[plasmashell] [Bug 524037] New: Plasmashell crashes (SIGSEGV in Plasma::Containment::corona()) after monitor switch, leaving desktop icons missing on restart

https://bugs.kde.org/show_bug.cgi?id=524037

            Bug ID: 524037
           Summary: Plasmashell crashes (SIGSEGV in
                    Plasma::Containment::corona()) after monitor switch,
                    leaving desktop icons missing on restart
    Classification: Plasma
           Product: plasmashell
      Version First 6.6.6
       Reported In:
          Platform: Ubuntu
                OS: Linux
            Status: REPORTED
          Severity: crash
          Priority: NOR
         Component: Containment
          Assignee: [email protected]
          Reporter: [email protected]
                CC: [email protected]
  Target Milestone: 1.0

Summary: Plasmashell crashes (SIGSEGV in Plasma::Containment::corona()) after
monitor switch, leaving desktop icons missing on restart

Application: plasmashell
Version: 6.6.6 (Ubuntu package 4:6.6.6-0ubuntu0.1)
Qt Version: 6.10.2
Frameworks Version: 6.24.0
Operating System: Kubuntu 26.06 (Wayland session)
Distribution: Ubuntu 26.06 "Resolute"

Hardware: Laptop (HP15) with external HDMI monitor (dual-monitor setup, laptop
panel eDP-1 + external HDMI-A-1)

---

Summary of the issue:

After switching between the laptop's internal display and an external HDMI
monitor (disabling one output while the other is active), plasmashell
segfaults. Following the crash, desktop icons no longer appear on either
display -- even after restarting plasmashell or fully rebooting the system.

Steps to reproduce:
1. Start a Plasma Wayland session with both an internal laptop panel (eDP-1)
and an external HDMI monitor (HDMI-A-1) available.
2. Switch active output -- e.g. disable the laptop panel and use HDMI-only, or
vice versa.
3. Continue using the desktop normally (clicking panel items, desktop context
menu, etc.)
4. Plasmashell crashes with SIGSEGV.
5. After crash/restart, desktop icons are missing on all displays, even though
the underlying ~/.config/plasma-org.kde.plasma.desktop-appletsrc file still
contains valid, intact icon position data for the "Desktop folder" containment.

Observed root cause (from journal logs):
Before the crash, the following errors appear repeatedly in the logs when
switching outputs:

qt.qpa.wayland: There are no outputs - creating placeholder screen
kde.plasmashell: requesting unexisting screen available rect -1

This suggests an orphaned/duplicate desktop containment gets created bound to a
screen index (lastScreen=) that no longer has a valid output, alongside the
original valid containment bound to a different screen index. In the appletsrc
file, this was observed as two [Containments] sections using the same plugin
(org.kde.plasma.folder) -- one fully populated with icon geometry/wallpaper
config, the other empty, bound to lastScreen=1 vs lastScreen=0.

Crash backtrace (via coredumpctl / gdb):

Stack trace of thread (main):
#4  Plasma::Containment::corona() const (libPlasma.so.7)
#5  plasmashell + 0x3cd06
#6  plasmashell + 0x3f447
#7-9 QV4::QObjectMethod::callPrecise / callInternal (libQt6Qml.so.6)
...
#25 QQuickAction::triggered(QObject*) (libQt6QuickTemplates2.so.6)
...
#55 QQuickAbstractButtonPrivate::handleRelease (libQt6QuickTemplates2.so.6)
#56 QQuickControl::mouseReleaseEvent (libQt6QuickTemplates2.so.6)

The crash occurs in Plasma::Containment::corona(), triggered by a QQuickAction
signal following a button/mouse release event -- consistent with a dangling or
null Containment pointer being dereferenced after an output/screen was removed.

Expected behavior: Switching monitor outputs should not create orphaned
containments or crash plasmashell; if a screen becomes unavailable, its
containment should be gracefully reassigned or hidden rather than left as a
dangling reference.

Actual behavior: Plasmashell segfaults; desktop icons disappear from all
screens afterward, requiring manual/config-level intervention to identify
(though not yet reliably fix) the cause.

Additional info: Full coredumpctl info output and complete backtrace available
on request; the crashing process was PID 4533, package plasma-workspace
4:6.6.6-0ubuntu0.1.

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