Python curve hook operators mess with selection (Probably only on Windows) #74888

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Demeter Dzadik · 2020-03-18T17:01:11+01:00

Demeter Dzadik commented

2020-03-18 17:01:11 +01:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.20

Blender Version
Broken: version: 2.83 (sub 9), branch: master, commit date: 2020-03-15 22:43, hash: f06a6e92bc
Worked: I tried an older version which I know to have worked on my Linux machine at work a few days ago, and it still didn't work, so I suspect this issue is only present on Windows, or only on my computer. Let me know if you can reproduce.

Exact steps for others to reproduce the error
python_curve_select_bug.blend

Run the python script curve_select_fail.py.
Hook modifiers get added. According to the code, the modifiers should correspond to each curve point. Instead, the result is random - most of the time, but not always, only the first point is hooked with all of the modifiers.
Run the python script why_index_error.py
It index errors. If you remove the last line of code, it works. The last line of code shouldn't affect the curve's indicies, so this can't be right.

LYnrN6gUUu.mp4

I could really use a workaround until this is fixed.

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.20 **Blender Version** Broken: version: 2.83 (sub 9), branch: master, commit date: 2020-03-15 22:43, hash: `f06a6e92bc` Worked: I tried an older version which I know to have worked on my Linux machine at work a few days ago, and it still didn't work, so I suspect this issue is only present on Windows, or only on my computer. Let me know if you can reproduce. **Exact steps for others to reproduce the error** [python_curve_select_bug.blend](https://archive.blender.org/developer/F8414122/python_curve_select_bug.blend) - Run the python script `curve_select_fail.py`. - Hook modifiers get added. According to the code, the modifiers should correspond to each curve point. Instead, the result is random - most of the time, but not always, only the first point is hooked with all of the modifiers. - Run the python script `why_index_error.py` - It index errors. If you remove the last line of code, it works. The last line of code shouldn't affect the curve's indicies, so this can't be right. [LYnrN6gUUu.mp4](https://archive.blender.org/developer/F8414129/LYnrN6gUUu.mp4) I could really use a workaround until this is fixed.

Demeter Dzadik commented

2020-03-18 17:01:11 +01:00

Added subscriber: @Mets

Germano Cavalcante commented

2020-03-19 23:00:25 +01:00

Added subscribers: @ideasman42, @mano-wii

Germano Cavalcante commented

2020-03-19 23:00:25 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Germano Cavalcante commented

2020-03-19 23:00:25 +01:00

The problem is quite complex.

The operator OBJECT_OT_hook_add_selob calls ED_curve_editnurb_load which creates another cu->nurb and free the old one.
But the old cu->nurb is already referenced by a PyObject of type pyrna_prop_collection_Type with pointer inited in rna_Curve_splines_begin.
The ideal would be, when freeing the pointer, to call RNA_POINTER_INVALIDATE(nu_ptr) for the original PointerRNA.
But the question is, how to find this PointerRNA in the operator?

@ideasman42, we need an RNA/CPython expert here.

The problem is quite complex. The operator `OBJECT_OT_hook_add_selob` calls `ED_curve_editnurb_load` which creates another `cu->nurb` and free the old one. But the old `cu->nurb` is already referenced by a `PyObject` of type `pyrna_prop_collection_Type` with pointer inited in `rna_Curve_splines_begin`. The ideal would be, when freeing the pointer, to call `RNA_POINTER_INVALIDATE(nu_ptr)` for the original `PointerRNA`. But the question is, how to find this `PointerRNA` in the operator? @ideasman42, we need an RNA/CPython expert here.

Germano Cavalcante commented

2020-03-19 23:32:16 +01:00

Or maybe we don't even need free cu->nurb

Or maybe we don't even need free `cu->nurb`

Demeter Dzadik commented

2020-03-20 12:30:34 +01:00

Thanks for looking into it! Were you able to reproduce it on Linux as well? I could swear that this worked on my work computer just a few days ago... I will check if I get the chance, but working from home atm >.>.

In the meanwhile, based on your description of the issue, I managed to work around it by re-grabbing my reference to the object, spline and curve points after running the Add Hook operator.

Thanks for looking into it! Were you able to reproduce it on Linux as well? I could swear that this worked on my work computer just a few days ago... I will check if I get the chance, but working from home atm >.>. In the meanwhile, based on your description of the issue, I managed to work around it by re-grabbing my reference to the object, spline and curve points after running the Add Hook operator.

Germano Cavalcante commented

2020-04-29 13:17:52 +02:00

As far as I can see, there is no simple solution to this.
I don't think it will be resolved anytime soon.

As far as I can see, there is no simple solution to this. I don't think it will be resolved anytime soon.

Demeter Dzadik commented

2020-04-29 15:20:02 +02:00

No worries. For anyone else running into this, some elaboration on the workaround:

This will (or might) fail:

curve_ob = bpy.context.object
for s in curve_ob.data.splines:
    for p in s.bezier_points:
        p.select_control_point = True

        bpy.ops.object.hook_add_selob()

Whereas this should work:

curve_ob = bpy.context.object
for i in range(0, len(curve_ob.data.splines)):
    for p in curve_ob.data.splines[i].bezier_points:
        p.select_control_point = True

        bpy.ops.object.hook_add_selob()
        curve_ob = bpy.context.object

Just refresh your reference to curve_ob(and therefore curve_ob.data) after using the operator.

No worries. For anyone else running into this, some elaboration on the workaround: This will (or might) fail: ``` curve_ob = bpy.context.object for s in curve_ob.data.splines: for p in s.bezier_points: p.select_control_point = True bpy.ops.object.hook_add_selob() ``` Whereas this should work: ``` curve_ob = bpy.context.object for i in range(0, len(curve_ob.data.splines)): for p in curve_ob.data.splines[i].bezier_points: p.select_control_point = True bpy.ops.object.hook_add_selob() curve_ob = bpy.context.object ``` Just refresh your reference to curve_ob(and therefore curve_ob.data) after using the operator.

Demeter Dzadik commented

2020-07-24 12:28:36 +02:00

I have since found out that there is no need to use bpy.ops here, thanks to 3f788eacee. Hook modifiers can be assigned vertices with my_hook_modifier.vertex_indices_set([0, 1, 2]). A much better workaround than what I posted previously, although it does involve reshuffling code a bit more.

I feel like there's no reason to have to call bpy.ops.object.hook_add_selob() from Python anymore. With that in mind I bumped down the priority, but maybe this could even be closed, not sure.

I have since found out that there is no need to use bpy.ops here, thanks to 3f788eacee. Hook modifiers can be assigned vertices with `my_hook_modifier.vertex_indices_set([0, 1, 2])`. A much better workaround than what I posted previously, although it does involve reshuffling code a bit more. I feel like there's no reason to have to call `bpy.ops.object.hook_add_selob()` from Python anymore. With that in mind I bumped down the priority, but maybe this could even be closed, not sure.

Campbell Barton commented

2020-09-18 13:05:06 +02:00

Changed status from 'Confirmed' to: 'Archived'

Campbell Barton closed this issue

2020-09-18 13:05:06 +02:00

Campbell Barton self-assigned this 2020-09-18 13:05:06 +02:00

Campbell Barton commented

2020-09-18 13:05:06 +02:00

Closing since I don't think it's reasonable to consider operators re-allocation of data a bug in the Python API (although from the users perspective I realize it's not very nice).

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Python curve hook operators mess with selection (Probably only on Windows) #74888