show_object sometimes does not work

[adam-urbanczyk]

          If it helps, I get the same on Fedora 38 kind of error with CadQuery installed in a Python 3.11 virtual environment. Using the following code:

import cadquery as cq
from cadquery.vis import show

#d = 10  # box is visible as expected
d = 100  # empty window displayed; after 'r' key or zoom with middle mouse the box is displayed

result = cq.Workplane().box(d, d, d)

show(result)

With the #1394 branch I also got:

2023-10-02 23:51:41.837 (   0.491s) [        4D584740]vtkDemandDrivenPipeline:661    ERR| vtkCompositeDataPipeline (0x56454faba5e0): Input port 0 of algorithm vtkTriangleFilter (0x56454ff2f010) has 0 connections but is not optional.
Traceback (most recent call last):
  File "/home/Projects/cadquery/cadquery_vis.py", line 9, in <module>
    show(result)
  File "/home/Projects/cadquery/lib64/python3.11/site-packages/cadquery/vis.py", line 82, in show
    win.SetSize(*win.GetScreenSize())
TypeError: vtkRenderWindow.SetSize() argument after * must be an iterable, not NoneType

Adding a print statement for win.GetScreenSize() and it returns None. The workaround from https://github.com/CadQuery/cadquery/pull/1366#issuecomment-1695614005 results in:

2023-10-03 00:08:51.661 (   0.487s) [        55B74740]vtkDemandDrivenPipeline:661    ERR| vtkCompositeDataPipeline (0x5618c5e38540): Input port 0 of algorithm vtkTriangleFilter (0x5618c6028e70) has 0 connections but is not optional.
X Error of failed request:  BadWindow (invalid Window parameter)
  Major opcode of failed request:  3 (X_GetWindowAttributes)
  Resource id in failed request:  0x0
  Serial number of failed request:  8
  Current serial number in output stream:  9

I'm running on X11, maybe Wayland will work?

Originally posted by @Jopie01 in https://github.com/CadQuery/cadquery/issues/1366#issuecomment-1743842557

[Jopie01]

Ok, after a bit more digging it seems something goes wrong with OCP. The line https://github.com/CadQuery/cadquery/blob/d7801273704134fdb172e3c6ac22d34d326e2800/cadquery/occ_impl/shapes.py#L1335 returns None so no data is returned.

I downgraded cadquery-ocp to version 7.7.0 with pip install --upgrade cadquery-ocp==7.7.0 and voilà ..... I got a cube!

/cc @rohit-kumar-j and @joaotcarvalho are you both able to downgrade to cadquery-ocp version 7.7.0 and see it that also works for you?

[rohit-kumar-j]

Nice! This works for me on windows.

[adam-urbanczyk]

OK, so all this was with the pip package. Can you also reproduce this with the OCP conda package from conda-forge?