feat(input): implement multiseat support and virtual device naming (#4954)

docs/troubleshooting.md

@@ -159,6 +159,33 @@ If the input is still not working, you may need to add your user to the `input`
 sudo usermod -aG input $USER
 ```
 
+#### Multiseat
+
+If you run multiple concurrent Wayland sessions on separate logind seats (e.g. `seat0`, `seat1`),
+your compositor may ignore injected input unless Sunshine's virtual devices are assigned to the correct seat.
+
+Sunshine determines its target seat from `XDG_SEAT`, which is typically set automatically by your display manager.
+If needed, you can override it manually in your systemd service file or shell environment before starting Sunshine.
+
+When the seat is not `seat0`, Sunshine appends the seat name to its virtual device names, for example:
+
+- Keyboard passthrough (seat1)
+- Sunshine PS5 (virtual) pad (seat1)
+
+Sunshine creates two mouse devices: a relative one and an absolute one.
+
+To assign Sunshine's virtual devices to the correct seat, create this udev rules file
+(/etc/udev/rules.d/72-sunshine-virtual-seat.rules):
+```udev
+SUBSYSTEM=="input", KERNEL=="input*", ATTR{name}=="*(seat1)*", TAG+="seat", ENV{ID_SEAT}="seat1"
+```
+
+Then reload udev:
+
+```bash
+sudo udevadm control --reload-rules && sudo udevadm trigger -s input
+```
+
 ### KMS Streaming fails
 KMS screencasting requires elevated privileges which are not allowed for Flatpak or AppImage packages.
 This means that you must install Sunshine using the native package format of your distribution, if available.

src/platform/linux/input/inputtino_common.h

@@ -13,12 +13,28 @@
 #include "src/config.h"
 #include "src/logging.h"
 #include "src/platform/common.h"
+#include "src/platform/linux/input/inputtino_seat.h"
 #include "src/utility.h"
 
 using namespace std::literals;
 
 namespace platf {
 
+  inline std::string inputtino_name_for_seat(std::string_view base_name) {
+    auto seat_id = inputtino_seat::get_target_seat();
+    if (seat_id.empty() || seat_id == "seat0") {
+      return std::string(base_name);
+    }
+
+    std::string name;
+    name.reserve(base_name.size() + seat_id.size() + 3);
+    name.append(base_name);
+    name.append(" (");
+    name.append(seat_id);
+    name.push_back(')');
+    return name;
+  }
+
   using joypads_t = std::variant<inputtino::XboxOneJoypad, inputtino::SwitchJoypad, inputtino::PS5Joypad>;
 
   struct joypad_state {
@@ -30,13 +46,13 @@ namespace platf {
   struct input_raw_t {
     input_raw_t():
         mouse(inputtino::Mouse::create({
-          .name = "Mouse passthrough",
+          .name = inputtino_name_for_seat("Mouse passthrough"sv),
           .vendor_id = 0xBEEF,
           .product_id = 0xDEAD,
           .version = 0x111,
         })),
         keyboard(inputtino::Keyboard::create({
-          .name = "Keyboard passthrough",
+          .name = inputtino_name_for_seat("Keyboard passthrough"sv),
           .vendor_id = 0xBEEF,
           .product_id = 0xDEAD,
           .version = 0x111,
@@ -66,13 +82,13 @@ namespace platf {
   struct client_input_raw_t: public client_input_t {
     client_input_raw_t(input_t &input):
         touch(inputtino::TouchScreen::create({
-          .name = "Touch passthrough",
+          .name = inputtino_name_for_seat("Touch passthrough"sv),
           .vendor_id = 0xBEEF,
           .product_id = 0xDEAD,
           .version = 0x111,
         })),
         pen(inputtino::PenTablet::create({
-          .name = "Pen passthrough",
+          .name = inputtino_name_for_seat("Pen passthrough"sv),
           .vendor_id = 0xBEEF,
           .product_id = 0xDEAD,
           .version = 0x111,

src/platform/linux/input/inputtino_gamepad.cpp

@@ -10,6 +10,7 @@
 // local includes
 #include "inputtino_common.h"
 #include "inputtino_gamepad.h"
+#include "inputtino_seat.h"
 #include "src/config.h"
 #include "src/logging.h"
 #include "src/platform/common.h"
@@ -27,7 +28,7 @@ namespace platf::gamepad {
   };
 
   auto create_xbox_one() {
