TODO.txt

 * Documentation
 * Implement a way to properly handle multiline interactive input including pastes (could be through qtconsole)
 * Implement dropped-connection detection so that resources from a thread that gets stuck and its connection dropped are freed. This would probably require a complete revamp of how connections are handled because the current asyncio method is incapable of detection of a dropped connection during processing. It would require some level of cooperation from wait functions because they would have to cease their wait and raise an exception when the detect a connection dropped flag (thread interruption is not safe in general).
 * Define a settings-savings protocol (.queryall() method)
 * Need convention for include-guarding to prevent unintentional multiple include()s of the same functionality?
 

 * QT Principles (proposed):
    * We should try to work with both PySide2 and PyQt5 (RHEL 8 for example include PyQt5 but not PySide2)
    * QWidget derived classes must live in the main loop context
    * Ideally they make only asynchronous calls to dgpy modules, which will be dispatched from some helper thread pool. 
    * The QT Wrappers module can be used to call QWidget methods back from
      outside (either synchronously or asynchronously)
    * Unfortunately this will make widgets unnecessarily complicated
    * Implement synchronous calls via creating sub-qeventloop's.
      * Be warned that your widget's C++ base object may disappear (e.g. due to deleteLater())
        in the middle of your method execution if you make such a synchronous call.
	The object deletion can be detected by not(shiboken2.isValid(self)) or PyQt5.sip.isdeleted(self)
	(which we should really wrap for consistency). Otherwise you will get exceptions like
	"RuntimeError: Internal C++ object already deleted"
	https://stackoverflow.com/questions/11328219/how-to-know-if-object-gets-deleted-in-python
     * For matplotlib specifically the callbacks (mpl_connect())  can be treated as asynchronous
       but need to be specially wrapped so that they don't try to run in the main thread.
     * Also see for example the bugs described here: https://www.youtube.com/watch?v=ol5IuJyw-Tg : https://bugreports.qt.io/browse/PYSIDE-810 and https://bugreports.qt.io/browse/PYSIDE-813 for illustrations of how tricky some of these things can be. It would appear that thse bugs are fixed in both pyside2 and pyqt5. For PYSIDE-810 at least for pyside2 the fix was explicitly shifting all qwidget destruction to the main thread (in which case we don't have to worry about that ourselves)
   * spatialnde2 QTRecViewer needs to be run in the main thread. Since spatialnde2 basically doesn't do
     callbacks except via derived classes, and derived classes shouldn't be calling dgpython modules
     there isn't much of an issue (and 99% of spatialnde2 would be in other threads anyway!).