Cleanup / fixes:

- Corrected isQObjectAlive for PyQt and older PySide
  - Warning messages are opt-in using pg.setConfigOptions(crashWarning=True)

pyqtgraph/Qt.py

@@ -32,8 +32,22 @@ else:
 if USE_PYSIDE:
     from PySide import QtGui, QtCore, QtOpenGL, QtSvg
     import PySide
-    from PySide import shiboken
-    isQObjectAlive = shiboken.isValid
+    try:
+        from PySide import shiboken
+        isQObjectAlive = shiboken.isValid
+    except ImportError:
+        def isQObjectAlive(obj):
+            try:
+                if hasattr(obj, 'parent'):
+                    obj.parent()
+                elif hasattr(obj, 'parentItem'):
+                    obj.parentItem()
+                else:
+                    raise Exception("Cannot determine whether Qt object %s is still alive." % obj)
+            except RuntimeError:
+                return False
+            else:
+                return True
     
     VERSION_INFO = 'PySide ' + PySide.__version__
     
@@ -82,7 +96,8 @@ else:
 
 
     import sip
-    isQObjectAlive = sip.isdeleted
+    def isQObjectAlive(obj):
+        return not sip.isdeleted(obj)
     loadUiType = uic.loadUiType
 
     QtCore.Signal = QtCore.pyqtSignal

pyqtgraph/__init__.py

@@ -56,6 +56,7 @@ CONFIG_OPTIONS = {
     'weaveDebug': False,    ## Print full error message if weave compile fails
     'exitCleanup': True,    ## Attempt to work around some exit crash bugs in PyQt and PySide
     'enableExperimental': False, ## Enable experimental features (the curious can search for this key in the code)
+    'crashWarning': False,  # If True, print warnings about situations that may result in a crash
 } 
 
 
@@ -286,8 +287,10 @@ def cleanup():
     for o in gc.get_objects():
         try:
             if isinstance(o, QtGui.QGraphicsItem) and isQObjectAlive(o) and o.scene() is None:
-                sys.stderr.write(
-                    'Error: graphics item without scene. Make sure ViewBox.close() and GraphicsView.close() are properly called before app shutdown (%s)\n' % (o,))
+                if getConfigOption('crashWarning'):
+                    sys.stderr.write('Error: graphics item without scene. '
+                        'Make sure ViewBox.close() and GraphicsView.close() '
+                        'are properly called before app shutdown (%s)\n' % (o,))
                 
                 s.addItem(o)
         except RuntimeError:  ## occurs if a python wrapper no longer has its underlying C++ object

pyqtgraph/graphicsItems/PlotItem/PlotItem.py

@@ -295,22 +295,20 @@ class PlotItem(GraphicsWidget):
     
     #Important: don't use a settattr(m, getattr(self.vb, m)) as we'd be leaving the viebox alive
     #because we had a reference to an instance method (creating wrapper methods at runtime instead).
-    frame = sys._getframe()
     for m in [
         'setXRange', 'setYRange', 'setXLink', 'setYLink', 'setAutoPan', 'setAutoVisible',
         'setRange', 'autoRange', 'viewRect', 'viewRange', 'setMouseEnabled', 'setLimits',
         'enableAutoRange', 'disableAutoRange', 'setAspectLocked', 'invertY',
         'register', 'unregister']:  ## NOTE: If you update this list, please update the class docstring as well.
-        def _create_method(name):  # @NoSelf
+        def _create_method(name):
             def method(self, *args, **kwargs):
                 return getattr(self.vb, name)(*args, **kwargs)
             method.__name__ = name
             return method
         
-        frame.f_locals[m] = _create_method(m)
+        locals()[m] = _create_method(m)
         
     del _create_method
-    del frame
     
     def setLogMode(self, x=None, y=None):
         """

pyqtgraph/graphicsItems/ViewBox/ViewBox.py

@@ -1655,8 +1655,8 @@ class ViewBox(GraphicsWidget):
         ## called when the application is about to exit.
         ## this disables all callbacks, which might otherwise generate errors if invoked during exit.
         for k in ViewBox.AllViews:
-            if isQObjectAlive(k):
-                sys.stderr.write('ViewBox should be closed before application exit!')
+            if isQObjectAlive(k) and getConfigOption('crashWarning'):
+                sys.stderr.write('Warning: ViewBox should be closed before application exit.\n')
                 
             try:
                 k.destroyed.disconnect()

pyqtgraph/tests/test_qt.py

@@ -0,0 +1,10 @@
+import pyqtgraph as pg
+import gc
+
+def test_isQObjectAlive():
+    o1 = pg.QtCore.QObject()
+    o2 = pg.QtCore.QObject()
+    o2.setParent(o1)
+    del o1
+    gc.collect()
+    assert not pg.Qt.isQObjectAlive(o2)