Feature request: Please add support for NTSync

[ExecThTs]

Currently XIVLauncher only has options for enabling ESync and FSync.
My kernel has support for NTSync:

[exec@falzar:~]$ uname -a
Linux falzar 6.17.6-arch1-1 #1 SMP PREEMPT_DYNAMIC Wed, 29 Oct 2025 22:23:47 +0000 x86_64 GNU/Linux
[exec@falzar:~]$ sudo modprobe ntsync
[exec@falzar:~]$ ls -lah /dev/ntsync
crw-rw-rw- 1 root root 10, 260 Nov  3 21:30 /dev/ntsync

XIVLauncher version is v1.2.1(43ed53b) installed via Flatpak, running on Arch Linux.

I also set up XIVLauncher to use Proton-GE installed via the asdf version manager method with setting its Wine path to Proton-GE's bin path.

It seems that XIVLauncher is doing something that's actively preventing to use NTSync even with kernel and Proton-GE support despite me trying out environment variables (like PROTON_USE_NTSYNC=1 %command% to launch the game with.
Part of normal (with FSync enabled) startup log:

Nov 04 00:36:15 falzar flatpak[31169]: fsync: up and running.
Nov 04 00:36:16 falzar flatpak[31235]: MESA-INTEL: warning: Haswell Vulkan support is incomplete
Nov 04 00:36:16 falzar flatpak[31235]: MESA-INTEL: warning: Haswell Vulkan support is incomplete
Nov 04 00:36:16 falzar flatpak[30996]: [00:36:16 INF] -------------------------------------------------------------------->
Nov 04 00:36:16 falzar flatpak[30996]: [00:36:16 INF] Dalamud.Injector, (c) 2023 XIVLauncher Contributors
Nov 04 00:36:16 falzar flatpak[30996]: [00:36:16 INF] Using start info: {"LoadMethod":0,"WorkingDirectory":"Z:\home\exec>
Nov 04 00:36:18 falzar flatpak[30996]: {"pid": 500, "handle": 0}
Nov 04 00:36:18 falzar flatpak[30996]: info: Game: ffxiv_dx11.exe
Nov 04 00:36:18 falzar flatpak[30996]: info: DXVK: v2.6.1-1-gplasync
Nov 04 00:36:18 falzar flatpak[30996]: info: Build: x86_64 gcc 14.2.0
Nov 04 00:36:18 falzar flatpak[30996]: info: Found built-in config:
Nov 04 00:36:18 falzar flatpak[30996]: info: d3d11.cachedDynamicResources = vi
Nov 04 00:36:18 falzar flatpak[30996]: info: Effective configuration:
Nov 04 00:36:18 falzar flatpak[30996]: info: d3d11.cachedDynamicResources = vi
Nov 04 00:36:18 falzar flatpak[30996]: info: Vulkan: Found vkGetInstanceProcAddr in winevulkan.dll @ 0x6ffffc77e430

Startup log with ESync,FSync not enabled in the launcher:

Nov 04 00:40:39 falzar flatpak[31846]: wineserver: using server-side synchronization.
Nov 04 00:40:40 falzar flatpak[31908]: MESA-INTEL: warning: Haswell Vulkan support is incomplete
Nov 04 00:40:40 falzar flatpak[31908]: MESA-INTEL: warning: Haswell Vulkan support is incomplete
Nov 04 00:40:40 falzar flatpak[31797]: [00:40:40 INF] -------------------------------------------------------------------->
Nov 04 00:40:40 falzar flatpak[31797]: [00:40:40 INF] Dalamud.Injector, (c) 2023 XIVLauncher Contributors
Nov 04 00:40:40 falzar flatpak[31797]: [00:40:40 INF] Using start info: {"LoadMethod":0,"WorkingDirectory":"Z:\home\exec>
Nov 04 00:40:43 falzar flatpak[31797]: info: Game: ffxiv_dx11.exe
Nov 04 00:40:43 falzar flatpak[31797]: info: DXVK: v2.6.1-1-gplasync
Nov 04 00:40:43 falzar flatpak[31797]: info: Build: x86_64 gcc 14.2.0
Nov 04 00:40:43 falzar flatpak[31797]: info: Found built-in config:
Nov 04 00:40:43 falzar flatpak[31797]: info: d3d11.cachedDynamicResources = vi
Nov 04 00:40:43 falzar flatpak[31797]: info: Effective configuration:
Nov 04 00:40:43 falzar flatpak[31797]: info: d3d11.cachedDynamicResources = vi
Nov 04 00:40:43 falzar flatpak[31797]: info: Vulkan: Found vkGetInstanceProcAddr in winevulkan.dll @ 0x6ffffc8ee430

If NTSync was in use then the line in bold should read wineserver: NTSync up and running!.

[rankynbass]

If you use proton wine directly like this (which you really shouldn't), you need to just add WINENTSYNC=1. If you want a version of wine with ntsync that is designed for use with XIVLauncher, use one of these: https://github.com/rankynbass/unofficial-wine-xiv-git/releases. The "ntsync" builds do not require any environment variable at all, they just automatically use ntsync. Except for the ValveBE 10-2 and 10-3 releases, which also require WINENTSYNC=1, since they are based on proton wine.