-    return inputtino::XboxOneJoypad::create({.name = "Sunshine X-Box One (virtual) pad",
+    return inputtino::XboxOneJoypad::create({.name = inputtino_name_for_seat("Sunshine X-Box One (virtual) pad"sv),
                                              // https://github.com/torvalds/linux/blob/master/drivers/input/joystick/xpad.c#L147
                                              .vendor_id = 0x045E,
                                              .product_id = 0x02EA,
@@ -35,7 +36,7 @@ namespace platf::gamepad {
   }
 
   auto create_switch() {
-    return inputtino::SwitchJoypad::create({.name = "Sunshine Nintendo (virtual) pad",
+    return inputtino::SwitchJoypad::create({.name = inputtino_name_for_seat("Sunshine Nintendo (virtual) pad"sv),
                                             // https://github.com/torvalds/linux/blob/master/drivers/hid/hid-ids.h#L981
                                             .vendor_id = 0x057e,
                                             .product_id = 0x2009,
@@ -50,7 +51,7 @@ namespace platf::gamepad {
       device_mac = std::format("02:00:00:00:00:{:02x}", globalIndex);
     }
 
-    return inputtino::PS5Joypad::create({.name = "Sunshine PS5 (virtual) pad", .vendor_id = 0x054C, .product_id = 0x0CE6, .version = 0x8111, .device_phys = device_mac, .device_uniq = device_mac});
+    return inputtino::PS5Joypad::create({.name = inputtino_name_for_seat("Sunshine PS5 (virtual) pad"sv), .vendor_id = 0x054C, .product_id = 0x0CE6, .version = 0x8111, .device_phys = device_mac, .device_uniq = device_mac});
   }
 
   int alloc(input_raw_t *raw, const gamepad_id_t &id, const gamepad_arrival_t &metadata, feedback_queue_t feedback_queue) {

src/platform/linux/input/inputtino_seat.cpp

@@ -0,0 +1,23 @@
+/**
+ * @file src/platform/linux/input/inputtino_seat.cpp
+ * @brief Implementation for multi-seat naming (udev-only).
+ */
+// standard includes
+#include <cstdlib>
+
+// local includes
+#include "inputtino_seat.h"
+
+namespace platf::inputtino_seat {
+
+  std::string get_target_seat() {
+    if (const char *seat = std::getenv("XDG_SEAT")) {
+      if (seat[0] != '\0') {
+        return seat;
+      }
+    }
+
+    return {};
+  }
+
+}  // namespace platf::inputtino_seat

src/platform/linux/input/inputtino_seat.h

@@ -0,0 +1,17 @@
+/**
+ * @file src/platform/linux/input/inputtino_seat.h
+ * @brief Helpers for multi-seat naming (udev-only).
+ */
+#pragma once
+
+#include <string>
+
+namespace platf::inputtino_seat {
+
+  /**
+   * Determine the target seat for the current Sunshine instance.
+   * Returns empty string if no seat could be determined.
+   */
+  std::string get_target_seat();
+
+}  // namespace platf::inputtino_seat

src_assets/linux/misc/60-sunshine.rules

@@ -1,11 +1,12 @@
-# Allows Sunshine to acces /dev/uinput
+# Allows Sunshine to access /dev/uinput
 KERNEL=="uinput", SUBSYSTEM=="misc", OPTIONS+="static_node=uinput", GROUP="input", MODE="0660", TAG+="uaccess"
 
 # Allows Sunshine to access /dev/uhid
 KERNEL=="uhid", GROUP="input", MODE="0660", TAG+="uaccess"
 
 # Joypads
-KERNEL=="hidraw*", ATTRS{name}=="Sunshine PS5 (virtual) pad", GROUP="input", MODE="0660", TAG+="uaccess"
-SUBSYSTEMS=="input", ATTRS{name}=="Sunshine X-Box One (virtual) pad", GROUP="input", MODE="0660", TAG+="uaccess"
-SUBSYSTEMS=="input", ATTRS{name}=="Sunshine gamepad (virtual) motion sensors", GROUP="input", MODE="0660", TAG+="uaccess"
-SUBSYSTEMS=="input", ATTRS{name}=="Sunshine Nintendo (virtual) pad", GROUP="input", MODE="0660", TAG+="uaccess"
+KERNEL=="hidraw*", ATTRS{name}=="Sunshine PS5 (virtual) pad*", GROUP="input", MODE="0660", TAG+="uaccess"
+SUBSYSTEMS=="input", ATTRS{name}=="Sunshine X-Box One (virtual) pad*", GROUP="input", MODE="0660", TAG+="uaccess"
+SUBSYSTEMS=="input", ATTRS{name}=="Sunshine gamepad (virtual) motion sensors*", GROUP="input", MODE="0660", TAG+="uaccess"
+SUBSYSTEMS=="input", ATTRS{name}=="Sunshine Nintendo (virtual) pad*", GROUP="input", MODE="0660", TAG+="uaccess"
+SUBSYSTEMS=="input", ATTRS{name}=="Sunshine PS5 (virtual) pad*", GROUP="input", MODE="0660", TAG+="uaccess"