--- a/src/X11Handler.h	Thu Apr 01 21:19:50 2021 +0200
+++ b/src/X11Handler.h	Fri Apr 02 18:34:52 2021 +0200
@@ -40,6 +40,12 @@
 class X11Handler : public relpipe::reader::handlers::RelationalReaderStringHandler {
 private:
 
+	enum class RelationType {
+		UNSUPPORTED,
+		DEVICES,
+		EVENTS,
+	};
+
 	class Display {
 	public:
 		::Display* display = nullptr;
@@ -76,8 +82,17 @@
 		int y = -1;
 	} currentEvent;
 
+	class Device {
+	public:
+		relpipe::common::type::Integer id = -1;
+		relpipe::common::type::StringX name;
+		relpipe::common::type::StringX type;
+	} currentDevice;
+
 	Display display;
 	Configuration& configuration;
+	RelationType relationType = RelationType::UNSUPPORTED;
+	relpipe::common::type::StringX relationName;
 	std::vector<relpipe::reader::handlers::AttributeMetadata> attributes;
 	relpipe::common::type::Integer attributeIndex = 0;
 public:
@@ -87,20 +102,49 @@
 	}
 
 	void startRelation(relpipe::common::type::StringX name, std::vector<relpipe::reader::handlers::AttributeMetadata> attributes) override {
-		// TODO: check relation name, print waring if it does not match
-		if (display.display) {
-			if (this->attributes.empty()) {
-				this->attributes = attributes;
-			} else {
-				throw std::logic_error("Only a single relation can be converted to the X11 format.");
-			}
+		this->attributes = attributes;
+		this->relationName = name;
+
+		if (relationName == L"x11_input_device") {
+			this->relationType = RelationType::DEVICES;
+		} else if (relationName == L"x11_input_event") {
+			this->relationType = RelationType::EVENTS;
+			if (display.display == nullptr) throw std::invalid_argument("Unable to open display. Please check the $DISPLAY variable.");
 		} else {
-			throw std::invalid_argument("Unable to open display. Please check the $DISPLAY variable.");
+			this->relationType = RelationType::UNSUPPORTED;
+			std::wcerr << L"Unsupported relation: " << relationName << std::endl;
+			// TODO: throw exception?
 		}
-
 	}
 
 	void attribute(const relpipe::common::type::StringX& value) override {
+		if (relationType == RelationType::DEVICES) attributeOfDevice(value);
+		else if (relationType == RelationType::EVENTS) attributeOfEvent(value);
+		else attributeOfUnsupported(value);
+	}
+
+private:
+
+	void attributeOfDevice(const relpipe::common::type::StringX& value) {
+		if (attributes[attributeIndex].getAttributeName() == L"id") currentDevice.id = stol(value);
+		else if (attributes[attributeIndex].getAttributeName() == L"name") currentDevice.name = value;
+		else if (attributes[attributeIndex].getAttributeName() == L"type") currentDevice.type = value;
+		// else: ignore other attributes
+
+		attributeIndex++;
+
+		if (attributeIndex % attributes.size() == 0) {
+			if (configuration.debug) std::wcerr << L"Device: id = „" << currentDevice.id << L"“ name = „" << currentDevice.name << L"“ type = „" << currentDevice.type << L"“" << std::endl;
+			attributeIndex = 0;
+			currentEvent = Event();
+		}
+	}
+
+	void attributeOfUnsupported(const relpipe::common::type::StringX& value) {
+		if (configuration.debug) std::wcerr << L"Unsupported relation „" << relationName << L"“ has attribute „" << value << L"“" << std::endl;
+	}
+
+	void attributeOfEvent(const relpipe::common::type::StringX& value) {
 		// TODO: strictly expect correct data types (integers)?
 		// TODO: shorter codes (k/b/m, p/r) instead of names or both?
 		if (attributes[attributeIndex].getAttributeName() == L"device") {