SDL: Don't filter out controllers when launched by Steam under Proton

SDL Commits
1 
From 3060105cfa8e67dc47936274c63580a7adb2736d Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Thu, 5 Dec 2024 19:22:32 -0800
Subject: [PATCH] Don't filter out controllers when launched by Steam under
 Proton

Fixes https://github.com/libsdl-org/SDL/issues/11579
---
 src/joystick/SDL_gamepad.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/joystick/SDL_gamepad.c b/src/joystick/SDL_gamepad.c
index 0ad193f5dc1f2..f967185bb37a7 100644
--- a/src/joystick/SDL_gamepad.c
+++ b/src/joystick/SDL_gamepad.c
@@ -2620,6 +2620,17 @@ bool SDL_ShouldIgnoreGamepad(Uint16 vendor_id, Uint16 product_id, Uint16 version
         return true;
     }
 
+#ifdef SDL_PLATFORM_WIN32
+    if (SDL_GetHintBoolean("SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD", false) &&
+        SDL_GetHintBoolean("STEAM_COMPAT_PROTON", false)) {
+        // We are launched by Steam and running under Proton
+        // We can't tell whether this controller is a Steam Virtual Gamepad,
+        // so assume that Proton is doing the appropriate filtering of controllers
+        // and anything we see here is fine to use.
+        return false;
+    }
+#endif // SDL_PLATFORM_WIN32
+
     if (SDL_IsJoystickSteamVirtualGamepad(vendor_id, product_id, version)) {
         return !SDL_GetHintBoolean("SDL_GAMECONTROLLER_ALLOW_STEAM_VIRTUAL_GAMEPAD", false);
     }