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

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