[BUG] creating Operation fails with "IndexError: list index out of range in operation_ops.py, line 50"

[wolfgangr]

Describe the Bug
When I try to create a new operation, I get the error message

IndexError: list index out of range
Error: Python: Traceback (most recent call last):
  File "/home/wrosner/.config/blender/4.3/extensions/user_default/fabex/operators/operation_ops.py", line 50, in execute
    view3d = [a for a in context.screen.areas if a.type == "VIEW_3D"][0]
             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^

When I try to load a preset, i get the error message

IndexError: list index out of range
Location: /home/wrosner/test/blender/blender-4.3.2-linux-x64/4.3/scripts/modules/bpy/ops.py:109
Error: Failed to execute the preset: RuntimeError('Error: Python: Traceback (most recent call last):\n  File "/home/wrosner/.config/blender/4.3/extensions/user_default/fabex/operators/operation_ops.py", line 50, in execute\n    view3d = [a for a in context.screen.areas if a.type == "VIEW_3D"][0]\n             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^\nIndexError: list index out of range\nLocation: /home/wrosner/test/blender/blender-4.3.2-linux-x64/4.3/scripts/modules/bpy/ops.py:109\n')
rna_uiItemR: property not found: CAM_MACHINE_Properties.output_g43_on_tool_change
/home/wrosner/.config/blender/4.3/extensions/user_default/fabex/ui/panels/machine_panel.py:111

To Reproduce
Steps to reproduce the behavior:

1. ~/test/blender/blender-4.3.2-linux-x64/blender-launcher
2. Install FabexCNC following https://github.com/vilemduha/blendercam
3. create new blender file and add arbitrary STL (from FreeCAD)
4. ... or (alternatively) ... follow the steps given here: https://blendercam.com/documentation/example-of-project/
5. Go to "Rendering", set Render Engine to Fabex CNC/CAM
6. hit [+] in [ Operations ] property to get started
7. read above error on the screen and on the console

Expected Behavior

Workflow to "Add Pocket and Profile operations" as in
https://blendercam.com/documentation/example-of-project/

System Information:

• OS: debian 10.13 (buster)
• Blender Version: 4.3.2
• Addon Version: [e.g. 1.0.61]

Error Message:
see above

Additional context
??

[wolfgangr]

Thundering silence?

Is this the genuine FabEX CNC repo at all, or did I hit some unmaintained fork?

If BlenderCAM / FabEX CNC is not compatible with recent Blender, may somebody please give me an indication which Version of Blender to install?

edit 1:
https://github.com/vilemduha/blendercam/blob/master/documentation/Blendercam%20Installation.md#obtaining-blender
says "It works now with Blender version 4.21 "

However, I don't find such a thing as "Blender 4.21".
What I can find is a version 4.2.1 - is this the last one supported?
https://download.blender.org/release/Blender4.2/

Or may it be an issue with missing prerequitsites on my old debian buster?

edit 2:
just followed the pointers to the development version, among others looking for python issues:
https://github.com/pppalain/blendercam/blob/master/scripts/addons/docs/faq.md#i-cant-install-or-enable-fabex-whats-going-on

According to that, python 3.11 comes with blender (and there is an included
blender-4.3.2-linux-x64/4.3/python/bin/python3.11)
so I'd rule out a python dependency issue?

Any clue for pinning down the error would be greatly appreciated - many thanks :-)

[wolfgangr]

Same game with Blender 4.2.1 LTS

IndexError: list index out of range
Traceback (most recent call last):
  File "/home/wrosner/.config/blender/4.2/extensions/user_default/fabex/operators/operation_ops.py", line 50, in execute
    view3d = [a for a in context.screen.areas if a.type == "VIEW_3D"][0]
             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^

Regarding python, Blender system info reports
version: 3.11.7 (main, Jun 11 2024, 12:31:01) [GCC 11.2.1 20220127 (Red Hat 11.2.1-9)]

hm.....

May be it's a silly blender bloody beginner issue?
I come from FreeCAD and wanted to try blender for large meshes (sculptures), where FreeCAD obviously hits it's limits.
Could it be that I had to learn the workflow how to render anything at all before trying to produce gcode???

but there is a really simple explicit guide here - and this ends up with the same error...
https://github.com/pppalain/blendercam/blob/master/scripts/addons/docs/starting.md#add-an-operation

[wolfgangr]

same picture with FabEx 1.0.65

hm ... might it be related to the installation openCAMlib for FreeCAD?

I just remeber that the version control machine of pyhton stufff .... well .... has some room for improvement, but not well equipped for the details...

[wolfgangr]

looking into the code, uneducated guess tells me that it might rather not be an issue rootet deep in the nuts'n bolts of CAM

https://github.com/vilemduha/blendercam/blob/83a48aabe37535beb225647001d61e9816e2a45c/scripts/addons/cam/operators/operation_ops.py#L48C7-L51C51

UI incompatibility?
Or just some silly beginner's workflow error not caught yet?

[wolfgangr]

so lets try the crude hack, based on rudimentary python:

... :~/.config/blender/4.3/extensions/user_default/fabex/operators$ diff operation_ops.py_000 operation_ops.py
50,51c50,54
<             view3d = [a for a in context.screen.areas if a.type == "VIEW_3D"][0]
<             view3d.spaces[0].show_region_ui = True
---
>             try:
>                 view3d = [a for a in context.screen.areas if a.type == "VIEW_3D"][0]
>                 view3d.spaces[0].show_region_ui = True
>             except:
>                 pass

whatever the check may assume to come up to set the "True" flag - if anything goes wrong, we won't set it.

Now at least I can create any operation and start to explore FabEX CNC.
I promise to drop a note whether I hit another wall.

I don't think the change is large enough for a PR, is it?

[wolfgangr]

just finished the startup tutorial until
https://github.com/pppalain/blendercam/blob/master/scripts/addons/docs/starting.md#calculate-path-and-generate-gcode

gcode successfully testet in CAMotics.
Looks like my hack did not break anything essential.

Found in the end that maybe my beginners mistake was to switch to "Rendering Workbench" for no no real need.
When I switched back to "Layout Workbench", I still find all CAM settings in the property window.