Bug 481014

Summary:	Renaming of org.kde.kwin.WindowThumbnailItem to WindowThumbnail breaks backwards compatibility for no reason
Product:	[Plasma] kwin	Reporter:	Benjamin Flesch <benjaminflesch>
Component:	core	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED UNMAINTAINED
Severity:	normal	CC:	fanzhuyifan
Priority:	NOR
Version First Reported In:	5.93.0
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Benjamin Flesch 2024-02-07 14:55:32 UTC

SUMMARY
***
WindowSwitcher.qml from custom theme does not work any more. It was because suddenly with v6 "KWin.WindowThumbnailItem" has been renamed to "KWin.WindowThumbnail". 

After renaming the component, the WindowSwitcher works again. 

This naming change is not documented anywhere and it is obviouly not an underlying API change because after renaming, the old component from v5 continues to work. On top of that in KWin source code the whole thing is still called "WindowThumbnailItem.cpp".

WindowThumbnail should be renamed again to WindowThumbnailItem or a copy should be created to increase compabiltiy with v5 WindowSwitcher.qml files.
***


STEPS TO REPRODUCE
1. Spend hours to create a WindowSwitcher.qml for v5
2. Install plasma v6
3. Find out there is a lot of random renaming going on for which you need to spend hours debugging because there is no documentation of the removal and also no documentation what we actually gain from renaming to "WindowThumbnail".

OBSERVED RESULT
Frustrated developers of custom themes

EXPECTED RESULT
Renaming only for real API changes. Depreciation warnings at least for the APIs used in last version. 
If  backwards compatibility is given, a copy with the old name should be created besides the new name.s

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 5.9.3
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION

Comment 1 Benjamin Flesch 2024-02-07 15:00:26 UTC

Breaking change is in: https://github.com/KDE/kwin/commit/9b6c9242f6c4a2a84618511650f992e1e29de9ab

Comment 2 Benjamin Flesch 2024-02-07 15:01:22 UTC

Suggested fix, for the love of god someone just mock WindowThumbnailItem.

Something like this should be added IMO.
```
component WindowThumbnailItem: WindowThumbnail { 
  Component.onComplete: { 
    console.warning("Deprecation warning: WindowThumbnailItem has been renamed to WindowThumbnail")); 
  } 
}
```

Comment 3 fanzhuyifan 2024-02-07 16:54:53 UTC

This isn't critical, critical means "A widespread, easily reproducible issue that causes data loss"

https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

Also marking this as unmaintained since this is private API with no backward-compatibility guarantees. You are welcome to update the wiki to warn 3rd-party developers of this change though.