WIP: Make application initialization and start up more clear

- Create SingleInstance class to handling single instance stuff.
 - Instead of calling getInstance() everywhere, initialize each object
   explicitly in order when application starts and getInstance()s do not
   create instances any more and they merely return the created
   instances.
 - Only set initial values in construtor functions __init__(). Move the
   initialization of context-aware (i.e. things that depend on other
   things) to separate functions.
 - Split application creation and initialziation into several steps and
   them should be called explicitly in the correct order.

cura_app.py

@@ -1,51 +1,36 @@
 #!/usr/bin/env python3
 
-# Copyright (c) 2015 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
-import argparse
+import faulthandler
 import os
 import sys
 
 from UM.Platform import Platform
 
-parser = argparse.ArgumentParser(prog = "cura",
-                                 add_help = False)
-parser.add_argument('--debug',
-                    action='store_true',
-                    default = False,
-                    help = "Turn on the debug mode by setting this option."
-                    )
-parser.add_argument('--trigger-early-crash',
-                    dest = 'trigger_early_crash',
-                    action = 'store_true',
-                    default = False,
-                    help = "FOR TESTING ONLY. Trigger an early crash to show the crash dialog."
-                    )
-known_args = vars(parser.parse_known_args()[0])
 
-if not known_args["debug"]:
-    def get_cura_dir_path():
-        if Platform.isWindows():
-            return os.path.expanduser("~/AppData/Roaming/cura/")
-        elif Platform.isLinux():
-            return os.path.expanduser("~/.local/share/cura")
-        elif Platform.isOSX():
-            return os.path.expanduser("~/Library/Logs/cura")
+# Gets the directory for stdout and stderr
+def get_cura_dir_for_stdoutputs() -> str:
+    if Platform.isWindows():
+        return os.path.expanduser("~/AppData/Roaming/cura/")
+    elif Platform.isLinux():
+        return os.path.expanduser("~/.local/share/cura")
+    elif Platform.isOSX():
+        return os.path.expanduser("~/Library/Logs/cura")
 
-    if hasattr(sys, "frozen"):
-        dirpath = get_cura_dir_path()
-        os.makedirs(dirpath, exist_ok = True)
-        sys.stdout = open(os.path.join(dirpath, "stdout.log"), "w", encoding = "utf-8")
-        sys.stderr = open(os.path.join(dirpath, "stderr.log"), "w", encoding = "utf-8")
 
-import platform
-import faulthandler
+# Change stdout and stderr to files if Cura is running as a packaged application.
+if hasattr(sys, "frozen"):
+    dir_path = get_cura_dir_for_stdoutputs()
+    os.makedirs(dir_path, exist_ok = True)
+    sys.stdout = open(os.path.join(dir_path, "stdout.log"), "w", encoding = "utf-8")
+    sys.stderr = open(os.path.join(dir_path, "stderr.log"), "w", encoding = "utf-8")
 
-#WORKAROUND: GITHUB-88 GITHUB-385 GITHUB-612
+
+# WORKAROUND: GITHUB-88 GITHUB-385 GITHUB-612
 if Platform.isLinux(): # Needed for platform.linux_distribution, which is not available on Windows and OSX
     # For Ubuntu: https://bugs.launchpad.net/ubuntu/+source/python-qt4/+bug/941826
-    linux_distro_name = platform.linux_distribution()[0].lower()
     # The workaround is only needed on Ubuntu+NVidia drivers. Other drivers are not affected, but fine with this fix.
     try:
         import ctypes
@@ -79,6 +64,7 @@ if "PYTHONPATH" in os.environ.keys():                       # If PYTHONPATH is u
             sys.path.remove(PATH_real)
         sys.path.insert(1, PATH_real)                       # Insert it at 1 after os.curdir, which is 0.
 
+
 def exceptHook(hook_type, value, traceback):
     from cura.CrashHandler import CrashHandler
     from cura.CuraApplication import CuraApplication
@@ -121,25 +107,25 @@ def exceptHook(hook_type, value, traceback):
         _crash_handler.early_crash_dialog.show()
         sys.exit(application.exec_())
 
-if not known_args["debug"]:
-    sys.excepthook = exceptHook
+
+# Set exception hook to use the crash dialog handler
+sys.excepthook = exceptHook
+# Enable dumping traceback for all threads
+faulthandler.enable(all_threads = True)
 
 # Workaround for a race condition on certain systems where there
 # is a race condition between Arcus and PyQt. Importing Arcus
 # first seems to prevent Sip from going into a state where it
 # tries to create PyQt objects on a non-main thread.
 import Arcus #@UnusedImport
-import cura.CuraApplication
-import cura.Settings.CuraContainerRegistry
+from cura.CuraApplication import CuraApplication
 
-faulthandler.enable()
+app = CuraApplication()
+app.addCommandLineOptions()
+app.parseCliOptions()
+app.initialize()
 
-# Force an instance of CuraContainerRegistry to be created and reused later.
-cura.Settings.CuraContainerRegistry.CuraContainerRegistry.getInstance()
+app.startSlashWindowPhase()
+app.startPostSlashWindowPhase()
 
-# This pre-start up check is needed to determine if we should start the application at all.
-if not cura.CuraApplication.CuraApplication.preStartUp(parser = parser, parsed_command_line = known_args):
-    sys.exit(0)
-
-app = cura.CuraApplication.CuraApplication.getInstance(parser = parser, parsed_command_line = known_args)
 app.run()