Import pymeshlab causes global QT conflicts

[arattner1]

I have had success using pymeshlab for some filtering. I was trying to add my code to a bigger project that interfaces with another software tool that uses QT (specifically pyfluent for ANSYS Fluent).

It appears that the pymeshlab init method on import changes some global environment variables in a way that causes other QT using packages (like ANSYS Fluent to fail). I am running code in Windows for reference.

Here is an example to reproduce the issue for me:

Works

import ansys.fluent.core as pyfluent
from ansys.fluent.core import Meshing

meshing_session = pyfluent.launch_fluent( mode=pyfluent.FluentMode.MESHING, precision=pyfluent.Precision.DOUBLE, processor_count=4, product_version='252', dimension=pyfluent.Dimension.THREE, ui_mode=pyfluent.UIMode.GUI)

Fails (ANSYS Fluent fails to launch)

import pymeshlab as ml

import ansys.fluent.core as pyfluent
from ansys.fluent.core import Meshing

meshing_session = pyfluent.launch_fluent( mode=pyfluent.FluentMode.MESHING, precision=pyfluent.Precision.DOUBLE, processor_count=4, product_version='252', dimension=pyfluent.Dimension.THREE, ui_mode=pyfluent.UIMode.GUI)

The second example fails with the following error:

qt.qpa.plugin: Could not load the Qt platform plugin "windows" in "" even though it was found. This application failed to start because no Qt platform plugin could be initialized...

I suspect this is due to some setup commands at the top of pymeshlab init.py . Probably the following:

# for windows we need to tell which Qt libraries use
this_path = str(pathlib.Path(__file__).parent.absolute())
if platform == 'win32':
    os.environ['QT_PLUGIN_PATH'] = this_path
    os.environ['PATH'] = this_path + os.pathsep + os.environ['PATH']

Thanks for any assistance on this issue!

[arattner1]

I did come up with a silly workaround. I import pymeshlab each time it is needed inside a function, and manually reset the environment variables after use:

def my_method(self):
       #For some reason, pymeshlab does something to the qt environment variables that causes fluent to fail to launch?
       #So keep the affected variables in backup before loading pymeshlab
       PATH_i = os.environ['PATH']
       QT_PLUGIN_PATH_existed = 'QT_PLUGIN_PATH' in os.environ
       if QT_PLUGIN_PATH_existed:
           QT_PLUGIN_PATH_i = os.environ['QT_PLUGIN_PATH']
       
       import pymeshlab as ml
       
       ...

       #Revert environment variables modified by loading pymeshlab
       os.environ['PATH'] = PATH_i

       if QT_PLUGIN_PATH_existed:
           os.environ['QT_PLUGIN_PATH'] = QT_PLUGIN_PATH_i
       elif 'QT_PLUGIN_PATH' in os.environ:
           del os.environ['QT_PLUGIN_PATH']