Initial basic version of this feature.

CURA-3335

cura_app.py

@@ -2,11 +2,14 @@
 
 # Copyright (c) 2015 Ultimaker B.V.
 # Cura is released under the terms of the AGPLv3 or higher.
-
+import argparse
+import json
 import os
 import sys
 import platform
+import time
 
+from PyQt5.QtNetwork import QLocalSocket
 from UM.Platform import Platform
 
 #WORKAROUND: GITHUB-88 GITHUB-385 GITHUB-612
@@ -58,5 +61,36 @@ if Platform.isWindows() and hasattr(sys, "frozen"):
 # Force an instance of CuraContainerRegistry to be created and reused later.
 cura.Settings.CuraContainerRegistry.getInstance()
 
+# Peek the arguments and look for the 'single-instance' flag.
+parser = argparse.ArgumentParser(prog="cura")  # pylint: disable=bad-whitespace
+cura.CuraApplication.CuraApplication.addCommandLineOptions(parser)
+parsed_command_line = vars(parser.parse_args())
+
+if "single_instance" in parsed_command_line and parsed_command_line["single_instance"]:
+    print("Check for single instance")
+    single_instance_socket = QLocalSocket()
+    single_instance_socket.connectToServer("ultimaker-cura")
+    single_instance_socket.waitForConnected()
+    if single_instance_socket.state() == QLocalSocket.ConnectedState:
+        print("Connected to the other Cura instance.")
+        print(repr(parsed_command_line))
+
+        payload = {"command": "clear-all"}
+        single_instance_socket.write(bytes(json.dumps(payload) + "\n", encoding="ASCII"))
+
+        payload = {"command": "focus"}
+        single_instance_socket.write(bytes(json.dumps(payload) + "\n", encoding="ASCII"))
+
+        if len(parsed_command_line["file"]) != 0:
+            for filename in parsed_command_line["file"]:
+                payload = { "command": "open", "filePath": filename }
+                single_instance_socket.write(bytes(json.dumps(payload) + "\n", encoding="ASCII"))
+
+        single_instance_socket.flush()
+
+
+        single_instance_socket.close()
+        sys.exit(0)
+
 app = cura.CuraApplication.CuraApplication.getInstance()
 app.run()