Function steam_web_helper 

pub fn steam_web_helper() -> Rule

An in-process GPU, DXMT and no Metal HUD for Steam’s web helper.

Steam’s embedded browser (CEF): its GPU process cannot paint into the browser’s window (blank UI), so keep the GPU in-process. GPU rendering stays on and goes through DXMT, which the Steam client runs well on; the dxgi pin keeps it there over the * rules, built-in or from WINE_COMPATDB, while a WINE_COMPATDB rule for the helper that selects another tree moves it.

The Metal HUD is off, through metal_hud=false and the env entry MTL_HUD_ENABLED=0, for the same reason and in the same way as on the Social Club helper (social_club_helper); steam.exe, which starts the games, has no rule.