What are you using that shows those lines?

(In reply to Kurt Hindenburg from comment #1)
> What are you using that shows those lines?

Breeze::WidgetExplorer::eventFilter

https://github.com/KDE/breeze/blob/master/kstyle/debug/breezewidgetexplorer.cpp

https://github.com/KDE/breeze/blob/master/kstyle/breeze.kcfg#L181

Also I think this is the reason for https://bugs.kde.org/show_bug.cgi?id=411741

The ViewSplitter is destroyed as soon as all of their children are destroyed. From the picture I can see that you first did a horizontal split and then a vertical split, closing 0 kills the Terminal there, but the split is still alive as it holds Terminal 1 / 2. Closing 1 still keeps the splitter alive as it holds 2. If you killed 2 and 1, on the other hand, the internal splitter deletes itself.

I'll take a look to see how complex is to simplify the split hierarchy after a terminal has been removed

"how complex is to simplify" (best sentence ever)
Most complex thing for any developer :) :) :)

pseudo code idea

void afterTerminalDetached () {
    if (this->childrenCount == 1 && this->child(0).class == "ViewSplitter") {
        auto child = this->child(0);
        this->parent().swap(this, child);
    }
}

pseudocode seems nice, I'll try to implement something like that on the weekend.

Created attachment 123271 [details]
ugly patch

Working ugly patch/hack

Also this fix/resolve #411741

Created attachment 123274 [details]
attachment-905-0.html

Really thanks for getting your hands dirty :)
I'll do a test today on it. the code seems a bit fragile but sometimes code
will be fragile no matter what.

On Thu, Oct 17, 2019 at 1:47 PM Nikolay Zlatev <bugzilla_noreply@kde.org>
wrote:

> https://bugs.kde.org/show_bug.cgi?id=412596
>
> --- Comment #7 from Nikolay Zlatev <nik@astrapaging.com> ---
> Created attachment 123271 [details]
>   --> https://bugs.kde.org/attachment.cgi?id=123271&action=edit
> ugly patch
>
> Working ugly patch/hack
>
> Also this fix/resolve #411741
>
> --
> You are receiving this mail because:
> You are on the CC list for the bug.

Created attachment 123276 [details]
Patch v2

This is one of the ugliest code i have wrote.

Told you that it was non trivial. :)

Tomaz, do you agree w/ the patch as-is or do you have any suggestions?

Git commit c33eba8c60b99d00cd73c400d23b6f338ef32a85 by Kurt Hindenburg, on behalf of Carlos Alves.
Committed on 02/11/2020 at 18:14.
Pushed by hindenburg into branch 'master'.

Fix konsole crashes when rearranging split views

I'll try to explain here what I saw in this bug.
Following the BUG instructions, drag the terminal[2] and drop
(here the "drop event" starts)
-> the dragged terminal "ViewSplitter" become scheduled for deletion,
but it will only happens when it is in event loop.
-> And of course it is not in event loop yet, it is still the
"drop event" and it call the "addTerminalDisplay" to add the dragged
 terminal to a "ViewSplitter".
-> This makes count() counts this scheduled for deletion "ViewSplitter"
 and goes to the wrong "if".
-> It adds the "ViewSplitter" with the terminals into a
"marked for deletion" one, finishes the "drop event" and enters
event loop (a crash without a memleak! everything in the tab
 is properly deleted).
Related: bug 411741
FIXED-IN: 20.12

M  +4    -0    src/widgets/ViewSplitter.cpp

https://invent.kde.org/utilities/konsole/commit/c33eba8c60b99d00cd73c400d23b6f338ef32a85

(In reply to Kurt Hindenburg from comment #12)
> Git commit c33eba8c60b99d00cd73c400d23b6f338ef32a85 by Kurt Hindenburg, on
> behalf of Carlos Alves.
> Committed on 02/11/2020 at 18:14.
> Pushed by hindenburg into branch 'master'.
> 
> Fix konsole crashes when rearranging split views
> 
> I'll try to explain here what I saw in this bug.
> Following the BUG instructions, drag the terminal[2] and drop
> (here the "drop event" starts)
> -> the dragged terminal "ViewSplitter" become scheduled for deletion,
> but it will only happens when it is in event loop.
> -> And of course it is not in event loop yet, it is still the
> "drop event" and it call the "addTerminalDisplay" to add the dragged
>  terminal to a "ViewSplitter".
> -> This makes count() counts this scheduled for deletion "ViewSplitter"
>  and goes to the wrong "if".
> -> It adds the "ViewSplitter" with the terminals into a
> "marked for deletion" one, finishes the "drop event" and enters
> event loop (a crash without a memleak! everything in the tab
>  is properly deleted).
> Related: bug 411741
> FIXED-IN: 20.12
> 
> M  +4    -0    src/widgets/ViewSplitter.cpp
> 
> https://invent.kde.org/utilities/konsole/commit/
> c33eba8c60b99d00cd73c400d23b6f338ef32a85


This commit doesn't fix the issue described here

Parent tree
Breeze::WidgetExplorer::eventFilter widget: 0x557e59a12c10 (Konsole::TerminalDisplay)
    parent: 0x557e59d8db80 (Konsole::ViewSplitter)
    parent: 0x557e59cc6800 (Konsole::ViewSplitter)
    parent: 0x557e599aeb10 (Konsole::ViewSplitter)
    parent: 0x557e59925c90 (Konsole::ViewSplitter)
    parent: 0x557e59926070 (Konsole::ViewSplitter)
    parent: 0x557e595eb2f0 (Konsole::ViewSplitter)
    parent: 0x557e59b450a0 (Konsole::ViewSplitter)
    parent: 0x557e59aa0c80 (Konsole::ViewSplitter)
    parent: 0x557e59a00230 (Konsole::ViewSplitter)
    parent: 0x557e5984ada0 (Konsole::ViewSplitter)
    parent: 0x557e59970f30 (Konsole::ViewSplitter)
    parent: 0x557e599c28c0 (Konsole::ViewSplitter)
    parent: 0x557e5962a530 (Konsole::ViewSplitter)
    parent: 0x557e5946ba10 (QStackedWidget)
    parent: 0x557e59424510 (Konsole::TabbedViewContainer)
    parent: 0x557e594143e0 (Konsole::MainWindow)

the viewsplitter is destroyed when there's nothing inside of it.
those viewsplitters are still holding the internal view splitter that ultimately holds a Terminal. 

The memory loss is negligigle, it does not introduces crashes or leaks, there's no user visible issues on because of that

But I agree that it would be nice to fix, and I agree that the original issue is not fixed.