Add the ability to get per-platform information for joypads.

This adds the ability for games to obtain platform-specific information about joypads such as their vendor/product ID, their XInput gamepad index or the real name of the device before it gets swapped out by the gamecontrollerdb's name.

This PR also includes a rebased version of #76045, this is because this PR is intended to be mainly to help people implementing Steam Input, as having the gamepad index is essential.

core/input/input.cpp

@@ -113,6 +113,7 @@ void Input::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_joy_axis", "device", "axis"), &Input::get_joy_axis);
 	ClassDB::bind_method(D_METHOD("get_joy_name", "device"), &Input::get_joy_name);
 	ClassDB::bind_method(D_METHOD("get_joy_guid", "device"), &Input::get_joy_guid);
+	ClassDB::bind_method(D_METHOD("get_joy_info", "device"), &Input::get_joy_info);
 	ClassDB::bind_method(D_METHOD("should_ignore_device", "vendor_id", "product_id"), &Input::should_ignore_device);
 	ClassDB::bind_method(D_METHOD("get_connected_joypads"), &Input::get_connected_joypads);
 	ClassDB::bind_method(D_METHOD("get_joy_vibration_strength", "device"), &Input::get_joy_vibration_strength);
@@ -437,11 +438,12 @@ static String _hex_str(uint8_t p_byte) {
 	return ret;
 }
 
-void Input::joy_connection_changed(int p_idx, bool p_connected, String p_name, String p_guid) {
+void Input::joy_connection_changed(int p_idx, bool p_connected, String p_name, String p_guid, Dictionary p_joypad_info) {
 	_THREAD_SAFE_METHOD_
 	Joypad js;
 	js.name = p_connected ? p_name : "";
 	js.uid = p_connected ? p_guid : "";
+	js.info = p_connected ? p_joypad_info : Dictionary();
 
 	if (p_connected) {
 		String uidname = p_guid;
@@ -1499,6 +1501,11 @@ String Input::get_joy_guid(int p_device) const {
 	return joy_names[p_device].uid;
 }
 
+Dictionary Input::get_joy_info(int p_device) const {
+	ERR_FAIL_COND_V(!joy_names.has(p_device), Dictionary());
+	return joy_names[p_device].info;
+}
+
 bool Input::should_ignore_device(int p_vendor_id, int p_product_id) const {
 	uint32_t full_id = (((uint32_t)p_vendor_id) << 16) | ((uint16_t)p_product_id);
 	return ignored_device_ids.has(full_id);

core/input/input.h

@@ -149,6 +149,7 @@ private:
 		HatMask last_hat = HatMask::CENTER;
 		int mapping = -1;
 		int hat_current = 0;
+		Dictionary info;
 	};
 
 	VelocityTrack mouse_velocity_track;
@@ -276,7 +277,7 @@ public:
 	Vector2 get_joy_vibration_strength(int p_device);
 	float get_joy_vibration_duration(int p_device);
 	uint64_t get_joy_vibration_timestamp(int p_device);
-	void joy_connection_changed(int p_idx, bool p_connected, String p_name, String p_guid = "");
+	void joy_connection_changed(int p_idx, bool p_connected, String p_name, String p_guid = "", Dictionary p_joypad_info = Dictionary());
 
 	Vector3 get_gravity() const;
 	Vector3 get_accelerometer() const;
@@ -332,6 +333,7 @@ public:
 	bool is_joy_known(int p_device);
 	String get_joy_guid(int p_device) const;
 	bool should_ignore_device(int p_vendor_id, int p_product_id) const;
+	Dictionary get_joy_info(int p_device) const;
 	void set_fallback_mapping(String p_guid);
 
 	void flush_buffered_events();

