LibGUI: Add KeyEvent::to_string()

This makes it way easier to debug key events.

Libraries/LibGUI/Event.cpp

@@ -24,6 +24,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <AK/StringBuilder.h>
+#include <Kernel/KeyCode.h>
 #include <LibCore/MimeData.h>
 #include <LibGUI/Event.h>
 
@@ -41,4 +43,31 @@ DropEvent::~DropEvent()
 {
 }
 
+String KeyEvent::to_string() const
+{
+    Vector<String, 8> parts;
+
+    if (m_modifiers & Mod_Ctrl)
+        parts.append("Ctrl");
+    if (m_modifiers & Mod_Shift)
+        parts.append("Shift");
+    if (m_modifiers & Mod_Alt)
+        parts.append("Alt");
+    if (m_modifiers & Mod_Logo)
+        parts.append("Logo");
+
+    if (auto* key_name = key_code_to_string(static_cast<KeyCode>(m_key)))
+        parts.append(key_name);
+    else
+        parts.append("(Invalid)");
+
+    StringBuilder builder;
+    for (size_t i = 0; i < parts.size(); ++i) {
+        builder.append(parts[i]);
+        if (i != parts.size() - 1)
+            builder.append('+');
+    }
+    return builder.to_string();
+}
+
 }

Libraries/LibGUI/Event.h

@@ -278,6 +278,8 @@ public:
     u8 modifiers() const { return m_modifiers; }
     String text() const { return m_text; }
 
+    String to_string() const;
+
 private:
     friend class WindowServerConnection;
     int m_key { 0 };