Here is another suggestion:

Morph>>delete
"Remove the receiver as a submorph of its owner and make its
new owner be nil."
| oldWorld |
self removeHalo.
self isFlexed ifTrue:[self removeFlexShell].
(oldWorld := self world) ifNotNil: [
self disableSubmorphFocusForHand: self activeHand.
self activeHand
  releaseKeyboardFocus: self;
releaseMouseFocus: self].
owner ifNotNil: [
self privateDelete. "remove from world"
self player ifNotNil: [:player |
oldWorld ifNotNil: [
player noteDeletionOf: self fromWorld: oldWorld]]].

Best,
Karl

On Tue, Sep 24, 2019 at 9:21 AM Marcel Taeumel <marcel.taeumel at hpi.de>
wrote:

> -1 for adding such a side effect to Morph >> #privateDelete.
>
> What about adding TransformMorph >> #removedMorph: and checking for "self
> owner = self world"?
>
> Best,
> Marcel
>
> Am 23.09.2019 22:16:59 schrieb karl ramberg <karlramberg at gmail.com>:
> PS: I have made work around for this issue before in these places:
>
> FlapTab privateDeleteReferent
> MenuMorph delete
> SystemWindow delete
>
> Best,
> Karl
>
> On Mon, Sep 23, 2019 at 10:02 PM karl ramberg <karlramberg at gmail.com>
> wrote:
>
>> I'm not sure if this is the right way to delete a flexed morph.
>> Somebody with a better understanding than me must check if this is the
>> right way to do this.
>> Here is a test that leaves a green TransformationMorph before this change:
>> http://source.squeak.org/inbox/Morphic-kfr.1540.mcz
>>
>> rect := RectangleMorph new openInWorld.
>> rect heading: 45.0.
>> rect delete.
>>
>> Best,
>> Karl.
>>
>> On Mon, Sep 23, 2019 at 9:52 PM <commits at source.squeak.org> wrote:
>>
>>> A new version of Morphic was added to project The Inbox:
>>> http://source.squeak.org/inbox/Morphic-kfr.1540.mcz
>>>
>>> ==================== Summary ====================
>>>
>>> Name: Morphic-kfr.1540
>>> Author: kfr
>>> Time: 23 September 2019, 9:52:14.252115 pm
>>> UUID: 19e57221-4088-0f49-9549-22e1270e933b
>>> Ancestors: Morphic-mt.1539
>>>
>>> If a morph is flexed, it's owner must be deleted
>>>
>>> =============== Diff against Morphic-mt.1539 ===============
>>>
>>> Item was changed:
>>>   ----- Method: Morph>>privateDelete (in category
>>> 'submorphs-add/remove') -----
>>>   privateDelete
>>>         "Remove the receiver as a submorph of its owner"
>>> +       self isFlexed ifTrue:[^owner delete].
>>>         owner ifNotNil:[owner removeMorph: self].!
>>>
>>>
>>>
>
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