Error interpreting message in nativeEvent on Windows (might be a Qt bug?)

berry36

Minimal example:

from PySide6.QtWidgets import QWidget, QApplication

class Window(QWidget):
    def nativeEvent(self, eventType, message):
        print(eventType, message, message.toBytes())
        return super().nativeEvent(eventType, message)

app = QApplication()
window = Window()
window.show()
app.exec()

The output is always like

b'windows_generic_MSG' shiboken6.Shiboken.VoidPtr(Address 0x000000765B8DBD20, Size 0, isWritable False) b''

According to information on the Internet and the docs (Python doc, C++ doc), I am supposed to convert message to a Windows MSG.

From the documentation of shiboken6.Shiboken.VoidPtr, the only way to access data from a Shiboken.VoidPtr is .toBytes(). But message.toBytes() is always returning b''. And the "Size" of message is always zero.

My plan was to use struct module to convert the bytes (though I'm not sure if struct is the right way):

from PySide6.QtWidgets import QWidget, QApplication
from shiboken6 import Shiboken
import struct

class Window(QWidget):
    def nativeEvent(self, eventType, message):
        if eventType == b'windows_generic_MSG':
            bytes = message.toBytes()
            # https://learn.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-msg
            # https://learn.microsoft.com/en-us/windows/win32/winprog/windows-data-types
            msg = struct.unpack("PIPPLllL", bytes)
            print(f"Bytes: {bytes!r} Interpreted: {msg}")
        return super().nativeEvent(eventType, message)

app = QApplication()
window = Window()
window.show()
app.exec()

Which does not work since the data is always empty:

Traceback (most recent call last):
  File "d:\documents\temp2.py", line 33, in <module>
    window.show()
    ~~~~~~~~~~~^^
  File "d:\documents\temp2.py", line 26, in nativeEvent
    msg = struct.unpack("PIPPLllL", bytes)
struct.error: Error calling Python override of QWidget::nativeEvent(): unpack requires a buffer of 48 bytes

I tried this:

    def nativeEvent(self, eventType, message):
        if eventType == b'windows_generic_MSG':
            message2 = Shiboken.VoidPtr(message, 48)
            bytes = message2.toBytes()
            print(message2, bytes)
            msg = struct.unpack("PIPPLllL", bytes)
            print(f"Bytes: {bytes!r} Interpreted: {msg}")
        return super().nativeEvent(eventType, message)

It does not seem to change anything:

shiboken6.Shiboken.VoidPtr(Address 0x000000D9360DE0D0, Size 0, isWritable False) b''
shiboken6.Shiboken.VoidPtr(Address 0x000000D9360DEC40, Size 0, isWritable False) b''
... more lines like above
Traceback (most recent call last):
  File "d:\documents\temp2.py", line 28, in <module>
    window.show()
    ~~~~~~~~~~~^^
  File "d:\documents\temp2.py", line 12, in nativeEvent
    msg = struct.unpack("PIPPLllL", bytes)
struct.error: Error calling Python override of QWidget::nativeEvent(): unpack requires a buffer of 48 bytes

And this:

    def nativeEvent(self, eventType, message):
        if eventType == b'windows_generic_MSG':
            message.size = 48
            bytes = message.toBytes()
            print(message, bytes)
            msg = struct.unpack("PIPPLllL", bytes)
            print(f"Bytes: {bytes!r} Interpreted: {msg}")
        return super().nativeEvent(eventType, message)

No good either:

Traceback (most recent call last):
  File "d:\documents\temp2.py", line 28, in <module>
    window.show()
    ~~~~~~~~~~~^^
  File "d:\documents\temp2.py", line 9, in nativeEvent
    message.size = 48
    ^^^^^^^^^^^^
AttributeError: Error calling Python override of QWidget::nativeEvent(): 'shiboken6.Shiboken.VoidPtr' object has no attribute 'size' and no __dict__ for setting new attributes

Is this a bug or is it me missing something? Does anybody know how I can read a native event from nativeEvent()? (Let's say that I don't have an objective further than that and just want to understand the event data)

berry36

I decided to go ahead and submit an issue because I feel like it is likely a bug.