"ID Data" → "Make Single User" in Outliner for Curve animation data crashes Blender #79187

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System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: Intel(R) Iris(R) Plus Graphics 640 Intel 4.5.0 - Build 26.20.100.7639

Blender Version
Broken: version: 2.83.0 (release), 2.83.3, branch: master, commit date: 2020-07-22 06:01, hash: 353e5bd749
Broken: 2.90 release branch @ ee98dc8d0f
Worked: 2.80, 2.82

Short description of error
Making Curve animation data single-user crashes Blender.

(original report: Linking animation data on curves like keyframed Bevel Start and End values permanenly links animation data and I can't unlink it using "Make Single User" in order to offset curve animation in several curves.)

Exact steps for others to reproduce the error
With Blender in factory defaults:

Create a single curve and duplicate it.
Increase bevel value and animate bevel start and end value with keyframes.
Select both curves, press {key Ctrl L} and link animation data.
Both curves now have same bevel animation.

The above gives you this example file:
#79187-linked_curves-mine.blend

Browse to the Curve action in the BezierCurveAction in the outliner and select it.
Right-click, and depending on the version of Blender:
- 2.82 or older: choose "Make Single User".
- 2.83 or newer: choose "ID Data" → "Make Single User".
Blender 2.83 or newer crashes.

(original report: if you go "Make single User" and select "Animation Data", animation is not unlinked. Changing values on one curve changes animation on all other curves previously linked. In attached file, I replicated the issue and compared it with two mesh cubes. Cubes had their animation data linked, and sucessfuly unlinked and offset so they don't have exact same animation. Curves however curves remain linked. F8715762)

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: Intel(R) Iris(R) Plus Graphics 640 Intel 4.5.0 - Build 26.20.100.7639 **Blender Version** Broken: version: 2.83.0 (release), 2.83.3, branch: master, commit date: 2020-07-22 06:01, hash: `353e5bd749` Broken: 2.90 release branch @ ee98dc8d0f Worked: 2.80, 2.82 **Short description of error** Making Curve animation data single-user crashes Blender. (original report: Linking animation data on curves like keyframed Bevel Start and End values permanenly links animation data and I can't unlink it using "Make Single User" in order to offset curve animation in several curves.) **Exact steps for others to reproduce the error** With Blender in factory defaults: - Create a single curve and duplicate it. - Increase bevel value and animate bevel start and end value with keyframes. - Select both curves, press {key Ctrl L} and link animation data. - Both curves now have same bevel animation. The above gives you this example file: [#79187-linked_curves-mine.blend](https://archive.blender.org/developer/F8716226/T79187-linked_curves-mine.blend) - Browse to the Curve action in the `BezierCurveAction` in the outliner and select it. - Right-click, and depending on the version of Blender: - 2.82 or older: choose "Make Single User". - 2.83 or newer: choose "ID Data" → "Make Single User". - Blender 2.83 or newer crashes. (original report: if you go "Make single User" and select "Animation Data", animation is not unlinked. Changing values on one curve changes animation on all other curves previously linked. In attached file, I replicated the issue and compared it with two mesh cubes. Cubes had their animation data linked, and sucessfuly unlinked and offset so they don't have exact same animation. Curves however curves remain linked. [F8715762](https://archive.blender.org/developer/F8715762/linked_curves.blend))

Added subscriber: @ReljaTrajkovic

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

This seems to be by design. "Make Single User" from the "Object" menu only works on object data. It does not recursively go into the object data. This means that it makes the animation data of the Object single-user but not the animation data of the Curve itself.

You can see this in effect by following these steps:

Create a curve object.
Animate its rotation.
Duplicate the object by using {key Alt D} and move the duplicated curve aside.
Both curve objects now share the same Curve and the same animation data.
Choose "Make Single User" → "Animation Data".
Modifying one object's animation now doesn't influence the other's any more.

Unfortunately, you can't use the Action Editor to make the Curve animation data single-user either, as that only shows object-level actions. It should be possible via the outliner, but that crashes. I'll see if I can fix that crash, so that there is at least some way to make curve animation single-user.

This seems to be by design. "Make Single User" from the "Object" menu only works on object data. It does not recursively go into the object data. This means that it makes the animation data of the Object single-user but not the animation data of the Curve itself. You can see this in effect by following these steps: - Create a curve object. - Animate its rotation. - Duplicate the object by using {key Alt D} and move the duplicated curve aside. - Both curve objects now share the same Curve and the same animation data. - Choose "Make Single User" → "Animation Data". - Modifying one object's animation now doesn't influence the other's any more. Unfortunately, you can't use the Action Editor to make the Curve animation data single-user either, as that only shows object-level actions. It should be possible via the outliner, but that crashes. I'll see if I can fix that crash, so that there is at least some way to make curve animation single-user.

