Bug or feature (or just not jet implemented) in canvas copy

Hi,

Having a sketchpad with a line (names "B") and an arrow (named "A") I would expect naively that the following code:

from openexp.mouse import mouse
my_mouse = mouse(exp)
my_canvas = self.copy_sketchpad("welcome")
my_Arrow = my_canvas['A']
my_Line = my_canvas['B']

while True:
pos, time = my_mouse.get_pos()
    my_Arrow.ex = pos[0]
    my_Arrow.ey = pos[1]
    my_Line.ex = pos[0]
    my_Line.ey = pos[1]
    my_canvas.show()

Would let both arrow and line endings to follow my mouse pointer. But:

With the "Psycho" and "Xpyriment" back-ends, only the line-ending follows,The arrow stays unchanged

With the "legacy" back-end, I get the following error:

 File "C:\Program Files (x86)\OpenSesame\Lib\site-packages\libopensesame\inline_script.py", line 116, in run
  self.workspace._exec(self.crun)
 File "C:\Program Files (x86)\OpenSesame\Lib\site-packages\libopensesame\base_python_workspace.py", line 124, in _exec
  exec(bytecode, self._globals)
 Inline script, line 4, in <module>
 File "C:\Program Files (x86)\OpenSesame\Lib\site-packages\libopensesame\inline_script.py", line 183, in copy_sketchpad
  c.copy(self.experiment.items[sketchpad_name].canvas)
 File "C:\Program Files (x86)\OpenSesame\Lib\site-packages\openexp\_canvas\legacy.py", line 158, in copy
  Canvas.copy(self, canvas)
 File "C:\Program Files (x86)\OpenSesame\Lib\site-packages\openexp\_canvas\canvas.py", line 784, in copy
  for name, element in canvas._elements.items()
 File "C:\Program Files (x86)\OpenSesame\Lib\site-packages\openexp\_canvas\canvas.py", line 784, in <listcomp>
  for name, element in canvas._elements.items()
 File "C:\Program Files (x86)\OpenSesame\Lib\site-packages\openexp\_canvas\_element\legacy.py", line 47, in copy
  return self.__class__(canvas, **properties)
TypeError: __init__() missing 4 required positional arguments: 'sx', 'sy', 'ex', and 'ey' 

So apparently the copy function chokes.

When removing the arrow, the legacy back-end does allow me to copy the canvas.

I am trying to create a plugin, and there I seem to be unable to use copy_sketchpad. There I use Canvas.copy on the canvas element of the sketchpad item, and see the same behavior.

Regards,

Mark