doc/classes/Input.xml

@@ -121,6 +121,20 @@
 				Returns a SDL2-compatible device GUID on platforms that use gamepad remapping, e.g. [code]030000004c050000c405000000010000[/code]. Returns [code]"Default Gamepad"[/code] otherwise. Godot uses the [url=https://github.com/gabomdq/SDL_GameControllerDB]SDL2 game controller database[/url] to determine gamepad names and mappings based on this GUID.
 			</description>
 		</method>
+		<method name="get_joy_info" qualifiers="const">
+			<return type="Dictionary" />
+			<param index="0" name="device" type="int" />
+			<description>
+				Returns a dictionary with extra platform-specific information about the device, e.g. the raw gamepad name from the OS or the Steam Input index.
+				On Windows the dictionary contains the following fields:
+				[code]xinput_index[/code]: The index of the controller in the XInput system.
+				On Linux:
+				[code]raw_name[/code]: The name of the controller as it came from the OS, before getting renamed by the godot controller database.
+				[code]vendor_id[/code]: The USB vendor ID of the device.
+				[code]product_id[/code]: The USB product ID of the device.
+				[code]steam_input_index[/code]: The Steam Input gamepad index, if the device is not a Steam Input device this key won't be present.
+			</description>
+		</method>
 		<method name="get_joy_name">
 			<return type="String" />
 			<param index="0" name="device" type="int" />

platform/linuxbsd/joypad_linux.cpp

@@ -56,6 +56,14 @@
 static const char *ignore_str = "/dev/input/js";
 #endif
 
+// On Linux with Steam Input Xbox 360 devices have an index appended to their device name, this index is
+// the Steam Input gamepad index
+#define VALVE_GAMEPAD_NAME_PREFIX "Microsoft X-Box 360 pad "
+// IDs used by Steam Input virtual controllers.
+// See https://partner.steamgames.com/doc/features/steam_controller/steam_input_gamepad_emulation_bestpractices
+#define VALVE_GAMEPAD_VID 0x28DE
+#define VALVE_GAMEPAD_PID 0x11FF
+
 JoypadLinux::Joypad::~Joypad() {
 	for (int i = 0; i < MAX_ABS; i++) {
 		if (abs_info[i]) {
@@ -411,8 +419,23 @@ void JoypadLinux::open_joypad(const char *p_path) {
 		setup_joypad_properties(joypad);
 		sprintf(uid, "%04x%04x", BSWAP16(inpid.bustype), 0);
 		if (inpid.vendor && inpid.product && inpid.version) {
+			Dictionary joypad_info;
+			joypad_info["vendor_id"] = inpid.vendor;
+			joypad_info["product_id"] = inpid.product;
+			joypad_info["raw_name"] = name;
+
 			sprintf(uid + String(uid).length(), "%04x%04x%04x%04x%04x%04x", vendor, 0, product, 0, version, 0);
-			input->joy_connection_changed(joy_num, true, name, uid);
+
+			if (inpid.vendor == VALVE_GAMEPAD_VID && inpid.product == VALVE_GAMEPAD_PID) {
+				if (name.begins_with(VALVE_GAMEPAD_NAME_PREFIX)) {
+					String idx_str = name.substr(strlen(VALVE_GAMEPAD_NAME_PREFIX));
+					if (idx_str.is_valid_int()) {
+						joypad_info["steam_input_index"] = idx_str.to_int();
+					}
+				}
+			}
+
+			input->joy_connection_changed(joy_num, true, name, uid, joypad_info);
 		} else {
 			String uidname = uid;
 			int uidlen = MIN(name.length(), 11);

platform/windows/joypad_windows.cpp

@@ -318,7 +318,9 @@ void JoypadWindows::probe_joypads() {
 				x_joypads[i].ff_end_timestamp = 0;
 				x_joypads[i].vibrating = false;
 				attached_joypads[id] = true;
-				input->joy_connection_changed(id, true, "XInput Gamepad", "__XINPUT_DEVICE__");
+				Dictionary joypad_info;
+				joypad_info["xinput_index"] = (int)i;
+				input->joy_connection_changed(id, true, "XInput Gamepad", "__XINPUT_DEVICE__", joypad_info);
 			}
 		} else if (x_joypads[i].attached) {
 			x_joypads[i].attached = false;