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Loading DLL in Cura


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Posted · Loading DLL in Cura

Hey forum,


I am trying to use a DLL inside a cura plugin but for some reason it wil not load the DLL for me.

i have a DLL set up that gives coordinates comming from our eye tracker and sends them to the python script.

i have a python script (Script A) that calls this DLL and has a few easy calls for other python scripts to use.


Calling Script A from command line (going through __main__) it loads the DLL and starts outputting coords in a while loop on my cmd window.

When trying to use this Script A in another Script B it does not seem to load the DLL.


Error Message:


2020-08-06 13:45:26,268 - ERROR - [MainThread] UM.Logger.logException [84]: Exception: Error loading plugin PrepareStageSR:
2020-08-06 13:45:26,271 - ERROR - [MainThread] UM.Logger.logException [88]: Traceback (most recent call last):
2020-08-06 13:45:26,273 - ERROR - [MainThread] UM.Logger.logException [88]:   File "D:\Git\Cura Project\Uranium\UM\PluginRegistry.py", line 379, in loadPlugin
2020-08-06 13:45:26,274 - ERROR - [MainThread] UM.Logger.logException [88]:     to_register = plugin.register(self._application)  # type: ignore  # We catch AttributeError on this in case register() doesn't exist.
2020-08-06 13:45:26,276 - ERROR - [MainThread] UM.Logger.logException [88]:   File "D:\Git\Cura Project\Cura\cura\..\plugins\PrepareStageSR\__init__.py", line 19, in register
2020-08-06 13:45:26,278 - ERROR - [MainThread] UM.Logger.logException [88]:     "stage": PrepareStage.PrepareStage()
2020-08-06 13:45:26,280 - ERROR - [MainThread] UM.Logger.logException [88]:   File "D:\Git\Cura Project\Cura\cura\..\plugins\PrepareStageSR\PrepareStage.py", line 14, in __init__
2020-08-06 13:45:26,281 - ERROR - [MainThread] UM.Logger.logException [88]:     sr = SR()
2020-08-06 13:45:26,282 - ERROR - [MainThread] UM.Logger.logException [88]:   File "D:\Git\Cura Project\Cura\cura\..\plugins\PrepareStageSR\SR_EyeCoords.py", line 36, in __init__
2020-08-06 13:45:26,283 - ERROR - [MainThread] UM.Logger.logException [88]:     self.c_lib = ctypes.CDLL("SRPython")
2020-08-06 13:45:26,284 - ERROR - [MainThread] UM.Logger.logException [88]:   File "C:\Users\tom.hendriks\AppData\Local\Programs\Python\Python35\lib\ctypes\__init__.py", line 351, in __init__
2020-08-06 13:45:26,286 - ERROR - [MainThread] UM.Logger.logException [88]:     self._handle = _dlopen(self._name, mode)
2020-08-06 13:45:26,287 - ERROR - [MainThread] UM.Logger.logException [88]: OSError: [WinError 126] The specified module could not be found

my "SR_EyeCoords.py" (calling __main__ does work!)

import ctypes
import pathlib
import time

class SR_Eye:
	__slots__ = ["x", "y", "z"]
	def __init__(self, x=0, y=0, z=0):
		self.x = x
		self.y = y
		self.z = z
	def __str__(self):
		return (str(self.x) + ", " + str(self.y) + ", " + str(self.z))

class SR_EyePair:
	__slots__ = ["left", "right"]
	def __init__(self, left, right):
		self.left = left
		self.right = right
	def __str__(self):
		return (str(self.left) + " : " + str(self.right))

class SR:
	def __init__(self):
		self.c_lib = ctypes.CDLL("SRPython")
		self.c_lib.GetEyeValue.restype = ctypes.c_float
	def GetCurrentEyePair(self):
		lx = self.c_lib.GetEyeValue(0,0)
		ly = self.c_lib.GetEyeValue(0,1)
		lz = self.c_lib.GetEyeValue(0,2)
		rx = self.c_lib.GetEyeValue(1,0)
		ry = self.c_lib.GetEyeValue(1,1)
		rz = self.c_lib.GetEyeValue(1,2)
		eyeL = SR_Eye(lx,ly,lz)
		eyeR = SR_Eye(rx,ry,rz)
		eyePair = SR_EyePair(eyeL, eyeR)
		return eyePair
if __name__ == '__main__':
	# SR_EyeCoords.py executed as script outputs eye Coord every second
	sr = SR()
	while 1:
		time.sleep(1) #sleep for 1 second

Snippet of the PrepareStage.py (using a coppy of the normal preparestage as a base since i'm not that familiar with the plugin development yet)


from cura.Stages.CuraStage import CuraStage

from PrepareStageSR.SR_EyeCoords import *

##  Stage for preparing model (slicing).
class PrepareStage(CuraStage):
    def __init__(self, parent = None):
        sr = SR()                                      #crash on this line
        eyePair = sr.GetCurrentEyePair()


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    Posted · Loading DLL in Cura

    I think you need to look at where the DLL is located relative to Cura's working directory. Cura's working directory is the user home unless executed from the command line. So it's probably better to just give it a full path.


    Look into PluginRegistry.getPluginPath to get the absolute path to your plug-in's directory, and combine that with the filename of your DLL.

    I must say though that I've never worked with loading DLLs using CTypes. My SVGToolpathReader works with a DLL (FreeType) that has Python bindings, so that behaves just like any normal module and I can just import it.

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