https://bugs.kde.org/show_bug.cgi?id=522261
Bug ID: 522261
Summary: Kdenlive crashes on startup when
project_monitor_fullscreen references a disconnected
monitor
Classification: Applications
Product: kdenlive
Version First 26.04.2
Reported In:
Platform: Other
OS: Microsoft Windows
Status: REPORTED
Severity: normal
Priority: NOR
Component: Monitors & Playback
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 193767
--> https://bugs.kde.org/attachment.cgi?id=193767&action=edit
Technical and forensic investigation reports for the Kdenlive startup crash.
Hello Kdenlive developers,
First of all, thank you for your work on Kdenlive.
I would like to share the results of an investigation I carried out after
encountering a startup crash. Although I am not a software developer, I spent
several days trying to understand what had happened because I wanted to
determine the actual cause instead of simply working around the problem.
### What happened
I was editing a project when Kdenlive suddenly closed unexpectedly.
After that, every time I launched Kdenlive, the recovery dialog appeared
indicating that the previous session had not been closed correctly. However,
regardless of which recovery option I selected, the application always crashed
during startup.
Thinking that the installation might have become corrupted, I completely
uninstalled Kdenlive and installed the latest available version (26.04.2).
Unfortunately, the behavior remained exactly the same: the recovery dialog
still appeared, and the application continued crashing before reaching the main
window.
This problem occurred on **Windows 11**, and only on one Windows user profile.
Creating a brand-new Windows user account allowed Kdenlive to start normally
using the exact same installation.
### Investigation
Since I wanted to understand the problem, I performed a fairly extensive
investigation using:
* Windows Error Reporting (WER)
* WinDbg
* Process Monitor
* Comparison between two Windows user profiles
* Analysis of the Kdenlive source code
* Analysis of the KDDockWidgets source code
* Many controlled experiments by modifying individual configuration values
### What appears to be established
The experiments suggest that:
* The problem is **not** caused by a corrupted installation.
* The standalone build behaves the same way.
* FFmpeg and MLT do not appear to be involved.
* The issue is specific to one Windows user profile.
* Clearing only the persisted `kdockLayout` value does **not** prevent the
crash.
* Clearing only the following configuration entry allows Kdenlive to start
normally:
```ini
[sdl]
project_monitor_fullscreen=1:<monitor identifier>
```
Removing the value of `project_monitor_fullscreen` was sufficient for Kdenlive
to start correctly.
### Current hypothesis
After correlating the experiments with the source code and the WinDbg stack
traces, my current hypothesis is that the automatic restoration of the Project
Monitor in fullscreen during `Monitor::Monitor()` triggers an early
`setParent(nullptr)` operation on the widget hierarchy containing the
`QQuickWidget`.
This seems consistent with the stack traces showing `QWidget::setParent`,
`QQuickWidget`, and `QObject::~QObject`, although I have **not** yet been able
to identify the exact root cause inside the code.
Therefore, I consider this to be the operational trigger, but not yet the
definitive internal root cause.
### Attached report
I have prepared a detailed report describing the investigation, experiments,
stack traces, code paths, and reasoning that led to these conclusions.
I hope it may be useful for diagnosing or reproducing the issue.
Thank you very much for your time, and thank you again for developing Kdenlive.
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