Added subscriber: @dr.sybren

Some developer info:

singleuser_action_cb() is called with tselem->id pointing to the curve Object, instead of the curve itself. This means that further code will not be able to properly find the animation data.
The function then proceeds to use iat->id to find the property that is supposed to be made single-user, but iat->id points to the Scene.

The end result is that IDs are mixed up, and since the Scene doesn't have animation data, Blender segfaults.

Some developer info: `singleuser_action_cb()` is called with `tselem->id` pointing to the curve Object, instead of the curve itself. This means that further code will not be able to properly find the animation data. The function then proceeds to use `iat->id` to find the property that is supposed to be made single-user, but `iat->id` points to the Scene. The end result is that IDs are mixed up, and since the Scene doesn't have animation data, Blender segfaults.

There are two problems here. First, this is a known issue with the outliner context menu that I've started fixing for GSoC in #77770 (Outliner Context Menu Cleanup). The first time I tried replicating the crash I realized what the real issue is:

If BezierCurveAction is first selected with left click, the parent BezierCurve object is also selected. Selecting "ID Data" → "Make Single User" from here causes the crash.

If BezierCurveAction is selected with right click and is the only selected object, the context menu shows like it did in 2.82 with "Make Single User" an immediate option. Running with no objects selected shows that It's a hassle, but a temporary workaround is to ensure that no objects are also selected when running "Make Single User".

The issue is that fixing #74332 (driver can't be seen in the driver editor(blender2.82)) required a selection sync to ensure that parent objects are selected. Pre-2.83 a selection on the curve did not select the parent as it should. Because the parent object is selected, the context menu shows additional entries (requiring the ID Data submenu), and the object is passed to singleuser_action_cb as if it were a curve.

However, this is still a bug in that you can cause this to happen pre 2.83. I tested 2.80 with an additional object selected and the result was still a crash.

singleuser_action_cb is called on all selected elements in the outliner. A simple fix for the crash (which I will commit) is to ensure that the id is an action in the callback.

For the context menu confusion between 2.82 and 2.83+, I'm experimenting in the gsoc outliner branch today to find a quick solution. if there is a nice and easy solution, I think it could also be applied to 2.90 to fix the context menu showing the wrong entries which has caused confusion elsewhere.

There are two problems here. First, this is a known issue with the outliner context menu that I've started fixing for GSoC in #77770 (Outliner Context Menu Cleanup). The first time I tried replicating the crash I realized what the real issue is: If `BezierCurveAction` is first selected with *left click*, the parent `BezierCurve` object is also selected. Selecting "ID Data" → "Make Single User" from here causes the crash. If `BezierCurveAction` is selected with *right click* and is the only selected object, the context menu shows like it did in 2.82 with "Make Single User" an immediate option. Running with no objects selected shows that It's a hassle, but a temporary workaround is to ensure that no objects are also selected when running "Make Single User". The issue is that fixing #74332 (driver can't be seen in the driver editor(blender2.82)) required a selection sync to ensure that parent objects are selected. Pre-2.83 a selection on the curve did not select the parent as it should. Because the parent object is selected, the context menu shows additional entries (requiring the ID Data submenu), and the object is passed to `singleuser_action_cb` as if it were a curve. --- However, this is still a bug in that you can cause this to happen pre 2.83. I tested 2.80 with an additional object selected and the result was still a crash. `singleuser_action_cb` is called on all selected elements in the outliner. A simple fix for the crash (which I will commit) is to ensure that the id is an action in the callback. For the context menu confusion between 2.82 and 2.83+, I'm experimenting in the gsoc outliner branch today to find a quick solution. if there is a nice and easy solution, I think it could also be applied to 2.90 to fix the context menu showing the wrong entries which has caused confusion elsewhere.

This issue was referenced by e48054ece4

This issue was referenced by e48054ece47765c37f55af50922580ee1645f6df

This issue was referenced by 9cbf43801b

This issue was referenced by 9cbf43801ba21b0b4aad0aaccf681ebc7e29cc04

Changed status from 'Confirmed' to: 'Resolved'

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"ID Data" → "Make Single User" in Outliner for Curve animation data crashes Blender #79187