Active Spline SubPanel Disappears when editing Bezier Curve (when deleting vertex) #83948

New Issue

William B · 2020-12-19T05:08:12+01:00

William B commented

2020-12-19 05:08:12 +01:00

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 26.20.100.7986

Blender Version
Broken: version: 2.92.0 Alpha, branch: master, commit date: 2020-12-18 23:13, hash: 6942dd9f49
Broken: version: 2.91.0, branch: master, commit date: 2020-11-25 08:34, hash: 0f45cab862

Short description of error
The active spline panel goes away completely during certain curve editing tasks. I have found older reports on the active spline, but those are marked resolved, and this is a specific simple new error that is slightly different.

Exact steps for others to reproduce the error
Make a new "General" blend file. Delete default cube. Add a Curve > Bezier. Tab to Edit. Subdivide curve. Delete the newly added (middle) vertex and at that moment the "Active Spline" goes away.

Re-subdividing doesn't bring the panel back, nor does extruding. Clearly the curve is still present (see image below), and the spline is still present and active, but just a vertex was removed on the curve (that wasn't even an original vertex).

Forgot to add that I absolutely love Blender and all the work you do!!

**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 26.20.100.7986 **Blender Version** Broken: version: 2.92.0 Alpha, branch: master, commit date: 2020-12-18 23:13, hash: `6942dd9f49` Broken: version: 2.91.0, branch: master, commit date: 2020-11-25 08:34, hash: `0f45cab862` **Short description of error** The active spline panel goes away completely during certain curve editing tasks. I have found older reports on the active spline, but those are marked resolved, and this is a specific simple new error that is slightly different. **Exact steps for others to reproduce the error** Make a new "General" blend file. Delete default cube. Add a Curve > Bezier. Tab to Edit. Subdivide curve. Delete the newly added (middle) vertex and at that moment the "Active Spline" goes away. Re-subdividing doesn't bring the panel back, nor does extruding. Clearly the curve is still present (see image below), and the spline is still present and active, but just a vertex was removed on the curve (that wasn't even an original vertex). ![image.png](https://archive.blender.org/developer/F9517221/image.png) Forgot to add that I absolutely love Blender and all the work you do!!

William B commented

2020-12-19 05:08:12 +01:00

Added subscriber: @AquilaTheEagle

Robert Guetzkow commented

2020-12-19 11:26:46 +01:00

Added subscriber: @rjg

Robert Guetzkow commented

2020-12-19 11:26:46 +01:00

I can confirm the behavior. One of the handles or control points needs to be selected afterwards to get the panel back. The problem is that bpy.context.object.data.splines.active is not set after the middle control point / spline is deleted, hence there is no active spline. The panel drawn by DATA_PT_active_spline uses CurveButtonsPanelActive that has the following condition for poll:

    @classmethod
    def poll(cls, context):
        curve = context.curve
        return (curve and type(curve) is not TextCurve and curve.splines.active)

Hence the panel isn't displayed as curve.splines.active is None.

I can confirm the behavior. One of the handles or control points needs to be selected afterwards to get the panel back. The problem is that `bpy.context.object.data.splines.active` is not set after the middle control point / spline is deleted, hence there is no active spline. The panel drawn by `DATA_PT_active_spline` uses `CurveButtonsPanelActive` that has the following condition for poll: ``` @classmethod def poll(cls, context): curve = context.curve return (curve and type(curve) is not TextCurve and curve.splines.active) ``` Hence the panel isn't displayed as `curve.splines.active` is `None`.

Robert Guetzkow commented

2020-12-19 11:38:38 +01:00

I don't think this can considered a bug. The panel is meant to be displayed when there is an active spline and at that moment there isn't one.

This behavior is quite similar to the behavior of the active object with regards to selection and deletion.

I don't think this can considered a bug. The panel is meant to be displayed when there is an active spline and at that moment there isn't one. This behavior is quite similar to the behavior of the active object with regards to selection and deletion.

