This is likely very significant news for anyone running Linux, especially if they want to game on a distribution of the open-source operating system. Valve has announced Proton, a derivative of Wine that will allow the Linux version of the Steam client to run some Windows games. In theory this could support a great many games, but as this feature is only in beta, Valve has a whitelist of supported games, which you can see at the source link. It is possible to disable the whitelist from within the beta Steam client though, for those wanting to take a chance.
Some of you may be wondering how Valve has achieved this, especially as DirectX is limited to the Windows operating system. Wine is a compatibility layer that succeeds in getting many Windows applications to run on other operating systems by translating Windows API calls to POSIX calls these other OSes can understand. Proton, being based on Wine, will be similar in behavior, and Valve has been working on improving Wine for some time. To address Direct3D calls, DXVK is used, which is a translation layer that similarly translates the DirectX API calls to Vulkan, which can run on other operating systems, including Linux. (It can also run on Windows and I have seen some people try it, to get DX11 games running in Vulkan.) For DX12 API calls, VKD3D is used to translate the calls to work with Vulkan.
As this is currently in beta, we will not see the currently whitelisted games marked, as part of Steam Play, as support Linux. Additionally, if you try it out and run into problems, if they are Linux-specific, you will be directed to Steam for support. However, Valve is only whitelisting games it has tested and found the experience to be identical, except for a change in performance. For anyone wondering about macOS support, there are currently no plans to bring this functionality there, even though Wine and Proton can both work on the operating system.
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