Eventfilter in python plugins do not work as expected

[amibranch]

Environment information

• Operating System: Arch Linux
• Cutter version: a5442f6f99bbd1f150e8dcaa4d671c3049cec917 (more recent HEAD, build and installed via custom PKGBUILD)
• Obtained from:
  • Built from source
  • Downloaded release from Cutter website or GitHub
  • Distribution repository
• File format: arbitrary

Describe the bug

I was trying to create a python plugin for cutter that provides part of the ARM documentation in the disassembly-view as tooltip. Basically a clone of AMIE for cutter.

While trying to install an eventfilter on the cutter mainwindow, I discovered that the events will only pass my eventfilter if I raise an exception in the setupInterface function of my plugin.

To Reproduce

1. Install cutter for linux
2. Create a python plugin with the following content

#!/usr/bin/env python3

import sys

import cutter

from qtpy.QtCore import QObject

class MyEventFilter(QObject):
    def eventFilter(self, watched, event):
        print(f"Reached {event.type()} on {watched}")
        return super().eventFilter(watched, event)

class MyPlugin(cutter.CutterPlugin):
    name = "My Plugin"
    description = "A Minimalist Python plugin"
    version = "1.0"
    author = "amibranch"

    def setupInterface(self, main):
        obj = main
        event_filter = MyEventFilter()
        obj.setMouseTracking(True)
        obj.installEventFilter(event_filter)

        # Will work:
        raise ValueError('A very specific bad thing happened.')

        # Won't work:
        #return

    def setupPlugin(self):
        pass

    def terminate(self):
        pass

def create_cutter_plugin():
    return MyPlugin()

3. Copy the plugin into a folder that will be used by cutter on default. E.g. ~/.local/share/rizin/cutter/plugins/python/
4. Start cutter (at best from shell to observe stdout/stderr therein) and load an arbitrary project
5. If you leave the exception in the code, the eventfilter will work as expected. If you remove it (i.e. leave just a return) it will not!

Expected behavior

• I expect to have the possibility to add eventfilter to cutter main windows, in order to use them as intended by qtpy/pyside (without raising any exceptions that may introduce sideeffects.

Additional context

I figured out that the main difference is the execution of setupInterface from within cutter (CutterPluginWrapper::setupInerface). In case of an exception pyResult is denoted by gdb as:

(gdb) p pyResult
$2 = {m_pyObj = 0x0}

However, the impact of the following Shiboken::Errors::storePythonOverrideErrorOrPrint is beyond my knowledge of shiboken-/cutter-internals.