Robert Guetzkow commented

2020-12-19 11:38:45 +01:00

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

Robert Guetzkow closed this issue

2020-12-19 11:38:45 +01:00

William B commented

2020-12-19 12:06:36 +01:00

Wait . . it is not that simple. On both the daily build and 2.91, selecting a handle, or doing anything does NOT bring the panel back for me.

Select a handle
tab out of edit mode
re-subdivide
extrude a vertex

Also, just deselecting all the handles in edit mode before deleting does not make the panel disappear.

Wait . . it is not that simple. On both the daily build and 2.91, selecting a handle, or doing anything **does NOT bring the panel back for me.** - Select a handle - tab out of edit mode - re-subdivide - extrude a vertex Also, just deselecting all the handles in edit mode before deleting does not make the panel disappear.

Robert Guetzkow commented

2020-12-19 12:28:43 +01:00

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

Robert Guetzkow reopened this issue

2020-12-19 12:28:43 +01:00

Robert Guetzkow commented

2020-12-19 12:33:24 +01:00

I can't reproduce the problem in 2.91 and 2.92 then. What I've done is the following:

Enter edit mode.
Use Segments > Subdivide.
Select the middle part and delete it. As a result the panel disappears.
Select one of the remaining control points / splines and the panel reappears.

That deselecting all handles doesn't make the panel disappear is expected, as just like e.g. with objects there will still be an active object. This a bit of a Blender quirk, but quite consistent across all object types (active != selected).

I can't reproduce the problem in 2.91 and 2.92 then. What I've done is the following: - Enter edit mode. - Use *Segments > Subdivide*. - Select the middle part and delete it. As a result the panel disappears. - Select one of the remaining control points / splines and the panel reappears. That deselecting all handles doesn't make the panel disappear is expected, as just like e.g. with objects there will still be an active object. This a bit of a Blender quirk, but quite consistent across all object types (active != selected).

William B commented

2020-12-19 12:42:08 +01:00

I think I tracked it down a little further . . If I BOX SELECT any vertex, it does NOT reappear. Also, pressing "a" to SELECT ALL after deleting does NOT make it reappear. I tried BOX SELECTING the whole handle (With the arms) or just the central vertex, but neither works.

But if I CLICK the center handle, then it DOES bring back the panel. I didn't expect that BOX SELECTING vs. CLICKING would have a different outcome here.

I think I tracked it down a little further . . If I BOX SELECT any vertex, it does NOT reappear. Also, pressing "a" to SELECT ALL after deleting does NOT make it reappear. I tried BOX SELECTING the whole handle (With the arms) or just the central vertex, but neither works. But if I CLICK the center handle, then it DOES bring back the panel. I didn't expect that BOX SELECTING vs. CLICKING would have a different outcome here.

Hans Goudey commented

2020-12-19 17:27:47 +01:00

Added subscriber: @HooglyBoogly

Hans Goudey commented

2020-12-19 17:27:47 +01:00

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

Hans Goudey closed this issue

2020-12-19 17:27:47 +01:00

Hans Goudey commented

2020-12-19 17:27:47 +01:00

The confusion makes sense, but this really is expected, and it works like this elsewhere in Blender too. Imagine your object has 7 different splines and you box select all of them, which one should be active? Because the choice is completely arbitrary, Blender currently prefers to not make the choice at all. It's the same in object mode, edit mode, etc. Your object with one spline is just a trivial example of this same behavior. There is a task for this, #82359, but it will require some design discussion, as it's pretty fundamental behavior to change and has more implications that you might think.

William B commented

2020-12-19 17:40:56 +01:00

Got it. Thanks for thinking about it! The multi-select makes sense. But BOX SELECTING a single spline or vertex should probably have the same behavior as clicking, right?

Got it. Thanks for thinking about it! The multi-select makes sense. But BOX SELECTING a *single* spline or vertex should probably have the same behavior as clicking, right?

Hans Goudey commented

2020-12-20 18:31:16 +01:00

I suppose that could be a special case. Often it's simpler to keep behavior consistent though, so that it's more predictable in more complicated cases.

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Active Spline SubPanel Disappears when editing Bezier Curve (when deleting vertex) #83948