlroots supports that. I'm not sure how much performance it saves to be honest. And I'll second that most commercial games do go through XWayland, though it depends on what games you like!
gf000 2y ago
https://wayland.app/protocols/fullscreen-shell-unstable-v1 https://wayland.app/protocols/fullscreen-shell-unstable-v1

I don't think that's true on modern platforms where the compositor (Mutter in the case of Gnome) is always responsible for presenting the frame. Gamescope's direct scanout bypasses this.

dijit 2y ago

I’ll look into it, but it used to be a choice in the game settings that bypassed the drawing display server entirely, and caused that full screen flicker you might recall when tabbing back to your desktop (and the switchover of rendering control, and subsequent huge performance loss of the running game). I wasn’t aware that this changed, but you could be right. Its definitely the same on Windows as it always was, which is the platform I most developed games for.

zokier 2y ago
> Its definitely the same on Windows as it always was, which is the platform I most developed games for. Not really. Most games use "borderless windowed" mode instead of fullscreen exclusive, and even FSE is not true exclusive mode anymore in most cases. https://devblogs.microsoft.com/directx/demystifying-full-screen-optimizations/ https://devblogs.microsoft.com/directx/demystifying-full-scr... > When using Fullscreen Optimizations, your game believes that it is running in Fullscreen Exclusive, but behind the scenes, Windows has the game running in borderless windowed mode. When a game is run in borderless windowed mode, the game does not have full control of the display– that overarching control is given back to the Desktop Window Manager (DWM). see also https://learn.microsoft.com/en-us/windows/win32/direct3ddxgi/for-best-performance--use-dxgi-flip-model https://learn.microsoft.com/en-us/windows/win32/direct3ddxgi...
- ChocolateGod 2y ago
  I think Windows now also supports hardware overlays, so games running in fullscreen Windows can skip the compositor, which reduces the latency in no longer allowing games to directly write to the FB.
  - ack_complete 2y ago
    The DWM can do this even for windowed applications if they use flip model -- it will dynamically transition individual windows between compositing and independent flip (overlay).
BearOso 2y ago
Most compositors can do direct scanout when they detect a full screen surface. (This is broken right now with Gnome on X11 because of the way window frames are drawn: https://gitlab.gnome.org/GNOME/mutter/-/issues/2794 https://gitlab.gnome.org/GNOME/mutter/-/issues/2794 ) If the game uses the platform cursor then that will reflect the additional latency, but the actual input signals won't be delayed.
hackernudes 2y ago
Doesn't really work like that in Wayland. If an application framebuffer is full screen and in a compatible pixel format the compositor can do "direct scan out" where the compositor sends the framebuffer directly to the crtc instead of compositing first. I know that wlroots supports that. I'm not sure how much performance it saves to be honest. And I'll second that most commercial games do go through XWayland, though it depends on what games you like!

gf000 2y ago

https://wayland.app/protocols/fullscreen-shell-unstable-v1 https://wayland.app/protocols/fullscreen-shell-unstable-v1