Adding PyQt5 compatibility (broken)

Adding compatibility for PyQt5 via a shim in Qt.py. This restructures the PyQt5 libraries
to match the layout seen in PyQt4, allowing it to continue to be used as drop in replacement.

This works up to the point of importing, however other API changes are broken - for example
the deprectation of .scale() on GraphicsItems throws an error currently.

pyqtgraph/Qt.py

@@ -11,25 +11,40 @@ This module exists to smooth out some of the differences between PySide and PyQt
 
 import sys, re
 
+PYSIDE = 0
+PYQT4 = 1
+PYQT5 = 2
+
+USE_QT_PY = None
+
 ## Automatically determine whether to use PyQt or PySide. 
 ## This is done by first checking to see whether one of the libraries
 ## is already imported. If not, then attempt to import PyQt4, then PySide.
 if 'PyQt4' in sys.modules:
-    USE_PYSIDE = False
+    USE_QT_PY = PYQT4
+if 'PyQt5' in sys.modules:
+    USE_QT_PY = PYQT5
 elif 'PySide' in sys.modules:
-    USE_PYSIDE = True
+    USE_QT_PY = PYSIDE
 else:
     try:
         import PyQt4
-        USE_PYSIDE = False
+        USE_QT_PY = PYQT4
+    except ImportError:
+        try:
+            import PyQt5
+            USE_QT_PY = PYQT5
         except ImportError:
             try:
                 import PySide
-            USE_PYSIDE = True
-        except ImportError:
-            raise Exception("PyQtGraph requires either PyQt4 or PySide; neither package could be imported.")
+                USE_QT_PY = PYSIDE
+            except:
+                pass
 
-if USE_PYSIDE:
+if USE_QT_PY == None:
+    raise Exception("PyQtGraph requires one of PyQt4, PyQt5 or PySide; none of these packages could be imported.")
+
+if USE_QT_PY == PYSIDE:
     from PySide import QtGui, QtCore, QtOpenGL, QtSvg
     import PySide
     VERSION_INFO = 'PySide ' + PySide.__version__
@@ -65,8 +80,8 @@ if USE_PYSIDE:
 
         return form_class, base_class
 
+elif USE_QT_PY == PYQT4:
 
-else:
     from PyQt4 import QtGui, QtCore, uic
     try:
         from PyQt4 import QtSvg
@@ -83,10 +98,36 @@ else:
     QtCore.Signal = QtCore.pyqtSignal
     VERSION_INFO = 'PyQt4 ' + QtCore.PYQT_VERSION_STR + ' Qt ' + QtCore.QT_VERSION_STR
 
+elif USE_QT_PY == PYQT5:
+    
+    # We're using PyQt5 which has a different structure so we're going to use a shim to
+    # recreate the Qt4 structure for Qt5
+    from PyQt5 import QtGui, QtCore, QtWidgets, Qt, uic
+    try:
+        from PyQt5 import QtSvg
+    except ImportError:
+        pass
+    try:
+        from PyQt5 import QtOpenGL
+    except ImportError:
+        pass
+    
+    QtGui.QApplication = QtWidgets.QApplication
+    QtGui.QGraphicsScene = QtWidgets.QGraphicsScene
+    QtGui.QGraphicsObject = QtWidgets.QGraphicsObject
+    QtGui.QGraphicsWidget = QGraphicsWidget5
+    QtGui.QApplication.setGraphicsSystem = None
+    QtCore.Signal = Qt.pyqtSignal
+    
+    # Import all QtWidgets objects into QtGui
+    for o in dir(QtWidgets):
+        if o.startswith('Q'):
+            setattr(QtGui, o, getattr(QtWidgets,o) )
     
 ## Make sure we have Qt >= 4.7
 versionReq = [4, 7]
-QtVersion = PySide.QtCore.__version__ if USE_PYSIDE else QtCore.QT_VERSION_STR
+USE_PYSIDE = USE_QT_PY == PYSIDE # still needed internally elsewhere
+QtVersion = PySide.QtCore.__version__ if USE_QT_PY ==  PYSIDE else QtCore.QT_VERSION_STR
 m = re.match(r'(\d+)\.(\d+).*', QtVersion)
 if m is not None and list(map(int, m.groups())) < versionReq:
     print(list(map(int, m.groups())))

pyqtgraph/__init__.py

@@ -41,6 +41,7 @@ elif 'darwin' in sys.platform: ## openGL can have a major impact on mac, but als
     useOpenGL = False
     if QtGui.QApplication.instance() is not None:
         print('Warning: QApplication was created before pyqtgraph was imported; there may be problems (to avoid bugs, call QApplication.setGraphicsSystem("raster") before the QApplication is created).')
+    if QtGui.QApplication.setGraphicsSystem:
         QtGui.QApplication.setGraphicsSystem('raster')  ## work around a variety of bugs in the native graphics system 
 else:
     useOpenGL = False  ## on windows there's a more even performance / bugginess tradeoff. 

pyqtgraph/graphicsItems/PlotItem/plotConfigTemplate_pyqt.py

@@ -7,7 +7,7 @@
 #
 # WARNING! All changes made in this file will be lost!
 
-from PyQt4 import QtCore, QtGui
+from ...Qt import QtCore, QtGui
 
 try:
     _fromUtf8 = QtCore.QString.fromUtf8

pyqtgraph/graphicsItems/ViewBox/axisCtrlTemplate_pyqt.py

@@ -7,7 +7,7 @@
 #
 # WARNING! All changes made in this file will be lost!
 
-from PyQt4 import QtCore, QtGui
+from ...Qt import QtCore, QtGui
 
 try:
     _fromUtf8 = QtCore.QString.fromUtf8

pyqtgraph/imageview/ImageViewTemplate_pyqt.py

@@ -7,7 +7,7 @@
 #
 # WARNING! All changes made in this file will be lost!
 
-from PyQt4 import QtCore, QtGui
+from ..Qt import QtCore, QtGui
 
 try:
     _fromUtf8 = QtCore.QString.fromUtf8