[Backport] Add facility to set task done callback

- on async signal handlers
(originally provided by @usiems)

(cherry picked from commit MeVisLab/pythonqt@575c51f)

Author: mrbean-bremen

src/PythonQt.cpp

@@ -274,6 +274,7 @@ void PythonQt::init(int flags, const QByteArray& pythonQtModuleName)
     }
 
     _self->priv()->pythonQtModule().addObject("Debug", _self->priv()->_debugAPI);
+    _self->priv()->pythonQtModule().addObject("Config", _self->priv()->_configAPI);
 
     Py_INCREF((PyObject*)&PythonQtSlotDecorator_Type);
     Py_INCREF((PyObject*)&PythonQtSignalFunction_Type);
@@ -400,6 +401,11 @@ PythonQtPrivate::~PythonQtPrivate() {
   PythonQtArgumentFrame::cleanupFreeList();
 }
 
+void PythonQtPrivate::setTaskDoneCallback(const PythonQtObjectPtr & callable)
+{
+  _pyTaskDoneCallback = callable;
+}
+
 void PythonQt::setRedirectStdInCallback(PythonQtInputChangedCB* callback, void * callbackData)
 {
   if (!callback) {
@@ -1440,6 +1446,7 @@ PythonQtPrivate::PythonQtPrivate()
   _hadError = false;
   _systemExitExceptionHandlerEnabled = false;
   _debugAPI = new PythonQtDebugAPI(this);
+  _configAPI = new PythonQtConfigAPI(this);
 }
 
 void PythonQtPrivate::setupSharedLibrarySuffixes()

src/PythonQt.h

@@ -663,6 +663,7 @@ class PYTHONQT_EXPORT PythonQt : public QObject {
 };
 
 class PythonQtDebugAPI;
+class PythonQtConfigAPI;
 
 //! internal PythonQt details
 class PYTHONQT_EXPORT PythonQtPrivate : public QObject {
@@ -681,6 +682,10 @@ class PYTHONQT_EXPORT PythonQtPrivate : public QObject {
     AllDecorators = 0xffff
   };
 
+  //! Set a callable that is used as the argument for the add_done_callback for the Task
+  //! created by checkAndRunCoroutine
+  void setTaskDoneCallback(const PythonQtObjectPtr& callable);
+
   //! get the suffixes that are used for shared libraries
   const QStringList& sharedLibrarySuffixes() { return _sharedLibrarySuffixes; }
 
@@ -861,6 +866,8 @@ class PYTHONQT_EXPORT PythonQtPrivate : public QObject {
   PythonQtObjectPtr _pySourceFileLoader;
   PythonQtObjectPtr _pySourcelessFileLoader;
 
+  PythonQtObjectPtr _pyTaskDoneCallback;
+
   //! the cpp object wrapper factories
   QList<PythonQtCppWrapperFactory*> _cppWrapperFactories;
 
@@ -873,6 +880,7 @@ class PYTHONQT_EXPORT PythonQtPrivate : public QObject {
   PythonQt::ProfilingCB* _profilingCB;
 
   PythonQtDebugAPI* _debugAPI;
+  PythonQtConfigAPI* _configAPI;
 
   int _initFlags;
   int _PythonQtObjectPtr_metaId;

src/PythonQtStdDecorators.cpp

@@ -354,6 +354,17 @@ const QMetaObject* PythonQtStdDecorators::metaObject( QObject* obj )
   return obj->metaObject();
 }
 
+//---------------------------------------------------------------------------
+
+void PythonQtConfigAPI::setTaskDoneCallback(PyObject* object)
+{
+  if (PythonQt::self()) {
+    PythonQt::self()->priv()->setTaskDoneCallback(object);
+  }
+}
+
+//---------------------------------------------------------------------------
+
 bool PythonQtDebugAPI::isOwnedByPython( PyObject* object )
 {
   if (PyObject_TypeCheck(object, &PythonQtInstanceWrapper_Type)) {

src/PythonQtStdDecorators.h

@@ -173,6 +173,20 @@ public Q_SLOTS:
 
 };
 
+//! Some methods to set properties of PythonQt from Python
+class PYTHONQT_EXPORT PythonQtConfigAPI : public QObject
+{
+  Q_OBJECT
+public:
+  PythonQtConfigAPI(QObject* parent):QObject(parent) {};
+
+public slots:
+  //! Set a callable that is used as the argument for the add_done_callback for the Task/Future
+  //! created when, e.g., an async function is connected to signal.
+  void setTaskDoneCallback(PyObject* object);
+};
+
+
 //! Some helper methods that allow testing of the ownership
 class PYTHONQT_EXPORT PythonQtDebugAPI : public QObject
 {