feat(host/windows): ViGEm virtual gamepad backend

Windows GamepadManager via vigem-client (ViGEmBus) — the uinput-xpad analogue: one virtual Xbox 360 controller per client pad index, created lazily on first State. GameStream/Moonlight already uses the XInput conventions (low-16 button bits, sticks -32768..32767 +Y up, triggers 0..255), so the GamepadFrame->XGamepad mapping is 1:1. Replaces the non-Linux GamepadManager stub (same new/handle/pump_rumble API the m3 PadBackend drives, so no m3 change). Graceful when ViGEmBus is absent (gamepad disabled, session continues). Compiles clean on Windows + Linux; live-test needs the ViGEmBus driver + a physical pad. Rumble back-channel is a TODO (ViGEm notification API).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -2658,6 +2658,7 @@ dependencies = [
  "utoipa",
  "utoipa-axum",
  "utoipa-scalar",
+ "vigem-client",
  "wasapi",
  "wayland-backend",
  "wayland-client",
@@ -3967,6 +3968,15 @@ version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
+[[package]]
+name = "vigem-client"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b857e6f99efe1e1eb1e4dfb035de8ae7ec8ec56bd1928edcbd7c6e4427634d52"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "wait-timeout"
 version = "0.2.1"
@@ -4214,6 +4224,22 @@ dependencies = [
  "safe_arch",
 ]
 
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
 [[package]]
 name = "winapi-util"
 version = "0.1.11"
@@ -4223,6 +4249,12 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
+
 [[package]]
 name = "windows"
 version = "0.62.2"

crates/punktfunk-host/Cargo.toml

@@ -127,6 +127,8 @@ windows = { version = "0.62", features = [
 openh264 = "0.9"
 # WASAPI loopback audio capture (default render endpoint -> 48 kHz stereo f32 for the Opus path).
 wasapi = "0.23"
+# Virtual Xbox 360 gamepad via ViGEmBus (the uinput-xpad analogue) — driver installed separately.
+vigem-client = "0.1"
 # NVENC hardware encoder (NVENC SDK, D3D11 input). The SDK pins `cudarc` with
 # `cuda-version-from-build-system` (a build-time CUDA-toolkit probe); its `ci-check` feature switches
 # cudarc to `dynamic-loading` (loads nvcuda.dll at runtime — nothing needed at build), which is how

crates/punktfunk-host/src/inject.rs

@@ -298,8 +298,12 @@ fn gs_button_to_evdev(b: u32) -> Option<u32> {
 pub mod dualsense;
 #[cfg(target_os = "linux")]
 pub mod gamepad;
-/// Stub — virtual gamepads need Linux uinput; events are dropped elsewhere.
+/// Windows: virtual Xbox 360 pads via ViGEmBus.
-#[cfg(not(target_os = "linux"))]
+#[cfg(target_os = "windows")]
+#[path = "inject/gamepad_windows.rs"]
+pub mod gamepad;
+/// Stub — virtual gamepads need Linux uinput or Windows ViGEmBus; events are dropped elsewhere.
+#[cfg(not(any(target_os = "linux", target_os = "windows")))]
 pub mod gamepad {
     #[derive(Default)]
     pub struct GamepadManager;

crates/punktfunk-host/src/inject/gamepad_windows.rs

@@ -0,0 +1,70 @@
+//! Windows virtual gamepad via ViGEmBus — the analogue of the Linux uinput Xbox-360 pad.
+//! One virtual Xbox 360 controller per client pad index. GameStream/Moonlight already uses the
+//! XInput button/stick/trigger conventions (low 16 button bits, sticks −32768..32767 +Y up,
+//! triggers 0..255), so the mapping is ~1:1.
+//!
+//! Needs the ViGEmBus driver installed (like SudoVDA for the display); absent → gamepad is disabled
+//! and the session continues without it. Rumble back-channel: TODO (ViGEm notification API).
+
+use crate::gamestream::gamepad::GamepadEvent;
+use std::collections::HashMap;
+use std::sync::Arc;
+use vigem_client::{Client, TargetId, XButtons, XGamepad, Xbox360Wired};
+
+pub struct GamepadManager {
+    client: Option<Arc<Client>>,
+    pads: HashMap<u8, Xbox360Wired<Arc<Client>>>,
+}
+
+impl GamepadManager {
+    pub fn new() -> GamepadManager {
+        let client = match Client::connect() {
+            Ok(c) => {
+                tracing::info!("ViGEmBus connected (virtual Xbox 360 gamepads)");
+                Some(Arc::new(c))
+            }
+            Err(e) => {
+                tracing::warn!(
+                    error = format!("{e:?}"),
+                    "ViGEmBus unavailable — gamepad disabled (install ViGEmBus)"
+                );
+                None
+            }
+        };
+        GamepadManager {
+            client,
+            pads: HashMap::new(),
+        }
+    }
+
+    pub fn handle(&mut self, ev: &GamepadEvent) {
+        let Some(client) = self.client.clone() else {
+            return;
+        };
+        let GamepadEvent::State(f) = ev else {
+            return; // Arrival metadata — the pad is created lazily on the first State
+        };
+        let target = self.pads.entry(f.index.max(0) as u8).or_insert_with(|| {
+            let mut t = Xbox360Wired::new(client, TargetId::XBOX360_WIRED);
+            let _ = t.plugin();
+            let _ = t.wait_ready();
+            t
+        });
+        let gp = XGamepad {
+            buttons: XButtons {
+                raw: (f.buttons & 0xffff) as u16,
+            },
+            left_trigger: f.left_trigger,
+            right_trigger: f.right_trigger,
+            thumb_lx: f.ls_x,
+            thumb_ly: f.ls_y,
+            thumb_rx: f.rs_x,
+            thumb_ry: f.rs_y,
+        };
+        let _ = target.update(&gp);
+    }
+
+    pub fn pump_rumble(&mut self, _send: impl FnMut(u16, u16, u16)) {
+        // TODO: wire the ViGEm rumble notification back-channel (Xbox360Wired::request_notification).
+    }
+}