bpy.types.SpaceView3D.draw_handler_remove(...) causes Blender to crash #86106
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Reference: blender/blender#86106
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System Information
Operating system: Linux-5.4.0-66-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: Quadro RTX 6000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.102.04
Blender Version
Broken: version: 2.92.0, branch: master, commit date: 2021-02-24 16:25, hash:
02948a2cab
Worked: never
Short description of error
Using bpy.types.SpaceView3D.draw_handler_remove(...) causes Blender to crash.
Exact steps for others to reproduce the error
Original description:
Please execute the python script below.
{F9853647}
The script uses
bpy.types.SpaceView3D.draw_handler_add()
to add a call back function that draws a simple point cloud.The drawing of the point cloud depends on an empty object named
anchor
.If the user deletes this object, the point cloud is no longer drawn (and the call back should be removed with
bpy.types.SpaceView3D.draw_handler_remove(...)
).Currently,
bpy.types.SpaceView3D.draw_handler_remove(...)
is commented out to show this behavior.When uncommenting
bpy.types.SpaceView3D.draw_handler_remove(...)
(see line 80) to remove the callback, Blender crashes.The corresponding error message of
/tmp/blender.crash.txt
can be found in the following file:{F9853675}
Added subscriber: @sbcv
Changed status from 'Needs Triage' to: 'Confirmed'
Added subscriber: @rjg
I'm marking this as confirmed, but given the reference passing of an object that is no longer valid at a later point in time this might be an unsupported use case / a limitation by the Python API (see the Gotchas of the Python API, especially about storing references to objects). However, I believe this is a bug since removing the handler should not be causing the problem, but someone more familiar with the design of the draw handler should take a look at this.
Thank you for having a look at this.
I also thought about this. This is why I tried to keep a reference with
that allows to access the
draw_callback_handler
after the script terminated.Even with the line above, the example script kept crashing. (However, I'm unsure if
bpy.types.Object.current_draw_manager = draw_callback_handler
achieves the intended effect.)Added subscriber: @mano-wii
@mano-wii Thank you for looking into this. Indeed the callback itself removes handler, causing the issue you've identified.
This issue was referenced by
b6c07d69e2
Changed status from 'Confirmed' to: 'Resolved'