Experiment a bit with python abc abstractmethod

source/carla_patchbay.py

@@ -94,7 +94,7 @@ class PluginInfo(object):
 # ------------------------------------------------------------------------------------------------
 # Patchbay widget
 
-class CarlaPatchbayW(QFrame):
+class CarlaPatchbayW(QFrame, PluginEditParentMeta, metaclass=PyQtMetaClass):
     def __init__(self, parent, doSetup = True, onlyPatchbay = True, is3D = False):
         QFrame.__init__(self, parent)
 
@@ -391,10 +391,19 @@ class CarlaPatchbayW(QFrame):
     # -----------------------------------------------------------------
     # called by PluginEdit to plugin skin parent, ignored here
 
+    def recheckPluginHints(self, hints):
+        pass
+
     def editDialogChanged(self, visible):
         pass
 
-    def recheckPluginHints(self, hints):
+    def parameterValueChanged(self, parameterId, value):
+        pass
+
+    def programChanged(self, index):
+        pass
+
+    def midiProgramChanged(self, index):
         pass
 
     def notePressed(self, note):

source/carla_shared.py

@@ -29,14 +29,19 @@ import sys
 
 if config_UseQt5:
     from PyQt5.Qt import PYQT_VERSION_STR
-    from PyQt5.QtCore import qFatal, qVersion, qWarning, QDir
+    from PyQt5.QtCore import pyqtWrapperType, qFatal, qVersion, qWarning, QDir
     from PyQt5.QtGui import QIcon
     from PyQt5.QtWidgets import QFileDialog, QMessageBox
 else:
     from PyQt4.Qt import PYQT_VERSION_STR
-    from PyQt4.QtCore import qFatal, qVersion, qWarning, QDir
+    from PyQt4.QtCore import pyqtWrapperType, qFatal, qVersion, qWarning, QDir
     from PyQt4.QtGui import QFileDialog, QIcon, QMessageBox
 
+# ------------------------------------------------------------------------------------------------------------
+# Import ABC
+
+from abc import ABCMeta, abstractmethod
+
 # ------------------------------------------------------------------------------------------------------------
 # Import Signal
 
@@ -636,3 +641,9 @@ def CustomMessageBox(parent, icon, title, text, extraText="", buttons=QMessageBo
     return msgBox.exec_()
 
 # ------------------------------------------------------------------------------------------------------------
+# An empty class used to resolve metaclass conflicts between ABC and PyQt modules
+
+class PyQtMetaClass(pyqtWrapperType, ABCMeta):
+    pass
+
+# ------------------------------------------------------------------------------------------------------------

source/carla_skin.py

@@ -47,7 +47,7 @@ from pixmapdial import PixmapDial
 # ------------------------------------------------------------------------------------------------------------
 # Abstract plugin slot
 
-class AbstractPluginSlot(QFrame):
+class AbstractPluginSlot(QFrame, PluginEditParentMeta, metaclass=PyQtMetaClass):
     def __init__(self, parent, pluginId):
         QFrame.__init__(self, parent)
 

source/carla_widgets.py

@@ -25,11 +25,11 @@ from carla_config import *
 # Imports (Global)
 
 if config_UseQt5:
-    from PyQt5.QtCore import pyqtSignal, pyqtSlot, Qt, QByteArray, QSettings, QTimer
+    from PyQt5.QtCore import pyqtSignal, pyqtSlot, pyqtWrapperType, Qt, QByteArray, QSettings, QTimer
     from PyQt5.QtGui import QColor, QCursor, QFontMetrics, QPainter, QPainterPath
     from PyQt5.QtWidgets import QDialog, QInputDialog, QLineEdit, QMenu, QVBoxLayout, QWidget
 else:
-    from PyQt4.QtCore import pyqtSignal, pyqtSlot, Qt, QByteArray, QSettings, QTimer
+    from PyQt4.QtCore import pyqtSignal, pyqtSlot, pyqtWrapperType, Qt, QByteArray, QSettings, QTimer
     from PyQt4.QtGui import QColor, QCursor, QFontMetrics, QPainter, QPainterPath
     from PyQt4.QtGui import QDialog, QInputDialog, QLineEdit, QMenu, QVBoxLayout, QWidget
 
@@ -394,6 +394,38 @@ class PluginParameter(QWidget):
     def _textCallBack(self):
         return gCarla.host.get_parameter_text(self.fPluginId, self.fParameterId)
 
+# ------------------------------------------------------------------------------------------------------------
+# Plugin Editor Parent (Meta class)
+
+class PluginEditParentMeta(metaclass=ABCMeta):
+    @abstractmethod
+    def recheckPluginHints(self, hints):
+        raise NotImplementedError
+
+    @abstractmethod
+    def editDialogChanged(self, visible):
+        raise NotImplementedError
+
+    @abstractmethod
+    def parameterValueChanged(self, parameterId, value):
+        raise NotImplementedError
+
+    @abstractmethod
+    def programChanged(self, index):
+        raise NotImplementedError
+
+    @abstractmethod
+    def midiProgramChanged(self, index):
+        raise NotImplementedError
+
+    @abstractmethod
+    def notePressed(self, note):
+        raise NotImplementedError
+
+    @abstractmethod
+    def noteReleased(self, note):
+        raise NotImplementedError
+
 # ------------------------------------------------------------------------------------------------------------
 # Plugin Editor (Built-in)
 
@@ -405,6 +437,9 @@ class PluginEdit(QDialog):
         self.ui = ui_carla_edit.Ui_PluginEdit()
         self.ui.setupUi(self)
 
+        if False:
+            parent = PluginEditParent()
+
         # -------------------------------------------------------------
         # Internal stuff