Overriden WndProc() method on Form control in WinForms is never getting called #2536

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1. proneon267 commented on Jan 1, 2025

   

   proneon267

   on Jan 1, 2025

   Author

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   For anyone else who might need it, we can achieve the same using win32 APIs directly:

   import clr
   
   clr.AddReference("System.Windows.Forms")
   clr.AddReference("System.Drawing")
   
   from System.Windows.Forms import Form, Application
   from System.Drawing import Size
   import ctypes
   from ctypes import wintypes
   
   # Define necessary constants and functions
   GWL_WNDPROC = -4
   WM_CLOSE = 0x0010  # Example: close message
   
   # Define SetWindowLongPtrW
   windll = ctypes.WinDLL('user32', use_last_error=True)
   SetWindowLongPtr = windll.SetWindowLongPtrW
   SetWindowLongPtr.argtypes = [wintypes.HWND, wintypes.INT, ctypes.c_void_p]
   SetWindowLongPtr.restype = ctypes.c_void_p
   
   # Define GetWindowLongPtrW
   GetWindowLongPtr = windll.GetWindowLongPtrW
   GetWindowLongPtr.argtypes = [wintypes.HWND, wintypes.INT]
   GetWindowLongPtr.restype = ctypes.c_void_p
   
   # Define CallWindowProcW
   CallWindowProc = windll.CallWindowProcW
   CallWindowProc.argtypes = [
       ctypes.c_void_p,
       wintypes.HWND,
       wintypes.UINT,
       wintypes.WPARAM,
       wintypes.LPARAM,
   ]
   CallWindowProc.restype = ctypes.c_long
   
   
   class MyForm(Form):
       def __init__(self):
           super().__init__()
           self.Text = "WndProc Example"
           self.Size = Size(300, 200)
   
           # Get the window procedure (WndProc) for the window
           self.original_wndproc = GetWindowLongPtr(self.Handle.ToInt64(), GWL_WNDPROC)
           print(f"Original WndProc: {self.original_wndproc}")
   
           # Create a callback for the window procedure
           WNDPROC = ctypes.WINFUNCTYPE(
               ctypes.c_long,
               wintypes.HWND,
               wintypes.UINT,
               wintypes.WPARAM,
               wintypes.LPARAM,
           )
   
           # Register our WndProc to handle window messages
           self.wndproc_callback = WNDPROC(self.WndProc)
           SetWindowLongPtr(
               self.Handle.ToInt64(),
               GWL_WNDPROC,
               ctypes.cast(self.wndproc_callback, ctypes.c_void_p),
           )
   
           current_wndproc = GetWindowLongPtr(self.Handle.ToInt64(), GWL_WNDPROC)
           print(f"Current WndProc: {current_wndproc}")
   
       def WndProc(self, hwnd, msg, w_param, l_param):
           print(
               f"WndProc called: hwnd={hwnd}, msg={msg}, w_param={w_param}, l_param={l_param}"
           )
   
           # Handle specific message (for example, WM_CLOSE)
           if msg == WM_CLOSE:
               print("Window is closing.")
               return 0  # Prevent default close handling
   
           # Call the original window procedure for default handling
           return CallWindowProc(self.original_wndproc, hwnd, msg, w_param, l_param)
   
   
   # Run the application and create an instance of the form
   Application.Run(MyForm())

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2. proneon267 commented on Feb 5, 2025

   

   proneon267

   on Feb 5, 2025

   Author

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   Perhaps this is a duplicate of #2192, so close this issue as per your discretion.
3. lostmsu

   closed this as a duplicateof Support overriding protected virtual methods of a .NET class in Python #2192 on Apr 11, 2025